Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi Matthias,

Sorry for long delay. Thanks for the comment. Good to know that the
specified issue is not worth to break the backwards-compatibility.
I fixed the KIP.

Cheers,
Jeyhun

On Fri, Jun 30, 2017 at 1:38 AM Matthias J. Sax 
wrote:

> Hi Jeyhun,
>
> thanks for starting the VOTE thread. I did make one more pass over the
> KIP before casting my vote and I saw that the KIP still contains
> backward incompatible change introducing `ValueTransformerCommon`.
>
> I think, that for this case, it is not worth breaking compatibility. We
> should have two independent interface and duplicate init() and close()
> (note, with KIP-138 that got merged already, we don't need `punctuate()`
> for ValueTransformerWithKey)
>
>
> -Matthias
>
> On 6/14/17 3:03 PM, Matthias J. Sax wrote:
> > I have no strong opinion, but it seems that at least InitializerWithKey
> > with be helpful if you want to have different start values for different
> > keys (even if I cannot come up with a use case example why one wanted to
> > do this...). Otherwise, there is just the "completeness" argument, that
> > is not too strong either.
> >
> >
> > -Matthias
> >
> > On 6/14/17 2:03 PM, Guozhang Wang wrote:
> >> I'm not particularly concerning that we should NEVER break
> compatibility;
> >> in fact if we think that is worthwhile (i.e. small impact with large
> >> benefit) I think we can break compatibility as long as we have not
> removed
> >> the compatibility annotations from Streams. All I was saying is that if
> we
> >> decided to go this way we need to make sure this is mentioned in the
> >> upgrade guidance.
> >>
> >> Regarding the scope I'm still trying to solicit opinions regarding
> >> ReducerWithKey and InitializerWithKey; to me they are not necessarily
> to be
> >> included.
> >>
> >>
> >> Guozhang
> >>
> >>
> >> On Wed, Jun 14, 2017 at 5:22 AM, Jeyhun Karimov 
> >> wrote:
> >>
> >>> Hi,
> >>>
> >>> I introduced ValueTransformerCommon just to combine common methods of
> >>> ValueTransformer and ValueTransformerWithKey and avoid copy-paste.
> >>> I am aware of this issue and I agree that this needs users to compile
> the
> >>> code and therefore is not backwards compatible. When I saw this issue,
> I
> >>> thought the degree of incompatibility is small (the public APIs are the
> >>> same, users just need to recompile their code), so we can trade more
> >>> maintainable code in this case. I have to comments/solutions:
> >>>
> >>> 1. Basically we can remove ValueTransformerCommon class and return
> >>> ValueTransformer to its original form, which means there will be no
> issues
> >>> with backwards-compatibility. We just copy and past the methods inside
> >>> ValueTransformerCommon to ValueTransformerWithKey and maybe in future
> >>> releases, we can introduce ValueTransformerCommon.
> >>>
> >>> 2.  I have some doubts about Matthias's proposal.
> >>> If we extent withKey interface from original one   as you mentioned in
> >>> previous email, then we have to deal with
> >>>  ValueTransformer.transform(V value) method. As a result, inside
> withKey
> >>> interface we will have two transforms. Even if we make it abstract
> class,
> >>> user still have an access to play with both transform() methods. I
> think
> >>> this should not be allowed and seems "hacky" to me. Actually this was
> one
> >>> reason why I created withKey classes independently from original
> >>> interfaces.
> >>>
> >>> Of course, you can correct me if I am wrong.
> >>>
> >>>
> >>> Cheers,
> >>> Jeyhun
> >>>
> >>>
> >>>
> >>> On Tue, Jun 13, 2017 at 7:42 PM Matthias J. Sax  >
> >>> wrote:
> >>>
>  I agree with Guozhang's second point. This change does not seem
> backward
>  compatible.
> 
>  As we don't have to support lambdas, it might be the easiest thing to
>  just extend the current interface:
> 
> > public interface ValueTransformerWithKey extends
>  ValueTransformer
> 
>  When plugging the topology together, we can check if we get the
>  `withKey` variant and use a corresponding runtime class for execution,
>  so we get only a single time check. Thus, for the `withKey` variant,
> the
>  will be a `transfrom(V value)` method, but we will never call it.
> 
>  Maybe we could make `ValueTransformerWithKey` an abstract class with a
>  `final` no-op implemenation of `transform(V value)` ?
> 
> 
>  -Matthias
> 
> 
>  On 6/6/17 4:58 PM, Guozhang Wang wrote:
> > Jeyhun, Matthias:
> >
> > Thanks for the explanation, I overlooked the repartition argument
> > previously.
> >
> > 1) Based on that argument I'm convinced of having ValueMapperWithKey
> /
> > ValueJoinerWithKey / ValueTransformerWithKey; though I'm still not
> > convinced with ReducerWithKey and InitializerWithKey since for the
> >>> former
> > it can be covered with `aggregate` completely and with latter I have

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Hi Jeyhun,

thanks for starting the VOTE thread. I did make one more pass over the
KIP before casting my vote and I saw that the KIP still contains
backward incompatible change introducing `ValueTransformerCommon`.

I think, that for this case, it is not worth breaking compatibility. We
should have two independent interface and duplicate init() and close()
(note, with KIP-138 that got merged already, we don't need `punctuate()`
for ValueTransformerWithKey)


-Matthias

On 6/14/17 3:03 PM, Matthias J. Sax wrote:
> I have no strong opinion, but it seems that at least InitializerWithKey
> with be helpful if you want to have different start values for different
> keys (even if I cannot come up with a use case example why one wanted to
> do this...). Otherwise, there is just the "completeness" argument, that
> is not too strong either.
> 
> 
> -Matthias
> 
> On 6/14/17 2:03 PM, Guozhang Wang wrote:
>> I'm not particularly concerning that we should NEVER break compatibility;
>> in fact if we think that is worthwhile (i.e. small impact with large
>> benefit) I think we can break compatibility as long as we have not removed
>> the compatibility annotations from Streams. All I was saying is that if we
>> decided to go this way we need to make sure this is mentioned in the
>> upgrade guidance.
>>
>> Regarding the scope I'm still trying to solicit opinions regarding
>> ReducerWithKey and InitializerWithKey; to me they are not necessarily to be
>> included.
>>
>>
>> Guozhang
>>
>>
>> On Wed, Jun 14, 2017 at 5:22 AM, Jeyhun Karimov 
>> wrote:
>>
>>> Hi,
>>>
>>> I introduced ValueTransformerCommon just to combine common methods of
>>> ValueTransformer and ValueTransformerWithKey and avoid copy-paste.
>>> I am aware of this issue and I agree that this needs users to compile the
>>> code and therefore is not backwards compatible. When I saw this issue, I
>>> thought the degree of incompatibility is small (the public APIs are the
>>> same, users just need to recompile their code), so we can trade more
>>> maintainable code in this case. I have to comments/solutions:
>>>
>>> 1. Basically we can remove ValueTransformerCommon class and return
>>> ValueTransformer to its original form, which means there will be no issues
>>> with backwards-compatibility. We just copy and past the methods inside
>>> ValueTransformerCommon to ValueTransformerWithKey and maybe in future
>>> releases, we can introduce ValueTransformerCommon.
>>>
>>> 2.  I have some doubts about Matthias's proposal.
>>> If we extent withKey interface from original one   as you mentioned in
>>> previous email, then we have to deal with
>>>  ValueTransformer.transform(V value) method. As a result, inside withKey
>>> interface we will have two transforms. Even if we make it abstract class,
>>> user still have an access to play with both transform() methods. I think
>>> this should not be allowed and seems "hacky" to me. Actually this was one
>>> reason why I created withKey classes independently from original
>>> interfaces.
>>>
>>> Of course, you can correct me if I am wrong.
>>>
>>>
>>> Cheers,
>>> Jeyhun
>>>
>>>
>>>
>>> On Tue, Jun 13, 2017 at 7:42 PM Matthias J. Sax 
>>> wrote:
>>>
 I agree with Guozhang's second point. This change does not seem backward
 compatible.

 As we don't have to support lambdas, it might be the easiest thing to
 just extend the current interface:

> public interface ValueTransformerWithKey extends
 ValueTransformer

 When plugging the topology together, we can check if we get the
 `withKey` variant and use a corresponding runtime class for execution,
 so we get only a single time check. Thus, for the `withKey` variant, the
 will be a `transfrom(V value)` method, but we will never call it.

 Maybe we could make `ValueTransformerWithKey` an abstract class with a
 `final` no-op implemenation of `transform(V value)` ?


 -Matthias


 On 6/6/17 4:58 PM, Guozhang Wang wrote:
> Jeyhun, Matthias:
>
> Thanks for the explanation, I overlooked the repartition argument
> previously.
>
> 1) Based on that argument I'm convinced of having ValueMapperWithKey /
> ValueJoinerWithKey / ValueTransformerWithKey; though I'm still not
> convinced with ReducerWithKey and InitializerWithKey since for the
>>> former
> it can be covered with `aggregate` completely and with latter I have
>>> seen
> little use cases with it.
>
> 2) Another comment is on public interface ValueTransformer
>>> extends
> ValueTransformerCommon:
>
> I think changing the interface to extend from a new interface is not
 binary
> compatible though source compatible, i.e. users still need to recompile
> their code though no need to make code changes. We may need to mention
 that
> in the upgrade path if we want to keep it that way.
>
> Guozhang
>
> 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

I have no strong opinion, but it seems that at least InitializerWithKey
with be helpful if you want to have different start values for different
keys (even if I cannot come up with a use case example why one wanted to
do this...). Otherwise, there is just the "completeness" argument, that
is not too strong either.


-Matthias

On 6/14/17 2:03 PM, Guozhang Wang wrote:
> I'm not particularly concerning that we should NEVER break compatibility;
> in fact if we think that is worthwhile (i.e. small impact with large
> benefit) I think we can break compatibility as long as we have not removed
> the compatibility annotations from Streams. All I was saying is that if we
> decided to go this way we need to make sure this is mentioned in the
> upgrade guidance.
> 
> Regarding the scope I'm still trying to solicit opinions regarding
> ReducerWithKey and InitializerWithKey; to me they are not necessarily to be
> included.
> 
> 
> Guozhang
> 
> 
> On Wed, Jun 14, 2017 at 5:22 AM, Jeyhun Karimov 
> wrote:
> 
>> Hi,
>>
>> I introduced ValueTransformerCommon just to combine common methods of
>> ValueTransformer and ValueTransformerWithKey and avoid copy-paste.
>> I am aware of this issue and I agree that this needs users to compile the
>> code and therefore is not backwards compatible. When I saw this issue, I
>> thought the degree of incompatibility is small (the public APIs are the
>> same, users just need to recompile their code), so we can trade more
>> maintainable code in this case. I have to comments/solutions:
>>
>> 1. Basically we can remove ValueTransformerCommon class and return
>> ValueTransformer to its original form, which means there will be no issues
>> with backwards-compatibility. We just copy and past the methods inside
>> ValueTransformerCommon to ValueTransformerWithKey and maybe in future
>> releases, we can introduce ValueTransformerCommon.
>>
>> 2.  I have some doubts about Matthias's proposal.
>> If we extent withKey interface from original one   as you mentioned in
>> previous email, then we have to deal with
>>  ValueTransformer.transform(V value) method. As a result, inside withKey
>> interface we will have two transforms. Even if we make it abstract class,
>> user still have an access to play with both transform() methods. I think
>> this should not be allowed and seems "hacky" to me. Actually this was one
>> reason why I created withKey classes independently from original
>> interfaces.
>>
>> Of course, you can correct me if I am wrong.
>>
>>
>> Cheers,
>> Jeyhun
>>
>>
>>
>> On Tue, Jun 13, 2017 at 7:42 PM Matthias J. Sax 
>> wrote:
>>
>>> I agree with Guozhang's second point. This change does not seem backward
>>> compatible.
>>>
>>> As we don't have to support lambdas, it might be the easiest thing to
>>> just extend the current interface:
>>>
 public interface ValueTransformerWithKey extends
>>> ValueTransformer
>>>
>>> When plugging the topology together, we can check if we get the
>>> `withKey` variant and use a corresponding runtime class for execution,
>>> so we get only a single time check. Thus, for the `withKey` variant, the
>>> will be a `transfrom(V value)` method, but we will never call it.
>>>
>>> Maybe we could make `ValueTransformerWithKey` an abstract class with a
>>> `final` no-op implemenation of `transform(V value)` ?
>>>
>>>
>>> -Matthias
>>>
>>>
>>> On 6/6/17 4:58 PM, Guozhang Wang wrote:
 Jeyhun, Matthias:

 Thanks for the explanation, I overlooked the repartition argument
 previously.

 1) Based on that argument I'm convinced of having ValueMapperWithKey /
 ValueJoinerWithKey / ValueTransformerWithKey; though I'm still not
 convinced with ReducerWithKey and InitializerWithKey since for the
>> former
 it can be covered with `aggregate` completely and with latter I have
>> seen
 little use cases with it.

 2) Another comment is on public interface ValueTransformer
>> extends
 ValueTransformerCommon:

 I think changing the interface to extend from a new interface is not
>>> binary
 compatible though source compatible, i.e. users still need to recompile
 their code though no need to make code changes. We may need to mention
>>> that
 in the upgrade path if we want to keep it that way.

 Guozhang

 On Mon, Jun 5, 2017 at 2:28 PM, Jeyhun Karimov 
>>> wrote:

> Hi,
>
>
> Sorry for late reply. Just to make everybody in sync, the current
>>> version
> of KIP supports lambdas. "withKey" (ValueMapperWithKey) interfaces are
> independent, meaning they do not extend from "withoutKey"
>> (ValueMapper)
> interfaces.
>
>
> I agree with Guozhang, and I am personally a bit reluctant to increase
> overloaded methods in public APIs but it seems this is only way to
>> solve
> all related jira issues.
> However, the most overloaded methods will be with 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Guozhang Wang]

I'm not particularly concerning that we should NEVER break compatibility;
in fact if we think that is worthwhile (i.e. small impact with large
benefit) I think we can break compatibility as long as we have not removed
the compatibility annotations from Streams. All I was saying is that if we
decided to go this way we need to make sure this is mentioned in the
upgrade guidance.

Regarding the scope I'm still trying to solicit opinions regarding
ReducerWithKey and InitializerWithKey; to me they are not necessarily to be
included.


Guozhang


On Wed, Jun 14, 2017 at 5:22 AM, Jeyhun Karimov 
wrote:

> Hi,
>
> I introduced ValueTransformerCommon just to combine common methods of
> ValueTransformer and ValueTransformerWithKey and avoid copy-paste.
> I am aware of this issue and I agree that this needs users to compile the
> code and therefore is not backwards compatible. When I saw this issue, I
> thought the degree of incompatibility is small (the public APIs are the
> same, users just need to recompile their code), so we can trade more
> maintainable code in this case. I have to comments/solutions:
>
> 1. Basically we can remove ValueTransformerCommon class and return
> ValueTransformer to its original form, which means there will be no issues
> with backwards-compatibility. We just copy and past the methods inside
> ValueTransformerCommon to ValueTransformerWithKey and maybe in future
> releases, we can introduce ValueTransformerCommon.
>
> 2.  I have some doubts about Matthias's proposal.
> If we extent withKey interface from original one   as you mentioned in
> previous email, then we have to deal with
>  ValueTransformer.transform(V value) method. As a result, inside withKey
> interface we will have two transforms. Even if we make it abstract class,
> user still have an access to play with both transform() methods. I think
> this should not be allowed and seems "hacky" to me. Actually this was one
> reason why I created withKey classes independently from original
> interfaces.
>
> Of course, you can correct me if I am wrong.
>
>
> Cheers,
> Jeyhun
>
>
>
> On Tue, Jun 13, 2017 at 7:42 PM Matthias J. Sax 
> wrote:
>
> > I agree with Guozhang's second point. This change does not seem backward
> > compatible.
> >
> > As we don't have to support lambdas, it might be the easiest thing to
> > just extend the current interface:
> >
> > > public interface ValueTransformerWithKey extends
> > ValueTransformer
> >
> > When plugging the topology together, we can check if we get the
> > `withKey` variant and use a corresponding runtime class for execution,
> > so we get only a single time check. Thus, for the `withKey` variant, the
> > will be a `transfrom(V value)` method, but we will never call it.
> >
> > Maybe we could make `ValueTransformerWithKey` an abstract class with a
> > `final` no-op implemenation of `transform(V value)` ?
> >
> >
> > -Matthias
> >
> >
> > On 6/6/17 4:58 PM, Guozhang Wang wrote:
> > > Jeyhun, Matthias:
> > >
> > > Thanks for the explanation, I overlooked the repartition argument
> > > previously.
> > >
> > > 1) Based on that argument I'm convinced of having ValueMapperWithKey /
> > > ValueJoinerWithKey / ValueTransformerWithKey; though I'm still not
> > > convinced with ReducerWithKey and InitializerWithKey since for the
> former
> > > it can be covered with `aggregate` completely and with latter I have
> seen
> > > little use cases with it.
> > >
> > > 2) Another comment is on public interface ValueTransformer
> extends
> > > ValueTransformerCommon:
> > >
> > > I think changing the interface to extend from a new interface is not
> > binary
> > > compatible though source compatible, i.e. users still need to recompile
> > > their code though no need to make code changes. We may need to mention
> > that
> > > in the upgrade path if we want to keep it that way.
> > >
> > > Guozhang
> > >
> > > On Mon, Jun 5, 2017 at 2:28 PM, Jeyhun Karimov 
> > wrote:
> > >
> > >> Hi,
> > >>
> > >>
> > >> Sorry for late reply. Just to make everybody in sync, the current
> > version
> > >> of KIP supports lambdas. "withKey" (ValueMapperWithKey) interfaces are
> > >> independent, meaning they do not extend from "withoutKey"
> (ValueMapper)
> > >> interfaces.
> > >>
> > >>
> > >> I agree with Guozhang, and I am personally a bit reluctant to increase
> > >> overloaded methods in public APIs but it seems this is only way to
> solve
> > >> all related jira issues.
> > >> However, the most overloaded methods will be with ValueJoiner type,
> > which
> > >> will be with ValueJoinerWithKey with new overloaded methods. Other
> > >> interfaces require mostly 1 extra overload.
> > >>
> > >>
> >  I would suggest not doing it if user pop it up, but rather
> suggesting
> > >> them
> >  to use `map`
> > >>
> > >> I agree with Matthias as the core idea of this KIP was to collect all
> > >> related jira issues and propose one-shot 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi,

I introduced ValueTransformerCommon just to combine common methods of
ValueTransformer and ValueTransformerWithKey and avoid copy-paste.
I am aware of this issue and I agree that this needs users to compile the
code and therefore is not backwards compatible. When I saw this issue, I
thought the degree of incompatibility is small (the public APIs are the
same, users just need to recompile their code), so we can trade more
maintainable code in this case. I have to comments/solutions:

1. Basically we can remove ValueTransformerCommon class and return
ValueTransformer to its original form, which means there will be no issues
with backwards-compatibility. We just copy and past the methods inside
ValueTransformerCommon to ValueTransformerWithKey and maybe in future
releases, we can introduce ValueTransformerCommon.

2.  I have some doubts about Matthias's proposal.
If we extent withKey interface from original one   as you mentioned in
previous email, then we have to deal with
 ValueTransformer.transform(V value) method. As a result, inside withKey
interface we will have two transforms. Even if we make it abstract class,
user still have an access to play with both transform() methods. I think
this should not be allowed and seems "hacky" to me. Actually this was one
reason why I created withKey classes independently from original
interfaces.

Of course, you can correct me if I am wrong.


Cheers,
Jeyhun



On Tue, Jun 13, 2017 at 7:42 PM Matthias J. Sax 
wrote:

> I agree with Guozhang's second point. This change does not seem backward
> compatible.
>
> As we don't have to support lambdas, it might be the easiest thing to
> just extend the current interface:
>
> > public interface ValueTransformerWithKey extends
> ValueTransformer
>
> When plugging the topology together, we can check if we get the
> `withKey` variant and use a corresponding runtime class for execution,
> so we get only a single time check. Thus, for the `withKey` variant, the
> will be a `transfrom(V value)` method, but we will never call it.
>
> Maybe we could make `ValueTransformerWithKey` an abstract class with a
> `final` no-op implemenation of `transform(V value)` ?
>
>
> -Matthias
>
>
> On 6/6/17 4:58 PM, Guozhang Wang wrote:
> > Jeyhun, Matthias:
> >
> > Thanks for the explanation, I overlooked the repartition argument
> > previously.
> >
> > 1) Based on that argument I'm convinced of having ValueMapperWithKey /
> > ValueJoinerWithKey / ValueTransformerWithKey; though I'm still not
> > convinced with ReducerWithKey and InitializerWithKey since for the former
> > it can be covered with `aggregate` completely and with latter I have seen
> > little use cases with it.
> >
> > 2) Another comment is on public interface ValueTransformer extends
> > ValueTransformerCommon:
> >
> > I think changing the interface to extend from a new interface is not
> binary
> > compatible though source compatible, i.e. users still need to recompile
> > their code though no need to make code changes. We may need to mention
> that
> > in the upgrade path if we want to keep it that way.
> >
> > Guozhang
> >
> > On Mon, Jun 5, 2017 at 2:28 PM, Jeyhun Karimov 
> wrote:
> >
> >> Hi,
> >>
> >>
> >> Sorry for late reply. Just to make everybody in sync, the current
> version
> >> of KIP supports lambdas. "withKey" (ValueMapperWithKey) interfaces are
> >> independent, meaning they do not extend from "withoutKey" (ValueMapper)
> >> interfaces.
> >>
> >>
> >> I agree with Guozhang, and I am personally a bit reluctant to increase
> >> overloaded methods in public APIs but it seems this is only way to solve
> >> all related jira issues.
> >> However, the most overloaded methods will be with ValueJoiner type,
> which
> >> will be with ValueJoinerWithKey with new overloaded methods. Other
> >> interfaces require mostly 1 extra overload.
> >>
> >>
>  I would suggest not doing it if user pop it up, but rather suggesting
> >> them
>  to use `map`
> >>
> >> I agree with Matthias as the core idea of this KIP was to collect all
> >> related jira issues and propose one-shot solution for all. Afterwards,
> we
> >> broke its scope into 2 KIPs (149 and 159).
> >>
> >> Cheers,
> >> Jeyhun
> >>
> >>
> >>
> >> On Mon, Jun 5, 2017 at 7:55 AM Matthias J. Sax 
> >> wrote:
> >>
> >>> I guess I missunderstood you. Your are right that overloading the
> method
> >>> would also work. As both interfaces will be independent from each
> other,
> >>> there should be no problem.
> >>>
> >>> The initial proposal was to use
> >>>
>  interface ValueMapperWithKey extends ValueMapper
> >>>
> >>> and this would break Lambda. We totally missed, that we don't need new
> >>> methods but only only overlaods. Great you point this out! I was not
> >>> quite happy with the newly added methods.
> >>>
> > I would suggest not doing it if user pop it up, but rather suggesting
> >>> them
> > to use `map`
> >>>
> 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

I agree with Guozhang's second point. This change does not seem backward
compatible.

As we don't have to support lambdas, it might be the easiest thing to
just extend the current interface:

> public interface ValueTransformerWithKey extends 
> ValueTransformer 

When plugging the topology together, we can check if we get the
`withKey` variant and use a corresponding runtime class for execution,
so we get only a single time check. Thus, for the `withKey` variant, the
will be a `transfrom(V value)` method, but we will never call it.

Maybe we could make `ValueTransformerWithKey` an abstract class with a
`final` no-op implemenation of `transform(V value)` ?


-Matthias


On 6/6/17 4:58 PM, Guozhang Wang wrote:
> Jeyhun, Matthias:
> 
> Thanks for the explanation, I overlooked the repartition argument
> previously.
> 
> 1) Based on that argument I'm convinced of having ValueMapperWithKey /
> ValueJoinerWithKey / ValueTransformerWithKey; though I'm still not
> convinced with ReducerWithKey and InitializerWithKey since for the former
> it can be covered with `aggregate` completely and with latter I have seen
> little use cases with it.
> 
> 2) Another comment is on public interface ValueTransformer extends
> ValueTransformerCommon:
> 
> I think changing the interface to extend from a new interface is not binary
> compatible though source compatible, i.e. users still need to recompile
> their code though no need to make code changes. We may need to mention that
> in the upgrade path if we want to keep it that way.
> 
> Guozhang
> 
> On Mon, Jun 5, 2017 at 2:28 PM, Jeyhun Karimov  wrote:
> 
>> Hi,
>>
>>
>> Sorry for late reply. Just to make everybody in sync, the current version
>> of KIP supports lambdas. "withKey" (ValueMapperWithKey) interfaces are
>> independent, meaning they do not extend from "withoutKey" (ValueMapper)
>> interfaces.
>>
>>
>> I agree with Guozhang, and I am personally a bit reluctant to increase
>> overloaded methods in public APIs but it seems this is only way to solve
>> all related jira issues.
>> However, the most overloaded methods will be with ValueJoiner type, which
>> will be with ValueJoinerWithKey with new overloaded methods. Other
>> interfaces require mostly 1 extra overload.
>>
>>
 I would suggest not doing it if user pop it up, but rather suggesting
>> them
 to use `map`
>>
>> I agree with Matthias as the core idea of this KIP was to collect all
>> related jira issues and propose one-shot solution for all. Afterwards, we
>> broke its scope into 2 KIPs (149 and 159).
>>
>> Cheers,
>> Jeyhun
>>
>>
>>
>> On Mon, Jun 5, 2017 at 7:55 AM Matthias J. Sax 
>> wrote:
>>
>>> I guess I missunderstood you. Your are right that overloading the method
>>> would also work. As both interfaces will be independent from each other,
>>> there should be no problem.
>>>
>>> The initial proposal was to use
>>>
 interface ValueMapperWithKey extends ValueMapper
>>>
>>> and this would break Lambda. We totally missed, that we don't need new
>>> methods but only only overlaods. Great you point this out! I was not
>>> quite happy with the newly added methods.
>>>
> I would suggest not doing it if user pop it up, but rather suggesting
>>> them
> to use `map`
>>>
>>> But this might introduce unnecessary re-partitioning for downstream
>>> operators. I don't thinks that a good suggestion. But if we only add new
>>> overloads for mapValue(), flatMapValue() etc, I don't see a big issue
>>> with "overstaffing" the API (what is btw a very valid concern).
>>>
>>>
>>> -Matthias
>>>
>>>
>>> On 6/4/17 10:37 PM, Guozhang Wang wrote:
 On Sun, Jun 4, 2017 at 8:41 PM, Matthias J. Sax >>
 wrote:

> We started with this proposal but it does not allow for Lambdas (in
>> case
> you want key access). Do you think preserving Lambdas is not important
> enough for this case -- I agree that there is some price to be paid to
> keep Lambdas.
>

 Not sure if I understand this comment.. My main point is not on
>> changing
 the proposal but just reduce it scope to `ValueJoinerWithKey` only; and
 even if we want to keep them all, I'd suggest we just implement the
>> added
 APIs by using the `KeyValueMapper` for `ValueMapperWithKeys`, etc,
>> which
 seems simpler to me. Does that affect lambda expression usage?

>
> About API consistency: I can't remember a concrete user request to
>> have
> key access in all operators. But I am pretty sure, if we only add it
>> for
> some, this request will pop up quickly. IMHO, it's better to do it all
> in one shot. (But I am not strict about it if most people think we
> should limit it to what was requested by users.)
>
>
 I would suggest not doing it if user pop it up, but rather suggesting
>>> them
 to use `map` etc directly but set the key unchanged rather than
>>> providing a
 new operator 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Guozhang Wang]

Jeyhun, Matthias:

Thanks for the explanation, I overlooked the repartition argument
previously.

1) Based on that argument I'm convinced of having ValueMapperWithKey /
ValueJoinerWithKey / ValueTransformerWithKey; though I'm still not
convinced with ReducerWithKey and InitializerWithKey since for the former
it can be covered with `aggregate` completely and with latter I have seen
little use cases with it.

2) Another comment is on public interface ValueTransformer extends
ValueTransformerCommon:

I think changing the interface to extend from a new interface is not binary
compatible though source compatible, i.e. users still need to recompile
their code though no need to make code changes. We may need to mention that
in the upgrade path if we want to keep it that way.

Guozhang

On Mon, Jun 5, 2017 at 2:28 PM, Jeyhun Karimov  wrote:

> Hi,
>
>
> Sorry for late reply. Just to make everybody in sync, the current version
> of KIP supports lambdas. "withKey" (ValueMapperWithKey) interfaces are
> independent, meaning they do not extend from "withoutKey" (ValueMapper)
> interfaces.
>
>
> I agree with Guozhang, and I am personally a bit reluctant to increase
> overloaded methods in public APIs but it seems this is only way to solve
> all related jira issues.
> However, the most overloaded methods will be with ValueJoiner type, which
> will be with ValueJoinerWithKey with new overloaded methods. Other
> interfaces require mostly 1 extra overload.
>
>
> >> I would suggest not doing it if user pop it up, but rather suggesting
> them
> >> to use `map`
>
> I agree with Matthias as the core idea of this KIP was to collect all
> related jira issues and propose one-shot solution for all. Afterwards, we
> broke its scope into 2 KIPs (149 and 159).
>
> Cheers,
> Jeyhun
>
>
>
> On Mon, Jun 5, 2017 at 7:55 AM Matthias J. Sax 
> wrote:
>
> > I guess I missunderstood you. Your are right that overloading the method
> > would also work. As both interfaces will be independent from each other,
> > there should be no problem.
> >
> > The initial proposal was to use
> >
> > > interface ValueMapperWithKey extends ValueMapper
> >
> > and this would break Lambda. We totally missed, that we don't need new
> > methods but only only overlaods. Great you point this out! I was not
> > quite happy with the newly added methods.
> >
> > >> I would suggest not doing it if user pop it up, but rather suggesting
> > them
> > >> to use `map`
> >
> > But this might introduce unnecessary re-partitioning for downstream
> > operators. I don't thinks that a good suggestion. But if we only add new
> > overloads for mapValue(), flatMapValue() etc, I don't see a big issue
> > with "overstaffing" the API (what is btw a very valid concern).
> >
> >
> > -Matthias
> >
> >
> > On 6/4/17 10:37 PM, Guozhang Wang wrote:
> > > On Sun, Jun 4, 2017 at 8:41 PM, Matthias J. Sax  >
> > > wrote:
> > >
> > >> We started with this proposal but it does not allow for Lambdas (in
> case
> > >> you want key access). Do you think preserving Lambdas is not important
> > >> enough for this case -- I agree that there is some price to be paid to
> > >> keep Lambdas.
> > >>
> > >
> > > Not sure if I understand this comment.. My main point is not on
> changing
> > > the proposal but just reduce it scope to `ValueJoinerWithKey` only; and
> > > even if we want to keep them all, I'd suggest we just implement the
> added
> > > APIs by using the `KeyValueMapper` for `ValueMapperWithKeys`, etc,
> which
> > > seems simpler to me. Does that affect lambda expression usage?
> > >
> > >>
> > >> About API consistency: I can't remember a concrete user request to
> have
> > >> key access in all operators. But I am pretty sure, if we only add it
> for
> > >> some, this request will pop up quickly. IMHO, it's better to do it all
> > >> in one shot. (But I am not strict about it if most people think we
> > >> should limit it to what was requested by users.)
> > >>
> > >>
> > > I would suggest not doing it if user pop it up, but rather suggesting
> > them
> > > to use `map` etc directly but set the key unchanged rather than
> > providing a
> > > new operator for it. To me some syntax sugars like this seems of less
> > > valuable than others (like print / writeAsText / foreach that are all
> > > depending on peek), and keeping adding them will just make the DSL too
> > > “overstaffed”.
> > >
> > >
> > >>
> > >> -Matthias
> > >>
> > >> On 6/4/17 6:23 PM, Guozhang Wang wrote:
> > >>> With KIP-159, the added "valueMapperWithKey" and
> > >> "valueTransformerWithKey"
> > >>> along seem to be just adding a few syntax-sugars? E.g. we can simply
> > >>> implement:
> > >>>
> > >>> mapValues(ValueMapperWithKey mapperWithKey)
> > >>>
> > >>> as
> > >>>
> > >>> map((k, v) -> (k, mapperWithKey(k, v))
> > >>>
> > >>> --
> > >>>
> > >>> I'm not sure how many users would really need such syntax sugars, and
> > >> even
> > 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

I guess I missunderstood you. Your are right that overloading the method
would also work. As both interfaces will be independent from each other,
there should be no problem.

The initial proposal was to use

> interface ValueMapperWithKey extends ValueMapper

and this would break Lambda. We totally missed, that we don't need new
methods but only only overlaods. Great you point this out! I was not
quite happy with the newly added methods.

>> I would suggest not doing it if user pop it up, but rather suggesting them
>> to use `map`

But this might introduce unnecessary re-partitioning for downstream
operators. I don't thinks that a good suggestion. But if we only add new
overloads for mapValue(), flatMapValue() etc, I don't see a big issue
with "overstaffing" the API (what is btw a very valid concern).


-Matthias


On 6/4/17 10:37 PM, Guozhang Wang wrote:
> On Sun, Jun 4, 2017 at 8:41 PM, Matthias J. Sax 
> wrote:
> 
>> We started with this proposal but it does not allow for Lambdas (in case
>> you want key access). Do you think preserving Lambdas is not important
>> enough for this case -- I agree that there is some price to be paid to
>> keep Lambdas.
>>
> 
> Not sure if I understand this comment.. My main point is not on changing
> the proposal but just reduce it scope to `ValueJoinerWithKey` only; and
> even if we want to keep them all, I'd suggest we just implement the added
> APIs by using the `KeyValueMapper` for `ValueMapperWithKeys`, etc, which
> seems simpler to me. Does that affect lambda expression usage?
> 
>>
>> About API consistency: I can't remember a concrete user request to have
>> key access in all operators. But I am pretty sure, if we only add it for
>> some, this request will pop up quickly. IMHO, it's better to do it all
>> in one shot. (But I am not strict about it if most people think we
>> should limit it to what was requested by users.)
>>
>>
> I would suggest not doing it if user pop it up, but rather suggesting them
> to use `map` etc directly but set the key unchanged rather than providing a
> new operator for it. To me some syntax sugars like this seems of less
> valuable than others (like print / writeAsText / foreach that are all
> depending on peek), and keeping adding them will just make the DSL too
> “overstaffed”.
> 
> 
>>
>> -Matthias
>>
>> On 6/4/17 6:23 PM, Guozhang Wang wrote:
>>> With KIP-159, the added "valueMapperWithKey" and
>> "valueTransformerWithKey"
>>> along seem to be just adding a few syntax-sugars? E.g. we can simply
>>> implement:
>>>
>>> mapValues(ValueMapperWithKey mapperWithKey)
>>>
>>> as
>>>
>>> map((k, v) -> (k, mapperWithKey(k, v))
>>>
>>> --
>>>
>>> I'm not sure how many users would really need such syntax sugars, and
>> even
>>> they do, we can support them easily as the above implementations;
>>>
>>> Similarly for "ReducerWithKey", it can be implemented as `Aggregator> V,
>>> V>`, and people who needs key access can just use `aggregate` directly.
>>>
>>> The function which I think is really of valuable is `ValueJoinerWithKey`,
>>> and that seems to be the original request from users while others are
>>> coming from "API consistency" concerns. Personally I'd prefer only keep
>> the
>>> last one (`InitializerWithKey` might also have some value, but I have not
>>> seen people widely requesting it in their DSL usage yet; if there is a
>>> common request we can keep it in this KIP as well). WDYT?
>>>
>>> Guozhang
>>>
>>>
>>> On Sun, May 28, 2017 at 10:16 AM, Jeyhun Karimov 
>>> wrote:
>>>
 Thanks for clarification Matthias, now everything is clear.

 On Sun, May 28, 2017 at 6:21 PM Matthias J. Sax 
 wrote:

> I don't think we can drop ValueTransformerSupplier. If you don't have
>> an
> supplier, you only get a single instance of your function. But for a
> stateful transformation, we need multiple instances (one for each task)
> of ValueTransformer.
>
> We don't need suppliers for functions like "ValueMapper" etc because
> those are stateless and thus, we can reuse a single instance over
> multiple tasks -- but we can't do this for ValueTransformer (and
 similar).
>
> Btw: This reminds me about KIP-159: with regard to the RichFunction we
> might need a supplier pattern, too. (I'll comment on the other thread,
> too.)
>
>
> -Matthias
>
> On 5/28/17 5:45 AM, Jeyhun Karimov wrote:
>> Hi,
>>
>> I updated KIP.
>> Just to avoid misunderstanding, I meant deprecating
> ValueTransformerSupplier
>> and I am ok with ValueTransformer.
>> So instead of using ValueTransformerSupplier can't we directly use
>> ValueTransformer
>> or ValueTransformerWithKey?
>>
>> Btw, in current design all features of ValueTransformer will be
 available
>> in  ValueTransformerWithKey interface.
>>
>> Cheers,
>> Jeyhun
>>
>> On 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Guozhang Wang]

On Sun, Jun 4, 2017 at 8:41 PM, Matthias J. Sax 
wrote:

> We started with this proposal but it does not allow for Lambdas (in case
> you want key access). Do you think preserving Lambdas is not important
> enough for this case -- I agree that there is some price to be paid to
> keep Lambdas.
>

Not sure if I understand this comment.. My main point is not on changing
the proposal but just reduce it scope to `ValueJoinerWithKey` only; and
even if we want to keep them all, I'd suggest we just implement the added
APIs by using the `KeyValueMapper` for `ValueMapperWithKeys`, etc, which
seems simpler to me. Does that affect lambda expression usage?

>
> About API consistency: I can't remember a concrete user request to have
> key access in all operators. But I am pretty sure, if we only add it for
> some, this request will pop up quickly. IMHO, it's better to do it all
> in one shot. (But I am not strict about it if most people think we
> should limit it to what was requested by users.)
>
>
I would suggest not doing it if user pop it up, but rather suggesting them
to use `map` etc directly but set the key unchanged rather than providing a
new operator for it. To me some syntax sugars like this seems of less
valuable than others (like print / writeAsText / foreach that are all
depending on peek), and keeping adding them will just make the DSL too
“overstaffed”.


>
> -Matthias
>
> On 6/4/17 6:23 PM, Guozhang Wang wrote:
> > With KIP-159, the added "valueMapperWithKey" and
> "valueTransformerWithKey"
> > along seem to be just adding a few syntax-sugars? E.g. we can simply
> > implement:
> >
> > mapValues(ValueMapperWithKey mapperWithKey)
> >
> > as
> >
> > map((k, v) -> (k, mapperWithKey(k, v))
> >
> > --
> >
> > I'm not sure how many users would really need such syntax sugars, and
> even
> > they do, we can support them easily as the above implementations;
> >
> > Similarly for "ReducerWithKey", it can be implemented as `Aggregator V,
> > V>`, and people who needs key access can just use `aggregate` directly.
> >
> > The function which I think is really of valuable is `ValueJoinerWithKey`,
> > and that seems to be the original request from users while others are
> > coming from "API consistency" concerns. Personally I'd prefer only keep
> the
> > last one (`InitializerWithKey` might also have some value, but I have not
> > seen people widely requesting it in their DSL usage yet; if there is a
> > common request we can keep it in this KIP as well). WDYT?
> >
> > Guozhang
> >
> >
> > On Sun, May 28, 2017 at 10:16 AM, Jeyhun Karimov 
> > wrote:
> >
> >> Thanks for clarification Matthias, now everything is clear.
> >>
> >> On Sun, May 28, 2017 at 6:21 PM Matthias J. Sax 
> >> wrote:
> >>
> >>> I don't think we can drop ValueTransformerSupplier. If you don't have
> an
> >>> supplier, you only get a single instance of your function. But for a
> >>> stateful transformation, we need multiple instances (one for each task)
> >>> of ValueTransformer.
> >>>
> >>> We don't need suppliers for functions like "ValueMapper" etc because
> >>> those are stateless and thus, we can reuse a single instance over
> >>> multiple tasks -- but we can't do this for ValueTransformer (and
> >> similar).
> >>>
> >>> Btw: This reminds me about KIP-159: with regard to the RichFunction we
> >>> might need a supplier pattern, too. (I'll comment on the other thread,
> >>> too.)
> >>>
> >>>
> >>> -Matthias
> >>>
> >>> On 5/28/17 5:45 AM, Jeyhun Karimov wrote:
>  Hi,
> 
>  I updated KIP.
>  Just to avoid misunderstanding, I meant deprecating
> >>> ValueTransformerSupplier
>  and I am ok with ValueTransformer.
>  So instead of using ValueTransformerSupplier can't we directly use
>  ValueTransformer
>  or ValueTransformerWithKey?
> 
>  Btw, in current design all features of ValueTransformer will be
> >> available
>  in  ValueTransformerWithKey interface.
> 
>  Cheers,
>  Jeyhun
> 
>  On Sun, May 28, 2017 at 6:15 AM Matthias J. Sax <
> matth...@confluent.io
> >>>
>  wrote:
> 
> > Thanks Jeyhun.
> >
> > About ValueTransformer: I don't think we can remove it. Note,
> > ValueTransformer allows to attach a state and also allows to register
> > punctuations. Both those features will not be available via withKey()
> > interfaces.
> >
> > -Matthias
> >
> >
> > On 5/27/17 1:25 PM, Jeyhun Karimov wrote:
> >> Hi Matthias,
> >>
> >> Thanks for your comments.
> >>
> >> I tested the deep copy approach. It has significant overhead.
> >>> Especially
> >> for "light" and stateless operators it slows down the topology
> >> significantly (> 20% ). I think "warning"  users about not-changing
> >> the
> > key
> >> is better warning them about possible performance loss.
> >>
> >> About the interfaces, additionally I 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

We started with this proposal but it does not allow for Lambdas (in case
you want key access). Do you think preserving Lambdas is not important
enough for this case -- I agree that there is some price to be paid to
keep Lambdas.

About API consistency: I can't remember a concrete user request to have
key access in all operators. But I am pretty sure, if we only add it for
some, this request will pop up quickly. IMHO, it's better to do it all
in one shot. (But I am not strict about it if most people think we
should limit it to what was requested by users.)


-Matthias

On 6/4/17 6:23 PM, Guozhang Wang wrote:
> With KIP-159, the added "valueMapperWithKey" and "valueTransformerWithKey"
> along seem to be just adding a few syntax-sugars? E.g. we can simply
> implement:
> 
> mapValues(ValueMapperWithKey mapperWithKey)
> 
> as
> 
> map((k, v) -> (k, mapperWithKey(k, v))
> 
> --
> 
> I'm not sure how many users would really need such syntax sugars, and even
> they do, we can support them easily as the above implementations;
> 
> Similarly for "ReducerWithKey", it can be implemented as `Aggregator V>`, and people who needs key access can just use `aggregate` directly.
> 
> The function which I think is really of valuable is `ValueJoinerWithKey`,
> and that seems to be the original request from users while others are
> coming from "API consistency" concerns. Personally I'd prefer only keep the
> last one (`InitializerWithKey` might also have some value, but I have not
> seen people widely requesting it in their DSL usage yet; if there is a
> common request we can keep it in this KIP as well). WDYT?
> 
> Guozhang
> 
> 
> On Sun, May 28, 2017 at 10:16 AM, Jeyhun Karimov 
> wrote:
> 
>> Thanks for clarification Matthias, now everything is clear.
>>
>> On Sun, May 28, 2017 at 6:21 PM Matthias J. Sax 
>> wrote:
>>
>>> I don't think we can drop ValueTransformerSupplier. If you don't have an
>>> supplier, you only get a single instance of your function. But for a
>>> stateful transformation, we need multiple instances (one for each task)
>>> of ValueTransformer.
>>>
>>> We don't need suppliers for functions like "ValueMapper" etc because
>>> those are stateless and thus, we can reuse a single instance over
>>> multiple tasks -- but we can't do this for ValueTransformer (and
>> similar).
>>>
>>> Btw: This reminds me about KIP-159: with regard to the RichFunction we
>>> might need a supplier pattern, too. (I'll comment on the other thread,
>>> too.)
>>>
>>>
>>> -Matthias
>>>
>>> On 5/28/17 5:45 AM, Jeyhun Karimov wrote:
 Hi,

 I updated KIP.
 Just to avoid misunderstanding, I meant deprecating
>>> ValueTransformerSupplier
 and I am ok with ValueTransformer.
 So instead of using ValueTransformerSupplier can't we directly use
 ValueTransformer
 or ValueTransformerWithKey?

 Btw, in current design all features of ValueTransformer will be
>> available
 in  ValueTransformerWithKey interface.

 Cheers,
 Jeyhun

 On Sun, May 28, 2017 at 6:15 AM Matthias J. Sax >>
 wrote:

> Thanks Jeyhun.
>
> About ValueTransformer: I don't think we can remove it. Note,
> ValueTransformer allows to attach a state and also allows to register
> punctuations. Both those features will not be available via withKey()
> interfaces.
>
> -Matthias
>
>
> On 5/27/17 1:25 PM, Jeyhun Karimov wrote:
>> Hi Matthias,
>>
>> Thanks for your comments.
>>
>> I tested the deep copy approach. It has significant overhead.
>>> Especially
>> for "light" and stateless operators it slows down the topology
>> significantly (> 20% ). I think "warning"  users about not-changing
>> the
> key
>> is better warning them about possible performance loss.
>>
>> About the interfaces, additionally I considered adding
> InitializerWithKey,
>> AggregatorWithKey and ValueTransformerWithKey. I think they are
>>> included
> in
>> PR but not in KIP. I will also include them in KIP, sorry my bad.
>> Including ReducerWithKey definitely makes sense. Thanks.
>>
>> One thing I want to mention is that, maybe we should deprecate
>> methods
> with
>> argument type ValueTransformerSupplier (KStream.transformValues(...))
>>> and
>> and as a whole the ValueTransformerSupplier interface.
>> We can use ValueTransformer/ValueTransformerWithKey type instead
>>> without
>> additional supplier layer.
>>
>>
>> Cheers,
>> Jeyhun
>>
>>
>> On Thu, May 25, 2017 at 1:07 AM Matthias J. Sax <
>> matth...@confluent.io

>> wrote:
>>
>>> One more question:
>>>
>>> Should we add any of
>>>  - InitizialierWithKey
>>>  - ReducerWithKey
>>>  - ValueTransformerWithKey
>>>
>>> To get consistent/complete API, it might be a good idea. Any
>> thoughts?

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Guozhang Wang]

With KIP-159, the added "valueMapperWithKey" and "valueTransformerWithKey"
along seem to be just adding a few syntax-sugars? E.g. we can simply
implement:

mapValues(ValueMapperWithKey mapperWithKey)

as

map((k, v) -> (k, mapperWithKey(k, v))

--

I'm not sure how many users would really need such syntax sugars, and even
they do, we can support them easily as the above implementations;

Similarly for "ReducerWithKey", it can be implemented as `Aggregator`, and people who needs key access can just use `aggregate` directly.

The function which I think is really of valuable is `ValueJoinerWithKey`,
and that seems to be the original request from users while others are
coming from "API consistency" concerns. Personally I'd prefer only keep the
last one (`InitializerWithKey` might also have some value, but I have not
seen people widely requesting it in their DSL usage yet; if there is a
common request we can keep it in this KIP as well). WDYT?

Guozhang


On Sun, May 28, 2017 at 10:16 AM, Jeyhun Karimov 
wrote:

> Thanks for clarification Matthias, now everything is clear.
>
> On Sun, May 28, 2017 at 6:21 PM Matthias J. Sax 
> wrote:
>
> > I don't think we can drop ValueTransformerSupplier. If you don't have an
> > supplier, you only get a single instance of your function. But for a
> > stateful transformation, we need multiple instances (one for each task)
> > of ValueTransformer.
> >
> > We don't need suppliers for functions like "ValueMapper" etc because
> > those are stateless and thus, we can reuse a single instance over
> > multiple tasks -- but we can't do this for ValueTransformer (and
> similar).
> >
> > Btw: This reminds me about KIP-159: with regard to the RichFunction we
> > might need a supplier pattern, too. (I'll comment on the other thread,
> > too.)
> >
> >
> > -Matthias
> >
> > On 5/28/17 5:45 AM, Jeyhun Karimov wrote:
> > > Hi,
> > >
> > > I updated KIP.
> > > Just to avoid misunderstanding, I meant deprecating
> > ValueTransformerSupplier
> > > and I am ok with ValueTransformer.
> > > So instead of using ValueTransformerSupplier can't we directly use
> > > ValueTransformer
> > > or ValueTransformerWithKey?
> > >
> > > Btw, in current design all features of ValueTransformer will be
> available
> > > in  ValueTransformerWithKey interface.
> > >
> > > Cheers,
> > > Jeyhun
> > >
> > > On Sun, May 28, 2017 at 6:15 AM Matthias J. Sax  >
> > > wrote:
> > >
> > >> Thanks Jeyhun.
> > >>
> > >> About ValueTransformer: I don't think we can remove it. Note,
> > >> ValueTransformer allows to attach a state and also allows to register
> > >> punctuations. Both those features will not be available via withKey()
> > >> interfaces.
> > >>
> > >> -Matthias
> > >>
> > >>
> > >> On 5/27/17 1:25 PM, Jeyhun Karimov wrote:
> > >>> Hi Matthias,
> > >>>
> > >>> Thanks for your comments.
> > >>>
> > >>> I tested the deep copy approach. It has significant overhead.
> > Especially
> > >>> for "light" and stateless operators it slows down the topology
> > >>> significantly (> 20% ). I think "warning"  users about not-changing
> the
> > >> key
> > >>> is better warning them about possible performance loss.
> > >>>
> > >>> About the interfaces, additionally I considered adding
> > >> InitializerWithKey,
> > >>> AggregatorWithKey and ValueTransformerWithKey. I think they are
> > included
> > >> in
> > >>> PR but not in KIP. I will also include them in KIP, sorry my bad.
> > >>> Including ReducerWithKey definitely makes sense. Thanks.
> > >>>
> > >>> One thing I want to mention is that, maybe we should deprecate
> methods
> > >> with
> > >>> argument type ValueTransformerSupplier (KStream.transformValues(...))
> > and
> > >>> and as a whole the ValueTransformerSupplier interface.
> > >>> We can use ValueTransformer/ValueTransformerWithKey type instead
> > without
> > >>> additional supplier layer.
> > >>>
> > >>>
> > >>> Cheers,
> > >>> Jeyhun
> > >>>
> > >>>
> > >>> On Thu, May 25, 2017 at 1:07 AM Matthias J. Sax <
> matth...@confluent.io
> > >
> > >>> wrote:
> > >>>
> >  One more question:
> > 
> >  Should we add any of
> >   - InitizialierWithKey
> >   - ReducerWithKey
> >   - ValueTransformerWithKey
> > 
> >  To get consistent/complete API, it might be a good idea. Any
> thoughts?
> > 
> > 
> >  -Matthias
> > 
> > 
> >  On 5/24/17 3:47 PM, Matthias J. Sax wrote:
> > > Jeyhun,
> > >
> > > I was just wondering if you did look into the key-deep-copy idea we
> > > discussed. I am curious to see what the impact might be.
> > >
> > >
> > > -Matthias
> > >
> > > On 5/20/17 2:03 AM, Jeyhun Karimov wrote:
> > >> Hi,
> > >>
> > >> Thanks for your comments. I rethink about including rich functions
> > >> into
> > >> this KIP.
> > >> I think once we include rich functions in this KIP and then fix
> > >> ProcessorContext 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Thanks for clarification Matthias, now everything is clear.

On Sun, May 28, 2017 at 6:21 PM Matthias J. Sax 
wrote:

> I don't think we can drop ValueTransformerSupplier. If you don't have an
> supplier, you only get a single instance of your function. But for a
> stateful transformation, we need multiple instances (one for each task)
> of ValueTransformer.
>
> We don't need suppliers for functions like "ValueMapper" etc because
> those are stateless and thus, we can reuse a single instance over
> multiple tasks -- but we can't do this for ValueTransformer (and similar).
>
> Btw: This reminds me about KIP-159: with regard to the RichFunction we
> might need a supplier pattern, too. (I'll comment on the other thread,
> too.)
>
>
> -Matthias
>
> On 5/28/17 5:45 AM, Jeyhun Karimov wrote:
> > Hi,
> >
> > I updated KIP.
> > Just to avoid misunderstanding, I meant deprecating
> ValueTransformerSupplier
> > and I am ok with ValueTransformer.
> > So instead of using ValueTransformerSupplier can't we directly use
> > ValueTransformer
> > or ValueTransformerWithKey?
> >
> > Btw, in current design all features of ValueTransformer will be available
> > in  ValueTransformerWithKey interface.
> >
> > Cheers,
> > Jeyhun
> >
> > On Sun, May 28, 2017 at 6:15 AM Matthias J. Sax 
> > wrote:
> >
> >> Thanks Jeyhun.
> >>
> >> About ValueTransformer: I don't think we can remove it. Note,
> >> ValueTransformer allows to attach a state and also allows to register
> >> punctuations. Both those features will not be available via withKey()
> >> interfaces.
> >>
> >> -Matthias
> >>
> >>
> >> On 5/27/17 1:25 PM, Jeyhun Karimov wrote:
> >>> Hi Matthias,
> >>>
> >>> Thanks for your comments.
> >>>
> >>> I tested the deep copy approach. It has significant overhead.
> Especially
> >>> for "light" and stateless operators it slows down the topology
> >>> significantly (> 20% ). I think "warning"  users about not-changing the
> >> key
> >>> is better warning them about possible performance loss.
> >>>
> >>> About the interfaces, additionally I considered adding
> >> InitializerWithKey,
> >>> AggregatorWithKey and ValueTransformerWithKey. I think they are
> included
> >> in
> >>> PR but not in KIP. I will also include them in KIP, sorry my bad.
> >>> Including ReducerWithKey definitely makes sense. Thanks.
> >>>
> >>> One thing I want to mention is that, maybe we should deprecate methods
> >> with
> >>> argument type ValueTransformerSupplier (KStream.transformValues(...))
> and
> >>> and as a whole the ValueTransformerSupplier interface.
> >>> We can use ValueTransformer/ValueTransformerWithKey type instead
> without
> >>> additional supplier layer.
> >>>
> >>>
> >>> Cheers,
> >>> Jeyhun
> >>>
> >>>
> >>> On Thu, May 25, 2017 at 1:07 AM Matthias J. Sax  >
> >>> wrote:
> >>>
>  One more question:
> 
>  Should we add any of
>   - InitizialierWithKey
>   - ReducerWithKey
>   - ValueTransformerWithKey
> 
>  To get consistent/complete API, it might be a good idea. Any thoughts?
> 
> 
>  -Matthias
> 
> 
>  On 5/24/17 3:47 PM, Matthias J. Sax wrote:
> > Jeyhun,
> >
> > I was just wondering if you did look into the key-deep-copy idea we
> > discussed. I am curious to see what the impact might be.
> >
> >
> > -Matthias
> >
> > On 5/20/17 2:03 AM, Jeyhun Karimov wrote:
> >> Hi,
> >>
> >> Thanks for your comments. I rethink about including rich functions
> >> into
> >> this KIP.
> >> I think once we include rich functions in this KIP and then fix
> >> ProcessorContext in another KIP and incorporate with existing rich
> >> functions, the code will not be backwards compatible.
> >>
> >> I see Damian's and your point more clearly now.
> >>
> >> Conclusion: we include only withKey interfaces in this KIP (I
> updated
>  the
> >> KIP), I will try also initiate another KIP for rich functions.
> >>
> >> Cheers,
> >> Jeyhun
> >>
> >> On Fri, May 19, 2017 at 10:50 PM Matthias J. Sax <
> >> matth...@confluent.io
> >
> >> wrote:
> >>
> >>> With the current KIP, using ValueMapper and ValueMapperWithKey
> >>> interfaces, RichFunction seems to be an independent add-on. To fix
> >> the
> >>> original issue to allow key access, RichFunctions are not required
>  IMHO.
> >>>
> >>> I initially put the RichFunction idea on the table, because I was
>  hoping
> >>> to get a uniform API. And I think, is was good to consider them --
> >>> however, the discussion showed that they are not necessary for key
> >>> access. Thus, it seems to be better to handle RichFunctions in an
> own
> >>> KIP. The ProcessorContext/RecordContext issues seems to be a main
> >>> challenge for this. And introducing RichFunctions with
> parameter-less
> >>> init() method, seem not to help too much. We would 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

I don't think we can drop ValueTransformerSupplier. If you don't have an
supplier, you only get a single instance of your function. But for a
stateful transformation, we need multiple instances (one for each task)
of ValueTransformer.

We don't need suppliers for functions like "ValueMapper" etc because
those are stateless and thus, we can reuse a single instance over
multiple tasks -- but we can't do this for ValueTransformer (and similar).

Btw: This reminds me about KIP-159: with regard to the RichFunction we
might need a supplier pattern, too. (I'll comment on the other thread, too.)


-Matthias

On 5/28/17 5:45 AM, Jeyhun Karimov wrote:
> Hi,
> 
> I updated KIP.
> Just to avoid misunderstanding, I meant deprecating  ValueTransformerSupplier
> and I am ok with ValueTransformer.
> So instead of using ValueTransformerSupplier can't we directly use
> ValueTransformer
> or ValueTransformerWithKey?
> 
> Btw, in current design all features of ValueTransformer will be available
> in  ValueTransformerWithKey interface.
> 
> Cheers,
> Jeyhun
> 
> On Sun, May 28, 2017 at 6:15 AM Matthias J. Sax 
> wrote:
> 
>> Thanks Jeyhun.
>>
>> About ValueTransformer: I don't think we can remove it. Note,
>> ValueTransformer allows to attach a state and also allows to register
>> punctuations. Both those features will not be available via withKey()
>> interfaces.
>>
>> -Matthias
>>
>>
>> On 5/27/17 1:25 PM, Jeyhun Karimov wrote:
>>> Hi Matthias,
>>>
>>> Thanks for your comments.
>>>
>>> I tested the deep copy approach. It has significant overhead. Especially
>>> for "light" and stateless operators it slows down the topology
>>> significantly (> 20% ). I think "warning"  users about not-changing the
>> key
>>> is better warning them about possible performance loss.
>>>
>>> About the interfaces, additionally I considered adding
>> InitializerWithKey,
>>> AggregatorWithKey and ValueTransformerWithKey. I think they are included
>> in
>>> PR but not in KIP. I will also include them in KIP, sorry my bad.
>>> Including ReducerWithKey definitely makes sense. Thanks.
>>>
>>> One thing I want to mention is that, maybe we should deprecate methods
>> with
>>> argument type ValueTransformerSupplier (KStream.transformValues(...)) and
>>> and as a whole the ValueTransformerSupplier interface.
>>> We can use ValueTransformer/ValueTransformerWithKey type instead without
>>> additional supplier layer.
>>>
>>>
>>> Cheers,
>>> Jeyhun
>>>
>>>
>>> On Thu, May 25, 2017 at 1:07 AM Matthias J. Sax 
>>> wrote:
>>>
 One more question:

 Should we add any of
  - InitizialierWithKey
  - ReducerWithKey
  - ValueTransformerWithKey

 To get consistent/complete API, it might be a good idea. Any thoughts?


 -Matthias


 On 5/24/17 3:47 PM, Matthias J. Sax wrote:
> Jeyhun,
>
> I was just wondering if you did look into the key-deep-copy idea we
> discussed. I am curious to see what the impact might be.
>
>
> -Matthias
>
> On 5/20/17 2:03 AM, Jeyhun Karimov wrote:
>> Hi,
>>
>> Thanks for your comments. I rethink about including rich functions
>> into
>> this KIP.
>> I think once we include rich functions in this KIP and then fix
>> ProcessorContext in another KIP and incorporate with existing rich
>> functions, the code will not be backwards compatible.
>>
>> I see Damian's and your point more clearly now.
>>
>> Conclusion: we include only withKey interfaces in this KIP (I updated
 the
>> KIP), I will try also initiate another KIP for rich functions.
>>
>> Cheers,
>> Jeyhun
>>
>> On Fri, May 19, 2017 at 10:50 PM Matthias J. Sax <
>> matth...@confluent.io
>
>> wrote:
>>
>>> With the current KIP, using ValueMapper and ValueMapperWithKey
>>> interfaces, RichFunction seems to be an independent add-on. To fix
>> the
>>> original issue to allow key access, RichFunctions are not required
 IMHO.
>>>
>>> I initially put the RichFunction idea on the table, because I was
 hoping
>>> to get a uniform API. And I think, is was good to consider them --
>>> however, the discussion showed that they are not necessary for key
>>> access. Thus, it seems to be better to handle RichFunctions in an own
>>> KIP. The ProcessorContext/RecordContext issues seems to be a main
>>> challenge for this. And introducing RichFunctions with parameter-less
>>> init() method, seem not to help too much. We would get an
 "intermediate"
>>> API that we want to change anyway later on...
>>>
>>> As you put already much effort into RichFunction, feel free do push
 this
>>> further and start a new KIP (we can do this even in parallel) -- we
>>> don't want to slow you down :) But it make the discussion and code
>>> review easier, if we separate both IMHO.
>>>
>>>
>>> -Matthias
>>>
>>>

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi,

I updated KIP.
Just to avoid misunderstanding, I meant deprecating  ValueTransformerSupplier
and I am ok with ValueTransformer.
So instead of using ValueTransformerSupplier can't we directly use
ValueTransformer
or ValueTransformerWithKey?

Btw, in current design all features of ValueTransformer will be available
in  ValueTransformerWithKey interface.

Cheers,
Jeyhun

On Sun, May 28, 2017 at 6:15 AM Matthias J. Sax 
wrote:

> Thanks Jeyhun.
>
> About ValueTransformer: I don't think we can remove it. Note,
> ValueTransformer allows to attach a state and also allows to register
> punctuations. Both those features will not be available via withKey()
> interfaces.
>
> -Matthias
>
>
> On 5/27/17 1:25 PM, Jeyhun Karimov wrote:
> > Hi Matthias,
> >
> > Thanks for your comments.
> >
> > I tested the deep copy approach. It has significant overhead. Especially
> > for "light" and stateless operators it slows down the topology
> > significantly (> 20% ). I think "warning"  users about not-changing the
> key
> > is better warning them about possible performance loss.
> >
> > About the interfaces, additionally I considered adding
> InitializerWithKey,
> > AggregatorWithKey and ValueTransformerWithKey. I think they are included
> in
> > PR but not in KIP. I will also include them in KIP, sorry my bad.
> > Including ReducerWithKey definitely makes sense. Thanks.
> >
> > One thing I want to mention is that, maybe we should deprecate methods
> with
> > argument type ValueTransformerSupplier (KStream.transformValues(...)) and
> > and as a whole the ValueTransformerSupplier interface.
> > We can use ValueTransformer/ValueTransformerWithKey type instead without
> > additional supplier layer.
> >
> >
> > Cheers,
> > Jeyhun
> >
> >
> > On Thu, May 25, 2017 at 1:07 AM Matthias J. Sax 
> > wrote:
> >
> >> One more question:
> >>
> >> Should we add any of
> >>  - InitizialierWithKey
> >>  - ReducerWithKey
> >>  - ValueTransformerWithKey
> >>
> >> To get consistent/complete API, it might be a good idea. Any thoughts?
> >>
> >>
> >> -Matthias
> >>
> >>
> >> On 5/24/17 3:47 PM, Matthias J. Sax wrote:
> >>> Jeyhun,
> >>>
> >>> I was just wondering if you did look into the key-deep-copy idea we
> >>> discussed. I am curious to see what the impact might be.
> >>>
> >>>
> >>> -Matthias
> >>>
> >>> On 5/20/17 2:03 AM, Jeyhun Karimov wrote:
>  Hi,
> 
>  Thanks for your comments. I rethink about including rich functions
> into
>  this KIP.
>  I think once we include rich functions in this KIP and then fix
>  ProcessorContext in another KIP and incorporate with existing rich
>  functions, the code will not be backwards compatible.
> 
>  I see Damian's and your point more clearly now.
> 
>  Conclusion: we include only withKey interfaces in this KIP (I updated
> >> the
>  KIP), I will try also initiate another KIP for rich functions.
> 
>  Cheers,
>  Jeyhun
> 
>  On Fri, May 19, 2017 at 10:50 PM Matthias J. Sax <
> matth...@confluent.io
> >>>
>  wrote:
> 
> > With the current KIP, using ValueMapper and ValueMapperWithKey
> > interfaces, RichFunction seems to be an independent add-on. To fix
> the
> > original issue to allow key access, RichFunctions are not required
> >> IMHO.
> >
> > I initially put the RichFunction idea on the table, because I was
> >> hoping
> > to get a uniform API. And I think, is was good to consider them --
> > however, the discussion showed that they are not necessary for key
> > access. Thus, it seems to be better to handle RichFunctions in an own
> > KIP. The ProcessorContext/RecordContext issues seems to be a main
> > challenge for this. And introducing RichFunctions with parameter-less
> > init() method, seem not to help too much. We would get an
> >> "intermediate"
> > API that we want to change anyway later on...
> >
> > As you put already much effort into RichFunction, feel free do push
> >> this
> > further and start a new KIP (we can do this even in parallel) -- we
> > don't want to slow you down :) But it make the discussion and code
> > review easier, if we separate both IMHO.
> >
> >
> > -Matthias
> >
> >
> > On 5/19/17 2:25 AM, Jeyhun Karimov wrote:
> >> Hi Damian,
> >>
> >> Thanks for your comments. I think providing to users *interface*
> >> rather
> >> than *abstract class* should be preferred (Matthias also raised this
> > issue
> >> ), anyway I changed the corresponding parts of KIP.
> >>
> >> Regarding with passing additional contextual information, I think it
> >> is a
> >> tradeoff,
> >> 1) first, we fix the context parameter for *init() *method in
> another
> >> PR
> >> and solve Rich functions afterwards
> >> 2) first, we fix the requested issues on jira ([1-3]) with providing
> >> (not-complete) Rich functions and integrate the 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Thanks Jeyhun.

About ValueTransformer: I don't think we can remove it. Note,
ValueTransformer allows to attach a state and also allows to register
punctuations. Both those features will not be available via withKey()
interfaces.

-Matthias


On 5/27/17 1:25 PM, Jeyhun Karimov wrote:
> Hi Matthias,
> 
> Thanks for your comments.
> 
> I tested the deep copy approach. It has significant overhead. Especially
> for "light" and stateless operators it slows down the topology
> significantly (> 20% ). I think "warning"  users about not-changing the key
> is better warning them about possible performance loss.
> 
> About the interfaces, additionally I considered adding InitializerWithKey,
> AggregatorWithKey and ValueTransformerWithKey. I think they are included in
> PR but not in KIP. I will also include them in KIP, sorry my bad.
> Including ReducerWithKey definitely makes sense. Thanks.
> 
> One thing I want to mention is that, maybe we should deprecate methods with
> argument type ValueTransformerSupplier (KStream.transformValues(...)) and
> and as a whole the ValueTransformerSupplier interface.
> We can use ValueTransformer/ValueTransformerWithKey type instead without
> additional supplier layer.
> 
> 
> Cheers,
> Jeyhun
> 
> 
> On Thu, May 25, 2017 at 1:07 AM Matthias J. Sax 
> wrote:
> 
>> One more question:
>>
>> Should we add any of
>>  - InitizialierWithKey
>>  - ReducerWithKey
>>  - ValueTransformerWithKey
>>
>> To get consistent/complete API, it might be a good idea. Any thoughts?
>>
>>
>> -Matthias
>>
>>
>> On 5/24/17 3:47 PM, Matthias J. Sax wrote:
>>> Jeyhun,
>>>
>>> I was just wondering if you did look into the key-deep-copy idea we
>>> discussed. I am curious to see what the impact might be.
>>>
>>>
>>> -Matthias
>>>
>>> On 5/20/17 2:03 AM, Jeyhun Karimov wrote:
 Hi,

 Thanks for your comments. I rethink about including rich functions into
 this KIP.
 I think once we include rich functions in this KIP and then fix
 ProcessorContext in another KIP and incorporate with existing rich
 functions, the code will not be backwards compatible.

 I see Damian's and your point more clearly now.

 Conclusion: we include only withKey interfaces in this KIP (I updated
>> the
 KIP), I will try also initiate another KIP for rich functions.

 Cheers,
 Jeyhun

 On Fri, May 19, 2017 at 10:50 PM Matthias J. Sax >>
 wrote:

> With the current KIP, using ValueMapper and ValueMapperWithKey
> interfaces, RichFunction seems to be an independent add-on. To fix the
> original issue to allow key access, RichFunctions are not required
>> IMHO.
>
> I initially put the RichFunction idea on the table, because I was
>> hoping
> to get a uniform API. And I think, is was good to consider them --
> however, the discussion showed that they are not necessary for key
> access. Thus, it seems to be better to handle RichFunctions in an own
> KIP. The ProcessorContext/RecordContext issues seems to be a main
> challenge for this. And introducing RichFunctions with parameter-less
> init() method, seem not to help too much. We would get an
>> "intermediate"
> API that we want to change anyway later on...
>
> As you put already much effort into RichFunction, feel free do push
>> this
> further and start a new KIP (we can do this even in parallel) -- we
> don't want to slow you down :) But it make the discussion and code
> review easier, if we separate both IMHO.
>
>
> -Matthias
>
>
> On 5/19/17 2:25 AM, Jeyhun Karimov wrote:
>> Hi Damian,
>>
>> Thanks for your comments. I think providing to users *interface*
>> rather
>> than *abstract class* should be preferred (Matthias also raised this
> issue
>> ), anyway I changed the corresponding parts of KIP.
>>
>> Regarding with passing additional contextual information, I think it
>> is a
>> tradeoff,
>> 1) first, we fix the context parameter for *init() *method in another
>> PR
>> and solve Rich functions afterwards
>> 2) first, we fix the requested issues on jira ([1-3]) with providing
>> (not-complete) Rich functions and integrate the context parameters to
> this
>> afterwards (like improvement)
>>
>> To me, the second approach seems more incremental. However you are
>> right,
>> the names might confuse the users.
>>
>>
>>
>> [1] https://issues.apache.org/jira/browse/KAFKA-4218
>> [2] https://issues.apache.org/jira/browse/KAFKA-4726
>> [3] https://issues.apache.org/jira/browse/KAFKA-3745
>>
>>
>> Cheers,
>> Jeyhun
>>
>>
>> On Fri, May 19, 2017 at 10:42 AM Damian Guy 
> wrote:
>>
>>> Hi,
>>>
>>> I see you've removed the `ProcessorContext` from the RichFunction
>> which
> is
>>> good, but why is it a `RichFunction`? 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi Matthias,

Thanks for your comments.

I tested the deep copy approach. It has significant overhead. Especially
for "light" and stateless operators it slows down the topology
significantly (> 20% ). I think "warning"  users about not-changing the key
is better warning them about possible performance loss.

About the interfaces, additionally I considered adding InitializerWithKey,
AggregatorWithKey and ValueTransformerWithKey. I think they are included in
PR but not in KIP. I will also include them in KIP, sorry my bad.
Including ReducerWithKey definitely makes sense. Thanks.

One thing I want to mention is that, maybe we should deprecate methods with
argument type ValueTransformerSupplier (KStream.transformValues(...)) and
and as a whole the ValueTransformerSupplier interface.
We can use ValueTransformer/ValueTransformerWithKey type instead without
additional supplier layer.


Cheers,
Jeyhun


On Thu, May 25, 2017 at 1:07 AM Matthias J. Sax 
wrote:

> One more question:
>
> Should we add any of
>  - InitizialierWithKey
>  - ReducerWithKey
>  - ValueTransformerWithKey
>
> To get consistent/complete API, it might be a good idea. Any thoughts?
>
>
> -Matthias
>
>
> On 5/24/17 3:47 PM, Matthias J. Sax wrote:
> > Jeyhun,
> >
> > I was just wondering if you did look into the key-deep-copy idea we
> > discussed. I am curious to see what the impact might be.
> >
> >
> > -Matthias
> >
> > On 5/20/17 2:03 AM, Jeyhun Karimov wrote:
> >> Hi,
> >>
> >> Thanks for your comments. I rethink about including rich functions into
> >> this KIP.
> >> I think once we include rich functions in this KIP and then fix
> >> ProcessorContext in another KIP and incorporate with existing rich
> >> functions, the code will not be backwards compatible.
> >>
> >> I see Damian's and your point more clearly now.
> >>
> >> Conclusion: we include only withKey interfaces in this KIP (I updated
> the
> >> KIP), I will try also initiate another KIP for rich functions.
> >>
> >> Cheers,
> >> Jeyhun
> >>
> >> On Fri, May 19, 2017 at 10:50 PM Matthias J. Sax  >
> >> wrote:
> >>
> >>> With the current KIP, using ValueMapper and ValueMapperWithKey
> >>> interfaces, RichFunction seems to be an independent add-on. To fix the
> >>> original issue to allow key access, RichFunctions are not required
> IMHO.
> >>>
> >>> I initially put the RichFunction idea on the table, because I was
> hoping
> >>> to get a uniform API. And I think, is was good to consider them --
> >>> however, the discussion showed that they are not necessary for key
> >>> access. Thus, it seems to be better to handle RichFunctions in an own
> >>> KIP. The ProcessorContext/RecordContext issues seems to be a main
> >>> challenge for this. And introducing RichFunctions with parameter-less
> >>> init() method, seem not to help too much. We would get an
> "intermediate"
> >>> API that we want to change anyway later on...
> >>>
> >>> As you put already much effort into RichFunction, feel free do push
> this
> >>> further and start a new KIP (we can do this even in parallel) -- we
> >>> don't want to slow you down :) But it make the discussion and code
> >>> review easier, if we separate both IMHO.
> >>>
> >>>
> >>> -Matthias
> >>>
> >>>
> >>> On 5/19/17 2:25 AM, Jeyhun Karimov wrote:
>  Hi Damian,
> 
>  Thanks for your comments. I think providing to users *interface*
> rather
>  than *abstract class* should be preferred (Matthias also raised this
> >>> issue
>  ), anyway I changed the corresponding parts of KIP.
> 
>  Regarding with passing additional contextual information, I think it
> is a
>  tradeoff,
>  1) first, we fix the context parameter for *init() *method in another
> PR
>  and solve Rich functions afterwards
>  2) first, we fix the requested issues on jira ([1-3]) with providing
>  (not-complete) Rich functions and integrate the context parameters to
> >>> this
>  afterwards (like improvement)
> 
>  To me, the second approach seems more incremental. However you are
> right,
>  the names might confuse the users.
> 
> 
> 
>  [1] https://issues.apache.org/jira/browse/KAFKA-4218
>  [2] https://issues.apache.org/jira/browse/KAFKA-4726
>  [3] https://issues.apache.org/jira/browse/KAFKA-3745
> 
> 
>  Cheers,
>  Jeyhun
> 
> 
>  On Fri, May 19, 2017 at 10:42 AM Damian Guy 
> >>> wrote:
> 
> > Hi,
> >
> > I see you've removed the `ProcessorContext` from the RichFunction
> which
> >>> is
> > good, but why is it a `RichFunction`? I'd have expected it to pass
> some
> > additional contextual information, i.e., the `RecordContext` that
> >>> contains
> > just the topic, partition, timestamp, offset.  I'm ok with it not
> >>> passing
> > this contextual information, but is the naming incorrect? I'm not
> sure,
> > tbh. I'm wondering if we should drop `RichFunctions` until we 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

One more question:

Should we add any of
 - InitizialierWithKey
 - ReducerWithKey
 - ValueTransformerWithKey

To get consistent/complete API, it might be a good idea. Any thoughts?


-Matthias


On 5/24/17 3:47 PM, Matthias J. Sax wrote:
> Jeyhun,
> 
> I was just wondering if you did look into the key-deep-copy idea we
> discussed. I am curious to see what the impact might be.
> 
> 
> -Matthias
> 
> On 5/20/17 2:03 AM, Jeyhun Karimov wrote:
>> Hi,
>>
>> Thanks for your comments. I rethink about including rich functions into
>> this KIP.
>> I think once we include rich functions in this KIP and then fix
>> ProcessorContext in another KIP and incorporate with existing rich
>> functions, the code will not be backwards compatible.
>>
>> I see Damian's and your point more clearly now.
>>
>> Conclusion: we include only withKey interfaces in this KIP (I updated the
>> KIP), I will try also initiate another KIP for rich functions.
>>
>> Cheers,
>> Jeyhun
>>
>> On Fri, May 19, 2017 at 10:50 PM Matthias J. Sax 
>> wrote:
>>
>>> With the current KIP, using ValueMapper and ValueMapperWithKey
>>> interfaces, RichFunction seems to be an independent add-on. To fix the
>>> original issue to allow key access, RichFunctions are not required IMHO.
>>>
>>> I initially put the RichFunction idea on the table, because I was hoping
>>> to get a uniform API. And I think, is was good to consider them --
>>> however, the discussion showed that they are not necessary for key
>>> access. Thus, it seems to be better to handle RichFunctions in an own
>>> KIP. The ProcessorContext/RecordContext issues seems to be a main
>>> challenge for this. And introducing RichFunctions with parameter-less
>>> init() method, seem not to help too much. We would get an "intermediate"
>>> API that we want to change anyway later on...
>>>
>>> As you put already much effort into RichFunction, feel free do push this
>>> further and start a new KIP (we can do this even in parallel) -- we
>>> don't want to slow you down :) But it make the discussion and code
>>> review easier, if we separate both IMHO.
>>>
>>>
>>> -Matthias
>>>
>>>
>>> On 5/19/17 2:25 AM, Jeyhun Karimov wrote:
 Hi Damian,

 Thanks for your comments. I think providing to users *interface* rather
 than *abstract class* should be preferred (Matthias also raised this
>>> issue
 ), anyway I changed the corresponding parts of KIP.

 Regarding with passing additional contextual information, I think it is a
 tradeoff,
 1) first, we fix the context parameter for *init() *method in another PR
 and solve Rich functions afterwards
 2) first, we fix the requested issues on jira ([1-3]) with providing
 (not-complete) Rich functions and integrate the context parameters to
>>> this
 afterwards (like improvement)

 To me, the second approach seems more incremental. However you are right,
 the names might confuse the users.



 [1] https://issues.apache.org/jira/browse/KAFKA-4218
 [2] https://issues.apache.org/jira/browse/KAFKA-4726
 [3] https://issues.apache.org/jira/browse/KAFKA-3745


 Cheers,
 Jeyhun


 On Fri, May 19, 2017 at 10:42 AM Damian Guy 
>>> wrote:

> Hi,
>
> I see you've removed the `ProcessorContext` from the RichFunction which
>>> is
> good, but why is it a `RichFunction`? I'd have expected it to pass some
> additional contextual information, i.e., the `RecordContext` that
>>> contains
> just the topic, partition, timestamp, offset.  I'm ok with it not
>>> passing
> this contextual information, but is the naming incorrect? I'm not sure,
> tbh. I'm wondering if we should drop `RichFunctions` until we can do it
> properly with the correct context?
>
> Also, i don't like the abstract classes: RichValueMapper,
>>> RichValueJoiner,
> RichInitializer etc. Why can't they not just be interfaces? Generally we
> should provide users with Intefaces to code against, not classes.
>
> Thanks,
> Damian
>
> On Fri, 19 May 2017 at 00:50 Jeyhun Karimov 
>>> wrote:
>
>> Hi,
>>
>> Thanks. I initiated the PR as well, to get a better overview.
>>
>> The only reason that I used abstract class instead of interface for
>>> Rich
>> functions is that in future if we will have some AbstractRichFunction
>> abstract classes,
>> we can easily extend:
>>
>> public abstract class RichValueMapper  implements
>> ValueMapperWithKey, RichFunction *extends
> AbstractRichFunction*{
>> }
>>  With interfaces we are only limited to interfaces for inheritance.
>>
>> However, I think we can easily change it (from abstract class ->
> interface)
>> if you think interface is a better fit.
>>
>>
>> Cheers,
>> Jeyhun
>>
>>
>> On Fri, May 19, 2017 at 1:00 AM 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Jeyhun,

I was just wondering if you did look into the key-deep-copy idea we
discussed. I am curious to see what the impact might be.


-Matthias

On 5/20/17 2:03 AM, Jeyhun Karimov wrote:
> Hi,
> 
> Thanks for your comments. I rethink about including rich functions into
> this KIP.
> I think once we include rich functions in this KIP and then fix
> ProcessorContext in another KIP and incorporate with existing rich
> functions, the code will not be backwards compatible.
> 
> I see Damian's and your point more clearly now.
> 
> Conclusion: we include only withKey interfaces in this KIP (I updated the
> KIP), I will try also initiate another KIP for rich functions.
> 
> Cheers,
> Jeyhun
> 
> On Fri, May 19, 2017 at 10:50 PM Matthias J. Sax 
> wrote:
> 
>> With the current KIP, using ValueMapper and ValueMapperWithKey
>> interfaces, RichFunction seems to be an independent add-on. To fix the
>> original issue to allow key access, RichFunctions are not required IMHO.
>>
>> I initially put the RichFunction idea on the table, because I was hoping
>> to get a uniform API. And I think, is was good to consider them --
>> however, the discussion showed that they are not necessary for key
>> access. Thus, it seems to be better to handle RichFunctions in an own
>> KIP. The ProcessorContext/RecordContext issues seems to be a main
>> challenge for this. And introducing RichFunctions with parameter-less
>> init() method, seem not to help too much. We would get an "intermediate"
>> API that we want to change anyway later on...
>>
>> As you put already much effort into RichFunction, feel free do push this
>> further and start a new KIP (we can do this even in parallel) -- we
>> don't want to slow you down :) But it make the discussion and code
>> review easier, if we separate both IMHO.
>>
>>
>> -Matthias
>>
>>
>> On 5/19/17 2:25 AM, Jeyhun Karimov wrote:
>>> Hi Damian,
>>>
>>> Thanks for your comments. I think providing to users *interface* rather
>>> than *abstract class* should be preferred (Matthias also raised this
>> issue
>>> ), anyway I changed the corresponding parts of KIP.
>>>
>>> Regarding with passing additional contextual information, I think it is a
>>> tradeoff,
>>> 1) first, we fix the context parameter for *init() *method in another PR
>>> and solve Rich functions afterwards
>>> 2) first, we fix the requested issues on jira ([1-3]) with providing
>>> (not-complete) Rich functions and integrate the context parameters to
>> this
>>> afterwards (like improvement)
>>>
>>> To me, the second approach seems more incremental. However you are right,
>>> the names might confuse the users.
>>>
>>>
>>>
>>> [1] https://issues.apache.org/jira/browse/KAFKA-4218
>>> [2] https://issues.apache.org/jira/browse/KAFKA-4726
>>> [3] https://issues.apache.org/jira/browse/KAFKA-3745
>>>
>>>
>>> Cheers,
>>> Jeyhun
>>>
>>>
>>> On Fri, May 19, 2017 at 10:42 AM Damian Guy 
>> wrote:
>>>
 Hi,

 I see you've removed the `ProcessorContext` from the RichFunction which
>> is
 good, but why is it a `RichFunction`? I'd have expected it to pass some
 additional contextual information, i.e., the `RecordContext` that
>> contains
 just the topic, partition, timestamp, offset.  I'm ok with it not
>> passing
 this contextual information, but is the naming incorrect? I'm not sure,
 tbh. I'm wondering if we should drop `RichFunctions` until we can do it
 properly with the correct context?

 Also, i don't like the abstract classes: RichValueMapper,
>> RichValueJoiner,
 RichInitializer etc. Why can't they not just be interfaces? Generally we
 should provide users with Intefaces to code against, not classes.

 Thanks,
 Damian

 On Fri, 19 May 2017 at 00:50 Jeyhun Karimov 
>> wrote:

> Hi,
>
> Thanks. I initiated the PR as well, to get a better overview.
>
> The only reason that I used abstract class instead of interface for
>> Rich
> functions is that in future if we will have some AbstractRichFunction
> abstract classes,
> we can easily extend:
>
> public abstract class RichValueMapper  implements
> ValueMapperWithKey, RichFunction *extends
 AbstractRichFunction*{
> }
>  With interfaces we are only limited to interfaces for inheritance.
>
> However, I think we can easily change it (from abstract class ->
 interface)
> if you think interface is a better fit.
>
>
> Cheers,
> Jeyhun
>
>
> On Fri, May 19, 2017 at 1:00 AM Matthias J. Sax >>
> wrote:
>
>> Thanks for the update and explanations. The KIP is quite improved now
 --
>> great job!
>>
>> One more question: Why are RichValueMapper etc abstract classes and
>> not
>> interfaces?
>>
>>
>> Overall, I like the KIP a lot!
>>
>>
>> -Matthias
>>
>>
>> On 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi,

Thanks for your comments. I rethink about including rich functions into
this KIP.
I think once we include rich functions in this KIP and then fix
ProcessorContext in another KIP and incorporate with existing rich
functions, the code will not be backwards compatible.

I see Damian's and your point more clearly now.

Conclusion: we include only withKey interfaces in this KIP (I updated the
KIP), I will try also initiate another KIP for rich functions.

Cheers,
Jeyhun

On Fri, May 19, 2017 at 10:50 PM Matthias J. Sax 
wrote:

> With the current KIP, using ValueMapper and ValueMapperWithKey
> interfaces, RichFunction seems to be an independent add-on. To fix the
> original issue to allow key access, RichFunctions are not required IMHO.
>
> I initially put the RichFunction idea on the table, because I was hoping
> to get a uniform API. And I think, is was good to consider them --
> however, the discussion showed that they are not necessary for key
> access. Thus, it seems to be better to handle RichFunctions in an own
> KIP. The ProcessorContext/RecordContext issues seems to be a main
> challenge for this. And introducing RichFunctions with parameter-less
> init() method, seem not to help too much. We would get an "intermediate"
> API that we want to change anyway later on...
>
> As you put already much effort into RichFunction, feel free do push this
> further and start a new KIP (we can do this even in parallel) -- we
> don't want to slow you down :) But it make the discussion and code
> review easier, if we separate both IMHO.
>
>
> -Matthias
>
>
> On 5/19/17 2:25 AM, Jeyhun Karimov wrote:
> > Hi Damian,
> >
> > Thanks for your comments. I think providing to users *interface* rather
> > than *abstract class* should be preferred (Matthias also raised this
> issue
> > ), anyway I changed the corresponding parts of KIP.
> >
> > Regarding with passing additional contextual information, I think it is a
> > tradeoff,
> > 1) first, we fix the context parameter for *init() *method in another PR
> > and solve Rich functions afterwards
> > 2) first, we fix the requested issues on jira ([1-3]) with providing
> > (not-complete) Rich functions and integrate the context parameters to
> this
> > afterwards (like improvement)
> >
> > To me, the second approach seems more incremental. However you are right,
> > the names might confuse the users.
> >
> >
> >
> > [1] https://issues.apache.org/jira/browse/KAFKA-4218
> > [2] https://issues.apache.org/jira/browse/KAFKA-4726
> > [3] https://issues.apache.org/jira/browse/KAFKA-3745
> >
> >
> > Cheers,
> > Jeyhun
> >
> >
> > On Fri, May 19, 2017 at 10:42 AM Damian Guy 
> wrote:
> >
> >> Hi,
> >>
> >> I see you've removed the `ProcessorContext` from the RichFunction which
> is
> >> good, but why is it a `RichFunction`? I'd have expected it to pass some
> >> additional contextual information, i.e., the `RecordContext` that
> contains
> >> just the topic, partition, timestamp, offset.  I'm ok with it not
> passing
> >> this contextual information, but is the naming incorrect? I'm not sure,
> >> tbh. I'm wondering if we should drop `RichFunctions` until we can do it
> >> properly with the correct context?
> >>
> >> Also, i don't like the abstract classes: RichValueMapper,
> RichValueJoiner,
> >> RichInitializer etc. Why can't they not just be interfaces? Generally we
> >> should provide users with Intefaces to code against, not classes.
> >>
> >> Thanks,
> >> Damian
> >>
> >> On Fri, 19 May 2017 at 00:50 Jeyhun Karimov 
> wrote:
> >>
> >>> Hi,
> >>>
> >>> Thanks. I initiated the PR as well, to get a better overview.
> >>>
> >>> The only reason that I used abstract class instead of interface for
> Rich
> >>> functions is that in future if we will have some AbstractRichFunction
> >>> abstract classes,
> >>> we can easily extend:
> >>>
> >>> public abstract class RichValueMapper  implements
> >>> ValueMapperWithKey, RichFunction *extends
> >> AbstractRichFunction*{
> >>> }
> >>>  With interfaces we are only limited to interfaces for inheritance.
> >>>
> >>> However, I think we can easily change it (from abstract class ->
> >> interface)
> >>> if you think interface is a better fit.
> >>>
> >>>
> >>> Cheers,
> >>> Jeyhun
> >>>
> >>>
> >>> On Fri, May 19, 2017 at 1:00 AM Matthias J. Sax  >
> >>> wrote:
> >>>
>  Thanks for the update and explanations. The KIP is quite improved now
> >> --
>  great job!
> 
>  One more question: Why are RichValueMapper etc abstract classes and
> not
>  interfaces?
> 
> 
>  Overall, I like the KIP a lot!
> 
> 
>  -Matthias
> 
> 
>  On 5/16/17 7:03 AM, Jeyhun Karimov wrote:
> > Hi,
> >
> > Thanks for your comments.
> >
> > I think supporting Lambdas for `withKey` and `AbstractRichFunction`
> >> don't go together, as Lambdas are only supported for interfaces
> >> AFAIK.

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

With the current KIP, using ValueMapper and ValueMapperWithKey
interfaces, RichFunction seems to be an independent add-on. To fix the
original issue to allow key access, RichFunctions are not required IMHO.

I initially put the RichFunction idea on the table, because I was hoping
to get a uniform API. And I think, is was good to consider them --
however, the discussion showed that they are not necessary for key
access. Thus, it seems to be better to handle RichFunctions in an own
KIP. The ProcessorContext/RecordContext issues seems to be a main
challenge for this. And introducing RichFunctions with parameter-less
init() method, seem not to help too much. We would get an "intermediate"
API that we want to change anyway later on...

As you put already much effort into RichFunction, feel free do push this
further and start a new KIP (we can do this even in parallel) -- we
don't want to slow you down :) But it make the discussion and code
review easier, if we separate both IMHO.


-Matthias


On 5/19/17 2:25 AM, Jeyhun Karimov wrote:
> Hi Damian,
> 
> Thanks for your comments. I think providing to users *interface* rather
> than *abstract class* should be preferred (Matthias also raised this issue
> ), anyway I changed the corresponding parts of KIP.
> 
> Regarding with passing additional contextual information, I think it is a
> tradeoff,
> 1) first, we fix the context parameter for *init() *method in another PR
> and solve Rich functions afterwards
> 2) first, we fix the requested issues on jira ([1-3]) with providing
> (not-complete) Rich functions and integrate the context parameters to this
> afterwards (like improvement)
> 
> To me, the second approach seems more incremental. However you are right,
> the names might confuse the users.
> 
> 
> 
> [1] https://issues.apache.org/jira/browse/KAFKA-4218
> [2] https://issues.apache.org/jira/browse/KAFKA-4726
> [3] https://issues.apache.org/jira/browse/KAFKA-3745
> 
> 
> Cheers,
> Jeyhun
> 
> 
> On Fri, May 19, 2017 at 10:42 AM Damian Guy  wrote:
> 
>> Hi,
>>
>> I see you've removed the `ProcessorContext` from the RichFunction which is
>> good, but why is it a `RichFunction`? I'd have expected it to pass some
>> additional contextual information, i.e., the `RecordContext` that contains
>> just the topic, partition, timestamp, offset.  I'm ok with it not passing
>> this contextual information, but is the naming incorrect? I'm not sure,
>> tbh. I'm wondering if we should drop `RichFunctions` until we can do it
>> properly with the correct context?
>>
>> Also, i don't like the abstract classes: RichValueMapper, RichValueJoiner,
>> RichInitializer etc. Why can't they not just be interfaces? Generally we
>> should provide users with Intefaces to code against, not classes.
>>
>> Thanks,
>> Damian
>>
>> On Fri, 19 May 2017 at 00:50 Jeyhun Karimov  wrote:
>>
>>> Hi,
>>>
>>> Thanks. I initiated the PR as well, to get a better overview.
>>>
>>> The only reason that I used abstract class instead of interface for Rich
>>> functions is that in future if we will have some AbstractRichFunction
>>> abstract classes,
>>> we can easily extend:
>>>
>>> public abstract class RichValueMapper  implements
>>> ValueMapperWithKey, RichFunction *extends
>> AbstractRichFunction*{
>>> }
>>>  With interfaces we are only limited to interfaces for inheritance.
>>>
>>> However, I think we can easily change it (from abstract class ->
>> interface)
>>> if you think interface is a better fit.
>>>
>>>
>>> Cheers,
>>> Jeyhun
>>>
>>>
>>> On Fri, May 19, 2017 at 1:00 AM Matthias J. Sax 
>>> wrote:
>>>
 Thanks for the update and explanations. The KIP is quite improved now
>> --
 great job!

 One more question: Why are RichValueMapper etc abstract classes and not
 interfaces?


 Overall, I like the KIP a lot!


 -Matthias


 On 5/16/17 7:03 AM, Jeyhun Karimov wrote:
> Hi,
>
> Thanks for your comments.
>
> I think supporting Lambdas for `withKey` and `AbstractRichFunction`
>> don't go together, as Lambdas are only supported for interfaces
>> AFAIK.
>
>
> Maybe I misunderstood your comment.
> *withKey* and and *withOnlyValue* are interfaces. So they don't have
 direct
> relation with *AbstractRichFunction*.
> *withKey* and and *withOnlyValue* interfaces have only one  method ,
>> so
 we
> can use lambdas.
> Where does the *AbstractRichFunction* comes to play? Inside Rich
 functions.
> And we use Rich functions in 2 places:
>
> 1. User doesn't use rich functions. Just regular *withKey* and and
> *withOnlyValue* interfaces(both support lambdas) . We get those
 interfaces
> and wrap into Rich function while building the topology, and send to
> Processor.
> 2. User does use rich functions (Rich functions implement *withKey*
> interface). As a result no lamdas here 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi Damian,

Thanks for your comments. I think providing to users *interface* rather
than *abstract class* should be preferred (Matthias also raised this issue
), anyway I changed the corresponding parts of KIP.

Regarding with passing additional contextual information, I think it is a
tradeoff,
1) first, we fix the context parameter for *init() *method in another PR
and solve Rich functions afterwards
2) first, we fix the requested issues on jira ([1-3]) with providing
(not-complete) Rich functions and integrate the context parameters to this
afterwards (like improvement)

To me, the second approach seems more incremental. However you are right,
the names might confuse the users.



[1] https://issues.apache.org/jira/browse/KAFKA-4218
[2] https://issues.apache.org/jira/browse/KAFKA-4726
[3] https://issues.apache.org/jira/browse/KAFKA-3745


Cheers,
Jeyhun


On Fri, May 19, 2017 at 10:42 AM Damian Guy  wrote:

> Hi,
>
> I see you've removed the `ProcessorContext` from the RichFunction which is
> good, but why is it a `RichFunction`? I'd have expected it to pass some
> additional contextual information, i.e., the `RecordContext` that contains
> just the topic, partition, timestamp, offset.  I'm ok with it not passing
> this contextual information, but is the naming incorrect? I'm not sure,
> tbh. I'm wondering if we should drop `RichFunctions` until we can do it
> properly with the correct context?
>
> Also, i don't like the abstract classes: RichValueMapper, RichValueJoiner,
> RichInitializer etc. Why can't they not just be interfaces? Generally we
> should provide users with Intefaces to code against, not classes.
>
> Thanks,
> Damian
>
> On Fri, 19 May 2017 at 00:50 Jeyhun Karimov  wrote:
>
> > Hi,
> >
> > Thanks. I initiated the PR as well, to get a better overview.
> >
> > The only reason that I used abstract class instead of interface for Rich
> > functions is that in future if we will have some AbstractRichFunction
> > abstract classes,
> > we can easily extend:
> >
> > public abstract class RichValueMapper  implements
> > ValueMapperWithKey, RichFunction *extends
> AbstractRichFunction*{
> > }
> >  With interfaces we are only limited to interfaces for inheritance.
> >
> > However, I think we can easily change it (from abstract class ->
> interface)
> > if you think interface is a better fit.
> >
> >
> > Cheers,
> > Jeyhun
> >
> >
> > On Fri, May 19, 2017 at 1:00 AM Matthias J. Sax 
> > wrote:
> >
> > > Thanks for the update and explanations. The KIP is quite improved now
> --
> > > great job!
> > >
> > > One more question: Why are RichValueMapper etc abstract classes and not
> > > interfaces?
> > >
> > >
> > > Overall, I like the KIP a lot!
> > >
> > >
> > > -Matthias
> > >
> > >
> > > On 5/16/17 7:03 AM, Jeyhun Karimov wrote:
> > > > Hi,
> > > >
> > > > Thanks for your comments.
> > > >
> > > > I think supporting Lambdas for `withKey` and `AbstractRichFunction`
> > > >> don't go together, as Lambdas are only supported for interfaces
> AFAIK.
> > > >
> > > >
> > > > Maybe I misunderstood your comment.
> > > > *withKey* and and *withOnlyValue* are interfaces. So they don't have
> > > direct
> > > > relation with *AbstractRichFunction*.
> > > > *withKey* and and *withOnlyValue* interfaces have only one  method ,
> so
> > > we
> > > > can use lambdas.
> > > > Where does the *AbstractRichFunction* comes to play? Inside Rich
> > > functions.
> > > > And we use Rich functions in 2 places:
> > > >
> > > > 1. User doesn't use rich functions. Just regular *withKey* and and
> > > > *withOnlyValue* interfaces(both support lambdas) . We get those
> > > interfaces
> > > > and wrap into Rich function while building the topology, and send to
> > > > Processor.
> > > > 2. User does use rich functions (Rich functions implement *withKey*
> > > > interface). As a result no lamdas here by definition. In this case,
> > while
> > > > building the topology we do a type check if the object type is
> > > > *withKey* or *RichFunction*.
> > > >
> > > > So *AbstractRichFunction* is just syntactic sugar for Rich functions
> > and
> > > > does not affect using lambdas.
> > > >
> > > > Thus, if we want to support Lambdas for `withKey`, we need to have a
> > > >> interface approach like this
> > > >>   - RichFunction -> only adding init() and close()
> > > >>   - ValueMapper
> > > >>   - ValueMapperWithKey
> > > >>   - RichValueMapper extends ValueMapperWithKey, RichFunction
> > > >
> > > >
> > > > As I said above, currently we support lambdas for *withKey*
> interfaces
> > as
> > > > well.  However, I agree with your idea and I will remove the
> > > > AbstractRichFunction from the design.
> > > >
> > > > As an alternative, we could argue, that it is sufficient to support
> > > >> Lambdas for the "plain" API only, but not for any "extended API".
> For
> > > >> this, RichFunction could add key+init+close and AbstractRichFunction
> > > >> would 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Damian Guy]

Hi,

I see you've removed the `ProcessorContext` from the RichFunction which is
good, but why is it a `RichFunction`? I'd have expected it to pass some
additional contextual information, i.e., the `RecordContext` that contains
just the topic, partition, timestamp, offset.  I'm ok with it not passing
this contextual information, but is the naming incorrect? I'm not sure,
tbh. I'm wondering if we should drop `RichFunctions` until we can do it
properly with the correct context?

Also, i don't like the abstract classes: RichValueMapper, RichValueJoiner,
RichInitializer etc. Why can't they not just be interfaces? Generally we
should provide users with Intefaces to code against, not classes.

Thanks,
Damian

On Fri, 19 May 2017 at 00:50 Jeyhun Karimov  wrote:

> Hi,
>
> Thanks. I initiated the PR as well, to get a better overview.
>
> The only reason that I used abstract class instead of interface for Rich
> functions is that in future if we will have some AbstractRichFunction
> abstract classes,
> we can easily extend:
>
> public abstract class RichValueMapper  implements
> ValueMapperWithKey, RichFunction *extends  AbstractRichFunction*{
> }
>  With interfaces we are only limited to interfaces for inheritance.
>
> However, I think we can easily change it (from abstract class -> interface)
> if you think interface is a better fit.
>
>
> Cheers,
> Jeyhun
>
>
> On Fri, May 19, 2017 at 1:00 AM Matthias J. Sax 
> wrote:
>
> > Thanks for the update and explanations. The KIP is quite improved now --
> > great job!
> >
> > One more question: Why are RichValueMapper etc abstract classes and not
> > interfaces?
> >
> >
> > Overall, I like the KIP a lot!
> >
> >
> > -Matthias
> >
> >
> > On 5/16/17 7:03 AM, Jeyhun Karimov wrote:
> > > Hi,
> > >
> > > Thanks for your comments.
> > >
> > > I think supporting Lambdas for `withKey` and `AbstractRichFunction`
> > >> don't go together, as Lambdas are only supported for interfaces AFAIK.
> > >
> > >
> > > Maybe I misunderstood your comment.
> > > *withKey* and and *withOnlyValue* are interfaces. So they don't have
> > direct
> > > relation with *AbstractRichFunction*.
> > > *withKey* and and *withOnlyValue* interfaces have only one  method , so
> > we
> > > can use lambdas.
> > > Where does the *AbstractRichFunction* comes to play? Inside Rich
> > functions.
> > > And we use Rich functions in 2 places:
> > >
> > > 1. User doesn't use rich functions. Just regular *withKey* and and
> > > *withOnlyValue* interfaces(both support lambdas) . We get those
> > interfaces
> > > and wrap into Rich function while building the topology, and send to
> > > Processor.
> > > 2. User does use rich functions (Rich functions implement *withKey*
> > > interface). As a result no lamdas here by definition. In this case,
> while
> > > building the topology we do a type check if the object type is
> > > *withKey* or *RichFunction*.
> > >
> > > So *AbstractRichFunction* is just syntactic sugar for Rich functions
> and
> > > does not affect using lambdas.
> > >
> > > Thus, if we want to support Lambdas for `withKey`, we need to have a
> > >> interface approach like this
> > >>   - RichFunction -> only adding init() and close()
> > >>   - ValueMapper
> > >>   - ValueMapperWithKey
> > >>   - RichValueMapper extends ValueMapperWithKey, RichFunction
> > >
> > >
> > > As I said above, currently we support lambdas for *withKey* interfaces
> as
> > > well.  However, I agree with your idea and I will remove the
> > > AbstractRichFunction from the design.
> > >
> > > As an alternative, we could argue, that it is sufficient to support
> > >> Lambdas for the "plain" API only, but not for any "extended API". For
> > >> this, RichFunction could add key+init+close and AbstractRichFunction
> > >> would allow to only care about getting the key.
> > >> Not sure, which one is better. I don't like the idea of more
> overloaded
> > >> methods to get Lambdas for `withKey` interfaces too much because we
> have
> > >> already so many overlaods. On the other hand, I do see value in
> > >> supporting Lambdas for `withKey`.
> > >
> > >
> > > Just to clarify, with current design we have only one extra overloaded
> > > method per *withOnlyValue* interface:  which is *withKey* version of
> > > particular interface.
> > > We don't need extra overload for Rich function as Rich function
> > implements
> > > *withKey* interface as a result they have same type. We differentiate
> > them
> > > while building the topology.
> > > We supported lambdas for *withKey* APIs because of the comment:
> > >
> > > @Jeyhun: I did not put any thought into this, but can we have a design
> > >> that allows for both? Also, with regard to lambdas, it might make
> sense
> > >> to allow for both `V -> newV` and `(K, V) -> newV` ?
> > >
> > >
> > > However, I don't think that this complicates the overall design
> > > significantly.
> > >
> > >
> > > Depending on what we want to support, it 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi,

Thanks. I initiated the PR as well, to get a better overview.

The only reason that I used abstract class instead of interface for Rich
functions is that in future if we will have some AbstractRichFunction
abstract classes,
we can easily extend:

public abstract class RichValueMapper  implements
ValueMapperWithKey, RichFunction *extends  AbstractRichFunction*{
}
 With interfaces we are only limited to interfaces for inheritance.

However, I think we can easily change it (from abstract class -> interface)
if you think interface is a better fit.


Cheers,
Jeyhun


On Fri, May 19, 2017 at 1:00 AM Matthias J. Sax 
wrote:

> Thanks for the update and explanations. The KIP is quite improved now --
> great job!
>
> One more question: Why are RichValueMapper etc abstract classes and not
> interfaces?
>
>
> Overall, I like the KIP a lot!
>
>
> -Matthias
>
>
> On 5/16/17 7:03 AM, Jeyhun Karimov wrote:
> > Hi,
> >
> > Thanks for your comments.
> >
> > I think supporting Lambdas for `withKey` and `AbstractRichFunction`
> >> don't go together, as Lambdas are only supported for interfaces AFAIK.
> >
> >
> > Maybe I misunderstood your comment.
> > *withKey* and and *withOnlyValue* are interfaces. So they don't have
> direct
> > relation with *AbstractRichFunction*.
> > *withKey* and and *withOnlyValue* interfaces have only one  method , so
> we
> > can use lambdas.
> > Where does the *AbstractRichFunction* comes to play? Inside Rich
> functions.
> > And we use Rich functions in 2 places:
> >
> > 1. User doesn't use rich functions. Just regular *withKey* and and
> > *withOnlyValue* interfaces(both support lambdas) . We get those
> interfaces
> > and wrap into Rich function while building the topology, and send to
> > Processor.
> > 2. User does use rich functions (Rich functions implement *withKey*
> > interface). As a result no lamdas here by definition. In this case, while
> > building the topology we do a type check if the object type is
> > *withKey* or *RichFunction*.
> >
> > So *AbstractRichFunction* is just syntactic sugar for Rich functions and
> > does not affect using lambdas.
> >
> > Thus, if we want to support Lambdas for `withKey`, we need to have a
> >> interface approach like this
> >>   - RichFunction -> only adding init() and close()
> >>   - ValueMapper
> >>   - ValueMapperWithKey
> >>   - RichValueMapper extends ValueMapperWithKey, RichFunction
> >
> >
> > As I said above, currently we support lambdas for *withKey* interfaces as
> > well.  However, I agree with your idea and I will remove the
> > AbstractRichFunction from the design.
> >
> > As an alternative, we could argue, that it is sufficient to support
> >> Lambdas for the "plain" API only, but not for any "extended API". For
> >> this, RichFunction could add key+init+close and AbstractRichFunction
> >> would allow to only care about getting the key.
> >> Not sure, which one is better. I don't like the idea of more overloaded
> >> methods to get Lambdas for `withKey` interfaces too much because we have
> >> already so many overlaods. On the other hand, I do see value in
> >> supporting Lambdas for `withKey`.
> >
> >
> > Just to clarify, with current design we have only one extra overloaded
> > method per *withOnlyValue* interface:  which is *withKey* version of
> > particular interface.
> > We don't need extra overload for Rich function as Rich function
> implements
> > *withKey* interface as a result they have same type. We differentiate
> them
> > while building the topology.
> > We supported lambdas for *withKey* APIs because of the comment:
> >
> > @Jeyhun: I did not put any thought into this, but can we have a design
> >> that allows for both? Also, with regard to lambdas, it might make sense
> >> to allow for both `V -> newV` and `(K, V) -> newV` ?
> >
> >
> > However, I don't think that this complicates the overall design
> > significantly.
> >
> >
> > Depending on what we want to support, it might make sense to
> >> include/exclude RichFunctions from this KIP -- and thus, this also
> >> determines if we should have a "ProcessorContext KIP" before driving
> >> this KIP further.
> >
> >
> > Based on our discussion I think we should keep Rich functions as I don't
> > think that they bring extra layer of overhead to library.
> >
> > Any comments are appreciated.
> >
> > Cheers,
> > Jeyhun
> >
> >
> > On Tue, May 16, 2017 at 12:10 AM Matthias J. Sax 
> > wrote:
> >
> >> Jeyhun,
> >>
> >> thanks for the update.
> >>
> >> I think supporting Lambdas for `withKey` and `AbstractRichFunction`
> >> don't go together, as Lambdas are only supported for interfaces AFAIK.
> >>
> >> Thus, if we want to support Lambdas for `withKey`, we need to have a
> >> interface approach like this
> >>
> >>   - RichFunction -> only adding init() and close()
> >>
> >>   - ValueMapper
> >>   - ValueMapperWithKey
> >>
> >>   - RichValueMapper extends ValueMapperWithKey, RichFunction
> >>
> >> For this 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Thanks for the update and explanations. The KIP is quite improved now --
great job!

One more question: Why are RichValueMapper etc abstract classes and not
interfaces?


Overall, I like the KIP a lot!


-Matthias


On 5/16/17 7:03 AM, Jeyhun Karimov wrote:
> Hi,
> 
> Thanks for your comments.
> 
> I think supporting Lambdas for `withKey` and `AbstractRichFunction`
>> don't go together, as Lambdas are only supported for interfaces AFAIK.
> 
> 
> Maybe I misunderstood your comment.
> *withKey* and and *withOnlyValue* are interfaces. So they don't have direct
> relation with *AbstractRichFunction*.
> *withKey* and and *withOnlyValue* interfaces have only one  method , so we
> can use lambdas.
> Where does the *AbstractRichFunction* comes to play? Inside Rich functions.
> And we use Rich functions in 2 places:
> 
> 1. User doesn't use rich functions. Just regular *withKey* and and
> *withOnlyValue* interfaces(both support lambdas) . We get those interfaces
> and wrap into Rich function while building the topology, and send to
> Processor.
> 2. User does use rich functions (Rich functions implement *withKey*
> interface). As a result no lamdas here by definition. In this case, while
> building the topology we do a type check if the object type is
> *withKey* or *RichFunction*.
> 
> So *AbstractRichFunction* is just syntactic sugar for Rich functions and
> does not affect using lambdas.
> 
> Thus, if we want to support Lambdas for `withKey`, we need to have a
>> interface approach like this
>>   - RichFunction -> only adding init() and close()
>>   - ValueMapper
>>   - ValueMapperWithKey
>>   - RichValueMapper extends ValueMapperWithKey, RichFunction
> 
> 
> As I said above, currently we support lambdas for *withKey* interfaces as
> well.  However, I agree with your idea and I will remove the
> AbstractRichFunction from the design.
> 
> As an alternative, we could argue, that it is sufficient to support
>> Lambdas for the "plain" API only, but not for any "extended API". For
>> this, RichFunction could add key+init+close and AbstractRichFunction
>> would allow to only care about getting the key.
>> Not sure, which one is better. I don't like the idea of more overloaded
>> methods to get Lambdas for `withKey` interfaces too much because we have
>> already so many overlaods. On the other hand, I do see value in
>> supporting Lambdas for `withKey`.
> 
> 
> Just to clarify, with current design we have only one extra overloaded
> method per *withOnlyValue* interface:  which is *withKey* version of
> particular interface.
> We don't need extra overload for Rich function as Rich function implements
> *withKey* interface as a result they have same type. We differentiate them
> while building the topology.
> We supported lambdas for *withKey* APIs because of the comment:
> 
> @Jeyhun: I did not put any thought into this, but can we have a design
>> that allows for both? Also, with regard to lambdas, it might make sense
>> to allow for both `V -> newV` and `(K, V) -> newV` ?
> 
> 
> However, I don't think that this complicates the overall design
> significantly.
> 
> 
> Depending on what we want to support, it might make sense to
>> include/exclude RichFunctions from this KIP -- and thus, this also
>> determines if we should have a "ProcessorContext KIP" before driving
>> this KIP further.
> 
> 
> Based on our discussion I think we should keep Rich functions as I don't
> think that they bring extra layer of overhead to library.
> 
> Any comments are appreciated.
> 
> Cheers,
> Jeyhun
> 
> 
> On Tue, May 16, 2017 at 12:10 AM Matthias J. Sax 
> wrote:
> 
>> Jeyhun,
>>
>> thanks for the update.
>>
>> I think supporting Lambdas for `withKey` and `AbstractRichFunction`
>> don't go together, as Lambdas are only supported for interfaces AFAIK.
>>
>> Thus, if we want to support Lambdas for `withKey`, we need to have a
>> interface approach like this
>>
>>   - RichFunction -> only adding init() and close()
>>
>>   - ValueMapper
>>   - ValueMapperWithKey
>>
>>   - RichValueMapper extends ValueMapperWithKey, RichFunction
>>
>> For this approach, AbstractRichFunction does not make sense anymore, as
>> the only purpose of `RichFunction` is to allow the implementation of
>> init() and close() -- if you don't want those, you would implement a
>> different interface (ie, ValueMapperWithKey)
>>
>> As an alternative, we could argue, that it is sufficient to support
>> Lambdas for the "plain" API only, but not for any "extended API". For
>> this, RichFunction could add key+init+close and AbstractRichFunction
>> would allow to only care about getting the key.
>>
>> Not sure, which one is better. I don't like the idea of more overloaded
>> methods to get Lambdas for `withKey` interfaces too much because we have
>> already so many overlaods. On the other hand, I do see value in
>> supporting Lambdas for `withKey`.
>>
>> Depending on what we want to support, it might make sense to
>> include/exclude RichFunctions from 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi,

Thanks for your comments.

I think supporting Lambdas for `withKey` and `AbstractRichFunction`
> don't go together, as Lambdas are only supported for interfaces AFAIK.


Maybe I misunderstood your comment.
*withKey* and and *withOnlyValue* are interfaces. So they don't have direct
relation with *AbstractRichFunction*.
*withKey* and and *withOnlyValue* interfaces have only one  method , so we
can use lambdas.
Where does the *AbstractRichFunction* comes to play? Inside Rich functions.
And we use Rich functions in 2 places:

1. User doesn't use rich functions. Just regular *withKey* and and
*withOnlyValue* interfaces(both support lambdas) . We get those interfaces
and wrap into Rich function while building the topology, and send to
Processor.
2. User does use rich functions (Rich functions implement *withKey*
interface). As a result no lamdas here by definition. In this case, while
building the topology we do a type check if the object type is
*withKey* or *RichFunction*.

So *AbstractRichFunction* is just syntactic sugar for Rich functions and
does not affect using lambdas.

Thus, if we want to support Lambdas for `withKey`, we need to have a
> interface approach like this
>   - RichFunction -> only adding init() and close()
>   - ValueMapper
>   - ValueMapperWithKey
>   - RichValueMapper extends ValueMapperWithKey, RichFunction


As I said above, currently we support lambdas for *withKey* interfaces as
well.  However, I agree with your idea and I will remove the
AbstractRichFunction from the design.

As an alternative, we could argue, that it is sufficient to support
> Lambdas for the "plain" API only, but not for any "extended API". For
> this, RichFunction could add key+init+close and AbstractRichFunction
> would allow to only care about getting the key.
> Not sure, which one is better. I don't like the idea of more overloaded
> methods to get Lambdas for `withKey` interfaces too much because we have
> already so many overlaods. On the other hand, I do see value in
> supporting Lambdas for `withKey`.


Just to clarify, with current design we have only one extra overloaded
method per *withOnlyValue* interface:  which is *withKey* version of
particular interface.
We don't need extra overload for Rich function as Rich function implements
*withKey* interface as a result they have same type. We differentiate them
while building the topology.
We supported lambdas for *withKey* APIs because of the comment:

@Jeyhun: I did not put any thought into this, but can we have a design
> that allows for both? Also, with regard to lambdas, it might make sense
> to allow for both `V -> newV` and `(K, V) -> newV` ?


However, I don't think that this complicates the overall design
significantly.


Depending on what we want to support, it might make sense to
> include/exclude RichFunctions from this KIP -- and thus, this also
> determines if we should have a "ProcessorContext KIP" before driving
> this KIP further.


Based on our discussion I think we should keep Rich functions as I don't
think that they bring extra layer of overhead to library.

Any comments are appreciated.

Cheers,
Jeyhun


On Tue, May 16, 2017 at 12:10 AM Matthias J. Sax 
wrote:

> Jeyhun,
>
> thanks for the update.
>
> I think supporting Lambdas for `withKey` and `AbstractRichFunction`
> don't go together, as Lambdas are only supported for interfaces AFAIK.
>
> Thus, if we want to support Lambdas for `withKey`, we need to have a
> interface approach like this
>
>   - RichFunction -> only adding init() and close()
>
>   - ValueMapper
>   - ValueMapperWithKey
>
>   - RichValueMapper extends ValueMapperWithKey, RichFunction
>
> For this approach, AbstractRichFunction does not make sense anymore, as
> the only purpose of `RichFunction` is to allow the implementation of
> init() and close() -- if you don't want those, you would implement a
> different interface (ie, ValueMapperWithKey)
>
> As an alternative, we could argue, that it is sufficient to support
> Lambdas for the "plain" API only, but not for any "extended API". For
> this, RichFunction could add key+init+close and AbstractRichFunction
> would allow to only care about getting the key.
>
> Not sure, which one is better. I don't like the idea of more overloaded
> methods to get Lambdas for `withKey` interfaces too much because we have
> already so many overlaods. On the other hand, I do see value in
> supporting Lambdas for `withKey`.
>
> Depending on what we want to support, it might make sense to
> include/exclude RichFunctions from this KIP -- and thus, this also
> determines if we should have a "ProcessorContext KIP" before driving
> this KIP further.
>
> Thoughts?
>
>
>
>
> -Matthias
>
>
> On 5/15/17 11:01 AM, Jeyhun Karimov wrote:
> > Hi,
> >
> > Sorry for super late response. Thanks for your comments.
> >
> > I am not an expert on Lambdas. Can you elaborate a little bit? I cannot
> >> follow the explanation in the KIP to see what the problem is.
> >
> >
> > - From 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Jeyhun,

thanks for the update.

I think supporting Lambdas for `withKey` and `AbstractRichFunction`
don't go together, as Lambdas are only supported for interfaces AFAIK.

Thus, if we want to support Lambdas for `withKey`, we need to have a
interface approach like this

  - RichFunction -> only adding init() and close()

  - ValueMapper
  - ValueMapperWithKey

  - RichValueMapper extends ValueMapperWithKey, RichFunction

For this approach, AbstractRichFunction does not make sense anymore, as
the only purpose of `RichFunction` is to allow the implementation of
init() and close() -- if you don't want those, you would implement a
different interface (ie, ValueMapperWithKey)

As an alternative, we could argue, that it is sufficient to support
Lambdas for the "plain" API only, but not for any "extended API". For
this, RichFunction could add key+init+close and AbstractRichFunction
would allow to only care about getting the key.

Not sure, which one is better. I don't like the idea of more overloaded
methods to get Lambdas for `withKey` interfaces too much because we have
already so many overlaods. On the other hand, I do see value in
supporting Lambdas for `withKey`.

Depending on what we want to support, it might make sense to
include/exclude RichFunctions from this KIP -- and thus, this also
determines if we should have a "ProcessorContext KIP" before driving
this KIP further.

Thoughts?




-Matthias


On 5/15/17 11:01 AM, Jeyhun Karimov wrote:
> Hi,
> 
> Sorry for super late response. Thanks for your comments.
> 
> I am not an expert on Lambdas. Can you elaborate a little bit? I cannot
>> follow the explanation in the KIP to see what the problem is.
> 
> 
> - From [1] says "A functional interface is an interface that has just one
> abstract method, and thus represents a single function contract".
> So basically once we extend some interface from another (in our case,
> ValueMapperWithKey from ValueMapper) we cannot use lambdas in the extended
> interface.
> 
> 
> Further comments:
>>  - The KIP get a little hard to read -- can you maybe reformat the wiki
>> page a little bit? I think using `CodeBlock` would help.
> 
> 
> - I will work on the KIP.
> 
>  - What about KStream-KTable joins? You don't have overlaods added for
>> them. Why? (Even if I still hope that we don't need to add any new
>> overloads)
> 
> 
> - Actually there are more than one Processor and public APIs to be
> changed (KStream-KTable
> joins is one case). However all of them has similar structure: we overload
> the *method* with  *methodWithKey*,
> wrap it into the Rich function, send to processor and inside the processor
> call *init* and *close* methods of the Rich function.
> As I wrote in KIP, I wanted to demonstrate the overall idea with only
> *ValueMapper* as the same can be applied to all changes.
> Anyway I will update the KIP.
> 
>  - Why do we need `AbstractRichFunction`?
> 
> 
> Instead of overriding the *init(ProcessorContext p)* and* close()* methods
> in every Rich function with empty body like:
> 
> @Override
> void init(ProcessorContext context) {}
> 
> @Override
> void close () {}
> 
> I thought that we can override them once in *AbstractRichFunction* and
> extent new Rich functions from *AbstractRichFunction*.
> Basically this can eliminate code copy-paste and ease the maintenance.
> 
>  - What about interfaces Initializer, ForeachAction, Merger, Predicate,
>> Reducer? I don't want to say we should/need to add to all, but we should
>> discuss all of them and add where it does make sense (e.g.,
>> RichForachAction does make sense IMHO)
> 
> 
> Definitely agree. As I said, the same technique applies to all this
> interfaces and I didn't want to explode the KIP, just wanted to give the
> overall intuition.
> However, I will update the KIP as I said.
> 
> 
> Btw: I like the hierarchy `ValueXX` -- `ValueXXWithKey` -- `RichValueXX`
>> in general -- but why can't we do all this with interfaces only?
> 
> 
> Sure we can. However the main intuition is we should not force users to
> implement *init(ProcessorContext)* and *close()* functions every time they
> use Rich functions.
> If one needs, she can override the respective methods. However, I am open
> for discussion.
> 
> 
> I'd rather not see the use of  `ProcessorContext` spread any further than
>> it currently is. So maybe we need another KIP that is done before this?
>> Otherwise i think the scope of this KIP is becoming too large.
> 
> 
> That is good point. I wanted to make *init(ProcessorContext)* method
> persistent among the library (which use ProcessorContext as an input),
> therefore I put *ProcessorContext* as an input.
> So the important question is that (as @dguy and @mjsax mentioned) whether
> continue this KIP without providing users an access to *ProcessorContext*
> (change *init (ProcessorContext)* to * init()* ) or
> initiate another KIP before this.
> 
> [1]
> http://cr.openjdk.java.net/~mr/se/8/java-se-8-pfd-spec/java-se-8-jls-pfd-diffs.pdf
> 
> 
> 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi,

Sorry for super late response. Thanks for your comments.

I am not an expert on Lambdas. Can you elaborate a little bit? I cannot
> follow the explanation in the KIP to see what the problem is.


- From [1] says "A functional interface is an interface that has just one
abstract method, and thus represents a single function contract".
So basically once we extend some interface from another (in our case,
ValueMapperWithKey from ValueMapper) we cannot use lambdas in the extended
interface.


Further comments:
>  - The KIP get a little hard to read -- can you maybe reformat the wiki
> page a little bit? I think using `CodeBlock` would help.


- I will work on the KIP.

 - What about KStream-KTable joins? You don't have overlaods added for
> them. Why? (Even if I still hope that we don't need to add any new
> overloads)


- Actually there are more than one Processor and public APIs to be
changed (KStream-KTable
joins is one case). However all of them has similar structure: we overload
the *method* with  *methodWithKey*,
wrap it into the Rich function, send to processor and inside the processor
call *init* and *close* methods of the Rich function.
As I wrote in KIP, I wanted to demonstrate the overall idea with only
*ValueMapper* as the same can be applied to all changes.
Anyway I will update the KIP.

 - Why do we need `AbstractRichFunction`?


Instead of overriding the *init(ProcessorContext p)* and* close()* methods
in every Rich function with empty body like:

@Override
void init(ProcessorContext context) {}

@Override
void close () {}

I thought that we can override them once in *AbstractRichFunction* and
extent new Rich functions from *AbstractRichFunction*.
Basically this can eliminate code copy-paste and ease the maintenance.

 - What about interfaces Initializer, ForeachAction, Merger, Predicate,
> Reducer? I don't want to say we should/need to add to all, but we should
> discuss all of them and add where it does make sense (e.g.,
> RichForachAction does make sense IMHO)


Definitely agree. As I said, the same technique applies to all this
interfaces and I didn't want to explode the KIP, just wanted to give the
overall intuition.
However, I will update the KIP as I said.


Btw: I like the hierarchy `ValueXX` -- `ValueXXWithKey` -- `RichValueXX`
> in general -- but why can't we do all this with interfaces only?


Sure we can. However the main intuition is we should not force users to
implement *init(ProcessorContext)* and *close()* functions every time they
use Rich functions.
If one needs, she can override the respective methods. However, I am open
for discussion.


I'd rather not see the use of  `ProcessorContext` spread any further than
> it currently is. So maybe we need another KIP that is done before this?
> Otherwise i think the scope of this KIP is becoming too large.


That is good point. I wanted to make *init(ProcessorContext)* method
persistent among the library (which use ProcessorContext as an input),
therefore I put *ProcessorContext* as an input.
So the important question is that (as @dguy and @mjsax mentioned) whether
continue this KIP without providing users an access to *ProcessorContext*
(change *init (ProcessorContext)* to * init()* ) or
initiate another KIP before this.

[1]
http://cr.openjdk.java.net/~mr/se/8/java-se-8-pfd-spec/java-se-8-jls-pfd-diffs.pdf


Cheers,
Jeyhun

On Mon, May 15, 2017 at 7:15 PM, Damian Guy  wrote:

> I'd rather not see the use of  `ProcessorContext` spread any further than
> it currently is. So maybe we need another KIP that is done before this?
> Otherwise i think the scope of this KIP is becoming too large.
>
>
> On Mon, 15 May 2017 at 18:06 Matthias J. Sax 
> wrote:
>
> > I agree that that `ProcessorContext` interface is too broad in general
> > -- this is even true for transform/process, and it's also reflected in
> > the API improvement list we want to do.
> >
> > https://cwiki.apache.org/confluence/display/KAFKA/
> Kafka+Streams+Discussions
> >
> > So I am wondering, if you question the `RichFunction` approach in
> > general? Or if you suggest to either extend the scope of this KIP to
> > include this---or maybe better, do another KIP for it and delay this KIP
> > until the other one is done?
> >
> >
> > -Matthias
> >
> > On 5/15/17 2:35 AM, Damian Guy wrote:
> > > Thanks for the KIP.
> > >
> > > I'm not convinced on the `RichFunction` approach. Do we really want to
> > give
> > > every DSL method access to the `ProcessorContext` ? It has a bunch of
> > > methods on it that seem in-appropriate for some of the DSL methods,
> i.e,
> > > `register`, `getStateStore`, `forward`, `schedule` etc. It is far too
> > > broad. I think it would be better to have a narrower interface like the
> > > `RecordContext`  - remembering it is easier to add methods/interfaces
> > later
> > > than to remove them
> > >
> > > On Sat, 13 May 2017 at 22:26 Matthias J. Sax 
> > wrote:
> > >
> > >> 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Damian Guy]

I'd rather not see the use of  `ProcessorContext` spread any further than
it currently is. So maybe we need another KIP that is done before this?
Otherwise i think the scope of this KIP is becoming too large.


On Mon, 15 May 2017 at 18:06 Matthias J. Sax  wrote:

> I agree that that `ProcessorContext` interface is too broad in general
> -- this is even true for transform/process, and it's also reflected in
> the API improvement list we want to do.
>
> https://cwiki.apache.org/confluence/display/KAFKA/Kafka+Streams+Discussions
>
> So I am wondering, if you question the `RichFunction` approach in
> general? Or if you suggest to either extend the scope of this KIP to
> include this---or maybe better, do another KIP for it and delay this KIP
> until the other one is done?
>
>
> -Matthias
>
> On 5/15/17 2:35 AM, Damian Guy wrote:
> > Thanks for the KIP.
> >
> > I'm not convinced on the `RichFunction` approach. Do we really want to
> give
> > every DSL method access to the `ProcessorContext` ? It has a bunch of
> > methods on it that seem in-appropriate for some of the DSL methods, i.e,
> > `register`, `getStateStore`, `forward`, `schedule` etc. It is far too
> > broad. I think it would be better to have a narrower interface like the
> > `RecordContext`  - remembering it is easier to add methods/interfaces
> later
> > than to remove them
> >
> > On Sat, 13 May 2017 at 22:26 Matthias J. Sax 
> wrote:
> >
> >> Jeyhun,
> >>
> >> I am not an expert on Lambdas. Can you elaborate a little bit? I cannot
> >> follow the explanation in the KIP to see what the problem is.
> >>
> >> For updating the KIP title I don't know -- guess it's up to you. Maybe a
> >> committer can comment on this?
> >>
> >>
> >> Further comments:
> >>
> >>  - The KIP get a little hard to read -- can you maybe reformat the wiki
> >> page a little bit? I think using `CodeBlock` would help.
> >>
> >>  - What about KStream-KTable joins? You don't have overlaods added for
> >> them. Why? (Even if I still hope that we don't need to add any new
> >> overloads)
> >>
> >>  - Why do we need `AbstractRichFunction`?
> >>
> >>  - What about interfaces Initializer, ForeachAction, Merger, Predicate,
> >> Reducer? I don't want to say we should/need to add to all, but we should
> >> discuss all of them and add where it does make sense (e.g.,
> >> RichForachAction does make sense IMHO)
> >>
> >>
> >> Btw: I like the hierarchy `ValueXX` -- `ValueXXWithKey` -- `RichValueXX`
> >> in general -- but why can't we do all this with interfaces only?
> >>
> >>
> >>
> >> -Matthias
> >>
> >>
> >>
> >> On 5/11/17 7:00 AM, Jeyhun Karimov wrote:
> >>> Hi,
> >>>
> >>> Thanks for your comments. I think we cannot extend the two interfaces
> if
> >> we
> >>> want to keep lambdas. I updated the KIP [1]. Maybe I should change the
> >>> title, because now we are not limiting the KIP to only ValueMapper,
> >>> ValueTransformer and ValueJoiner.
> >>> Please feel free to comment.
> >>>
> >>> [1]
> >>>
> >>
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-149%3A+Enabling+key+access+in+ValueTransformer%2C+ValueMapper%2C+and+ValueJoiner
> >>>
> >>>
> >>> Cheers,
> >>> Jeyhun
> >>>
> >>> On Tue, May 9, 2017 at 7:36 PM Matthias J. Sax 
> >>> wrote:
> >>>
>  If `ValueMapperWithKey` extends `ValueMapper` we don't need the new
>  overlaod.
> 
>  And yes, we need to do one check -- but this happens when building the
>  topology. At runtime (I mean after KafkaStream#start() we don't need
> any
>  check as we will always use `ValueMapperWithKey`)
> 
> 
>  -Matthias
> 
> 
>  On 5/9/17 2:55 AM, Jeyhun Karimov wrote:
> > Hi,
> >
> > Thanks for feedback.
> > Then we need to overload method
> >KStream mapValues(ValueMapper
> > mapper);
> > with
> >KStream mapValues(ValueMapperWithKey extends
>  VR>
> > mapper);
> >
> > and in runtime (inside processor) we still have to check it is
>  ValueMapper
> > or ValueMapperWithKey before wrapping it into the rich function.
> >
> >
> > Please correct me if I am wrong.
> >
> > Cheers,
> > Jeyhun
> >
> >
> >
> >
> > On Tue, May 9, 2017 at 10:56 AM Michal Borowiecki <
> > michal.borowie...@openbet.com> wrote:
> >
> >> +1 :)
> >>
> >>
> >> On 08/05/17 23:52, Matthias J. Sax wrote:
> >>> Hi,
> >>>
> >>> I was reading the updated KIP and I am wondering, if we should do
> the
> >>> design a little different.
> >>>
> >>> Instead of distinguishing between a RichFunction and
> non-RichFunction
>  at
> >>> runtime level, we would use RichFunctions all the time. Thus, on
> the
>  DSL
> >>> entry level, if a user provides a non-RichFunction, we wrap it by a
> >>> RichFunction that is fully implemented by Streams. This
> RichFunction
> >>> would just forward the 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

I agree that that `ProcessorContext` interface is too broad in general
-- this is even true for transform/process, and it's also reflected in
the API improvement list we want to do.

https://cwiki.apache.org/confluence/display/KAFKA/Kafka+Streams+Discussions

So I am wondering, if you question the `RichFunction` approach in
general? Or if you suggest to either extend the scope of this KIP to
include this---or maybe better, do another KIP for it and delay this KIP
until the other one is done?


-Matthias

On 5/15/17 2:35 AM, Damian Guy wrote:
> Thanks for the KIP.
> 
> I'm not convinced on the `RichFunction` approach. Do we really want to give
> every DSL method access to the `ProcessorContext` ? It has a bunch of
> methods on it that seem in-appropriate for some of the DSL methods, i.e,
> `register`, `getStateStore`, `forward`, `schedule` etc. It is far too
> broad. I think it would be better to have a narrower interface like the
> `RecordContext`  - remembering it is easier to add methods/interfaces later
> than to remove them
> 
> On Sat, 13 May 2017 at 22:26 Matthias J. Sax  wrote:
> 
>> Jeyhun,
>>
>> I am not an expert on Lambdas. Can you elaborate a little bit? I cannot
>> follow the explanation in the KIP to see what the problem is.
>>
>> For updating the KIP title I don't know -- guess it's up to you. Maybe a
>> committer can comment on this?
>>
>>
>> Further comments:
>>
>>  - The KIP get a little hard to read -- can you maybe reformat the wiki
>> page a little bit? I think using `CodeBlock` would help.
>>
>>  - What about KStream-KTable joins? You don't have overlaods added for
>> them. Why? (Even if I still hope that we don't need to add any new
>> overloads)
>>
>>  - Why do we need `AbstractRichFunction`?
>>
>>  - What about interfaces Initializer, ForeachAction, Merger, Predicate,
>> Reducer? I don't want to say we should/need to add to all, but we should
>> discuss all of them and add where it does make sense (e.g.,
>> RichForachAction does make sense IMHO)
>>
>>
>> Btw: I like the hierarchy `ValueXX` -- `ValueXXWithKey` -- `RichValueXX`
>> in general -- but why can't we do all this with interfaces only?
>>
>>
>>
>> -Matthias
>>
>>
>>
>> On 5/11/17 7:00 AM, Jeyhun Karimov wrote:
>>> Hi,
>>>
>>> Thanks for your comments. I think we cannot extend the two interfaces if
>> we
>>> want to keep lambdas. I updated the KIP [1]. Maybe I should change the
>>> title, because now we are not limiting the KIP to only ValueMapper,
>>> ValueTransformer and ValueJoiner.
>>> Please feel free to comment.
>>>
>>> [1]
>>>
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-149%3A+Enabling+key+access+in+ValueTransformer%2C+ValueMapper%2C+and+ValueJoiner
>>>
>>>
>>> Cheers,
>>> Jeyhun
>>>
>>> On Tue, May 9, 2017 at 7:36 PM Matthias J. Sax 
>>> wrote:
>>>
 If `ValueMapperWithKey` extends `ValueMapper` we don't need the new
 overlaod.

 And yes, we need to do one check -- but this happens when building the
 topology. At runtime (I mean after KafkaStream#start() we don't need any
 check as we will always use `ValueMapperWithKey`)


 -Matthias


 On 5/9/17 2:55 AM, Jeyhun Karimov wrote:
> Hi,
>
> Thanks for feedback.
> Then we need to overload method
>KStream mapValues(ValueMapper
> mapper);
> with
>KStream mapValues(ValueMapperWithKey>>> VR>
> mapper);
>
> and in runtime (inside processor) we still have to check it is
 ValueMapper
> or ValueMapperWithKey before wrapping it into the rich function.
>
>
> Please correct me if I am wrong.
>
> Cheers,
> Jeyhun
>
>
>
>
> On Tue, May 9, 2017 at 10:56 AM Michal Borowiecki <
> michal.borowie...@openbet.com> wrote:
>
>> +1 :)
>>
>>
>> On 08/05/17 23:52, Matthias J. Sax wrote:
>>> Hi,
>>>
>>> I was reading the updated KIP and I am wondering, if we should do the
>>> design a little different.
>>>
>>> Instead of distinguishing between a RichFunction and non-RichFunction
 at
>>> runtime level, we would use RichFunctions all the time. Thus, on the
 DSL
>>> entry level, if a user provides a non-RichFunction, we wrap it by a
>>> RichFunction that is fully implemented by Streams. This RichFunction
>>> would just forward the call omitting the key:
>>>
>>> Just to sketch the idea (incomplete code snippet):
>>>
 public StreamsRichValueMapper implements RichValueMapper() {
private ValueMapper userProvidedMapper; // set by constructor

public VR apply(final K key, final V1 value1, final V2 value2) {
return userProvidedMapper(value1, value2);
}
 }
>>>
>>>  From a performance point of view, I am not sure if the
>>> "if(isRichFunction)" including casts etc would have more overhead
>> than
>>> this approach 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Damian Guy]

Thanks for the KIP.

I'm not convinced on the `RichFunction` approach. Do we really want to give
every DSL method access to the `ProcessorContext` ? It has a bunch of
methods on it that seem in-appropriate for some of the DSL methods, i.e,
`register`, `getStateStore`, `forward`, `schedule` etc. It is far too
broad. I think it would be better to have a narrower interface like the
`RecordContext`  - remembering it is easier to add methods/interfaces later
than to remove them

On Sat, 13 May 2017 at 22:26 Matthias J. Sax  wrote:

> Jeyhun,
>
> I am not an expert on Lambdas. Can you elaborate a little bit? I cannot
> follow the explanation in the KIP to see what the problem is.
>
> For updating the KIP title I don't know -- guess it's up to you. Maybe a
> committer can comment on this?
>
>
> Further comments:
>
>  - The KIP get a little hard to read -- can you maybe reformat the wiki
> page a little bit? I think using `CodeBlock` would help.
>
>  - What about KStream-KTable joins? You don't have overlaods added for
> them. Why? (Even if I still hope that we don't need to add any new
> overloads)
>
>  - Why do we need `AbstractRichFunction`?
>
>  - What about interfaces Initializer, ForeachAction, Merger, Predicate,
> Reducer? I don't want to say we should/need to add to all, but we should
> discuss all of them and add where it does make sense (e.g.,
> RichForachAction does make sense IMHO)
>
>
> Btw: I like the hierarchy `ValueXX` -- `ValueXXWithKey` -- `RichValueXX`
> in general -- but why can't we do all this with interfaces only?
>
>
>
> -Matthias
>
>
>
> On 5/11/17 7:00 AM, Jeyhun Karimov wrote:
> > Hi,
> >
> > Thanks for your comments. I think we cannot extend the two interfaces if
> we
> > want to keep lambdas. I updated the KIP [1]. Maybe I should change the
> > title, because now we are not limiting the KIP to only ValueMapper,
> > ValueTransformer and ValueJoiner.
> > Please feel free to comment.
> >
> > [1]
> >
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-149%3A+Enabling+key+access+in+ValueTransformer%2C+ValueMapper%2C+and+ValueJoiner
> >
> >
> > Cheers,
> > Jeyhun
> >
> > On Tue, May 9, 2017 at 7:36 PM Matthias J. Sax 
> > wrote:
> >
> >> If `ValueMapperWithKey` extends `ValueMapper` we don't need the new
> >> overlaod.
> >>
> >> And yes, we need to do one check -- but this happens when building the
> >> topology. At runtime (I mean after KafkaStream#start() we don't need any
> >> check as we will always use `ValueMapperWithKey`)
> >>
> >>
> >> -Matthias
> >>
> >>
> >> On 5/9/17 2:55 AM, Jeyhun Karimov wrote:
> >>> Hi,
> >>>
> >>> Thanks for feedback.
> >>> Then we need to overload method
> >>>KStream mapValues(ValueMapper
> >>> mapper);
> >>> with
> >>>KStream mapValues(ValueMapperWithKey >> VR>
> >>> mapper);
> >>>
> >>> and in runtime (inside processor) we still have to check it is
> >> ValueMapper
> >>> or ValueMapperWithKey before wrapping it into the rich function.
> >>>
> >>>
> >>> Please correct me if I am wrong.
> >>>
> >>> Cheers,
> >>> Jeyhun
> >>>
> >>>
> >>>
> >>>
> >>> On Tue, May 9, 2017 at 10:56 AM Michal Borowiecki <
> >>> michal.borowie...@openbet.com> wrote:
> >>>
>  +1 :)
> 
> 
>  On 08/05/17 23:52, Matthias J. Sax wrote:
> > Hi,
> >
> > I was reading the updated KIP and I am wondering, if we should do the
> > design a little different.
> >
> > Instead of distinguishing between a RichFunction and non-RichFunction
> >> at
> > runtime level, we would use RichFunctions all the time. Thus, on the
> >> DSL
> > entry level, if a user provides a non-RichFunction, we wrap it by a
> > RichFunction that is fully implemented by Streams. This RichFunction
> > would just forward the call omitting the key:
> >
> > Just to sketch the idea (incomplete code snippet):
> >
> >> public StreamsRichValueMapper implements RichValueMapper() {
> >>private ValueMapper userProvidedMapper; // set by constructor
> >>
> >>public VR apply(final K key, final V1 value1, final V2 value2) {
> >>return userProvidedMapper(value1, value2);
> >>}
> >> }
> >
> >  From a performance point of view, I am not sure if the
> > "if(isRichFunction)" including casts etc would have more overhead
> than
> > this approach (we would do more nested method call for
> non-RichFunction
> > which should be more common than RichFunctions).
> >
> > This approach should not effect lambdas (or do I miss something?) and
> > might be cleaner, as we could have one more top level interface
> > `RichFunction` with methods `init()` and `close()` and also
> interfaces
> > for `RichValueMapper` etc. (thus, no abstract classes required).
> >
> >
> > Any thoughts?
> >
> >
> > -Matthias
> >
> >
> > On 5/6/17 5:29 PM, Jeyhun Karimov wrote:
> >> Hi,
> >>
> >> Thanks for 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Jeyhun,

I am not an expert on Lambdas. Can you elaborate a little bit? I cannot
follow the explanation in the KIP to see what the problem is.

For updating the KIP title I don't know -- guess it's up to you. Maybe a
committer can comment on this?


Further comments:

 - The KIP get a little hard to read -- can you maybe reformat the wiki
page a little bit? I think using `CodeBlock` would help.

 - What about KStream-KTable joins? You don't have overlaods added for
them. Why? (Even if I still hope that we don't need to add any new
overloads)

 - Why do we need `AbstractRichFunction`?

 - What about interfaces Initializer, ForeachAction, Merger, Predicate,
Reducer? I don't want to say we should/need to add to all, but we should
discuss all of them and add where it does make sense (e.g.,
RichForachAction does make sense IMHO)


Btw: I like the hierarchy `ValueXX` -- `ValueXXWithKey` -- `RichValueXX`
in general -- but why can't we do all this with interfaces only?



-Matthias



On 5/11/17 7:00 AM, Jeyhun Karimov wrote:
> Hi,
> 
> Thanks for your comments. I think we cannot extend the two interfaces if we
> want to keep lambdas. I updated the KIP [1]. Maybe I should change the
> title, because now we are not limiting the KIP to only ValueMapper,
> ValueTransformer and ValueJoiner.
> Please feel free to comment.
> 
> [1]
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-149%3A+Enabling+key+access+in+ValueTransformer%2C+ValueMapper%2C+and+ValueJoiner
> 
> 
> Cheers,
> Jeyhun
> 
> On Tue, May 9, 2017 at 7:36 PM Matthias J. Sax 
> wrote:
> 
>> If `ValueMapperWithKey` extends `ValueMapper` we don't need the new
>> overlaod.
>>
>> And yes, we need to do one check -- but this happens when building the
>> topology. At runtime (I mean after KafkaStream#start() we don't need any
>> check as we will always use `ValueMapperWithKey`)
>>
>>
>> -Matthias
>>
>>
>> On 5/9/17 2:55 AM, Jeyhun Karimov wrote:
>>> Hi,
>>>
>>> Thanks for feedback.
>>> Then we need to overload method
>>>KStream mapValues(ValueMapper
>>> mapper);
>>> with
>>>KStream mapValues(ValueMapperWithKey> VR>
>>> mapper);
>>>
>>> and in runtime (inside processor) we still have to check it is
>> ValueMapper
>>> or ValueMapperWithKey before wrapping it into the rich function.
>>>
>>>
>>> Please correct me if I am wrong.
>>>
>>> Cheers,
>>> Jeyhun
>>>
>>>
>>>
>>>
>>> On Tue, May 9, 2017 at 10:56 AM Michal Borowiecki <
>>> michal.borowie...@openbet.com> wrote:
>>>
 +1 :)


 On 08/05/17 23:52, Matthias J. Sax wrote:
> Hi,
>
> I was reading the updated KIP and I am wondering, if we should do the
> design a little different.
>
> Instead of distinguishing between a RichFunction and non-RichFunction
>> at
> runtime level, we would use RichFunctions all the time. Thus, on the
>> DSL
> entry level, if a user provides a non-RichFunction, we wrap it by a
> RichFunction that is fully implemented by Streams. This RichFunction
> would just forward the call omitting the key:
>
> Just to sketch the idea (incomplete code snippet):
>
>> public StreamsRichValueMapper implements RichValueMapper() {
>>private ValueMapper userProvidedMapper; // set by constructor
>>
>>public VR apply(final K key, final V1 value1, final V2 value2) {
>>return userProvidedMapper(value1, value2);
>>}
>> }
>
>  From a performance point of view, I am not sure if the
> "if(isRichFunction)" including casts etc would have more overhead than
> this approach (we would do more nested method call for non-RichFunction
> which should be more common than RichFunctions).
>
> This approach should not effect lambdas (or do I miss something?) and
> might be cleaner, as we could have one more top level interface
> `RichFunction` with methods `init()` and `close()` and also interfaces
> for `RichValueMapper` etc. (thus, no abstract classes required).
>
>
> Any thoughts?
>
>
> -Matthias
>
>
> On 5/6/17 5:29 PM, Jeyhun Karimov wrote:
>> Hi,
>>
>> Thanks for comments. I extended PR and KIP to include rich functions.
>> I
>> will still have to evaluate the cost of deep copying of keys.
>>
>> Cheers,
>> Jeyhun
>>
>> On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak <
 mathieu.fenn...@replicon.com>
>> wrote:
>>
>>> Hey Matthias,
>>>
>>> My opinion would be that documenting the immutability of the key is
>> the
>>> best approach available.  Better than requiring the key to be
 serializable
>>> (as with Jeyhun's last pass at the PR), no performance risk.
>>>
>>> It'd be different if Java had immutable type constraints of some
>> kind.
 :-)
>>>
>>> Mathieu
>>>
>>>
>>> On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax <
 matth...@confluent.io>
>>> wrote:
>>>
 Agreed about 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi,

Thanks for your comments. I think we cannot extend the two interfaces if we
want to keep lambdas. I updated the KIP [1]. Maybe I should change the
title, because now we are not limiting the KIP to only ValueMapper,
ValueTransformer and ValueJoiner.
Please feel free to comment.

[1]
https://cwiki.apache.org/confluence/display/KAFKA/KIP-149%3A+Enabling+key+access+in+ValueTransformer%2C+ValueMapper%2C+and+ValueJoiner


Cheers,
Jeyhun

On Tue, May 9, 2017 at 7:36 PM Matthias J. Sax 
wrote:

> If `ValueMapperWithKey` extends `ValueMapper` we don't need the new
> overlaod.
>
> And yes, we need to do one check -- but this happens when building the
> topology. At runtime (I mean after KafkaStream#start() we don't need any
> check as we will always use `ValueMapperWithKey`)
>
>
> -Matthias
>
>
> On 5/9/17 2:55 AM, Jeyhun Karimov wrote:
> > Hi,
> >
> > Thanks for feedback.
> > Then we need to overload method
> >KStream mapValues(ValueMapper
> > mapper);
> > with
> >KStream mapValues(ValueMapperWithKey VR>
> > mapper);
> >
> > and in runtime (inside processor) we still have to check it is
> ValueMapper
> > or ValueMapperWithKey before wrapping it into the rich function.
> >
> >
> > Please correct me if I am wrong.
> >
> > Cheers,
> > Jeyhun
> >
> >
> >
> >
> > On Tue, May 9, 2017 at 10:56 AM Michal Borowiecki <
> > michal.borowie...@openbet.com> wrote:
> >
> >> +1 :)
> >>
> >>
> >> On 08/05/17 23:52, Matthias J. Sax wrote:
> >>> Hi,
> >>>
> >>> I was reading the updated KIP and I am wondering, if we should do the
> >>> design a little different.
> >>>
> >>> Instead of distinguishing between a RichFunction and non-RichFunction
> at
> >>> runtime level, we would use RichFunctions all the time. Thus, on the
> DSL
> >>> entry level, if a user provides a non-RichFunction, we wrap it by a
> >>> RichFunction that is fully implemented by Streams. This RichFunction
> >>> would just forward the call omitting the key:
> >>>
> >>> Just to sketch the idea (incomplete code snippet):
> >>>
>  public StreamsRichValueMapper implements RichValueMapper() {
> private ValueMapper userProvidedMapper; // set by constructor
> 
> public VR apply(final K key, final V1 value1, final V2 value2) {
> return userProvidedMapper(value1, value2);
> }
>  }
> >>>
> >>>  From a performance point of view, I am not sure if the
> >>> "if(isRichFunction)" including casts etc would have more overhead than
> >>> this approach (we would do more nested method call for non-RichFunction
> >>> which should be more common than RichFunctions).
> >>>
> >>> This approach should not effect lambdas (or do I miss something?) and
> >>> might be cleaner, as we could have one more top level interface
> >>> `RichFunction` with methods `init()` and `close()` and also interfaces
> >>> for `RichValueMapper` etc. (thus, no abstract classes required).
> >>>
> >>>
> >>> Any thoughts?
> >>>
> >>>
> >>> -Matthias
> >>>
> >>>
> >>> On 5/6/17 5:29 PM, Jeyhun Karimov wrote:
>  Hi,
> 
>  Thanks for comments. I extended PR and KIP to include rich functions.
> I
>  will still have to evaluate the cost of deep copying of keys.
> 
>  Cheers,
>  Jeyhun
> 
>  On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak <
> >> mathieu.fenn...@replicon.com>
>  wrote:
> 
> > Hey Matthias,
> >
> > My opinion would be that documenting the immutability of the key is
> the
> > best approach available.  Better than requiring the key to be
> >> serializable
> > (as with Jeyhun's last pass at the PR), no performance risk.
> >
> > It'd be different if Java had immutable type constraints of some
> kind.
> >> :-)
> >
> > Mathieu
> >
> >
> > On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax <
> >> matth...@confluent.io>
> > wrote:
> >
> >> Agreed about RichFunction. If we follow this path, it should cover
> >> all(?) DSL interfaces.
> >>
> >> About guarding the key -- I am still not sure what to do about it...
> >> Maybe it might be enough to document it (and name the key parameter
> >> like
> >> `readOnlyKey` to make is very clear). Ultimately, I would prefer to
> >> guard against any modification, but I have no good idea how to do
> >> this.
> >> Not sure what others think about the risk of corrupted partitioning
> >> (what would be a user error and we could say, well, bad luck, you
> got
> >> a
> >> bug in your code, that's not our fault), vs deep copy with a
> potential
> >> performance hit (that we can't quantity atm without any performance
> > test).
> >> We do have a performance system test. Maybe it's worth for you to
> >> apply
> >> the deep copy strategy and run the test. It's very basic performance
> >> test only, but might give some insight. If you want to do this, look
> >> into folder "tests" for general test setup, and into
> >> 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

If `ValueMapperWithKey` extends `ValueMapper` we don't need the new
overlaod.

And yes, we need to do one check -- but this happens when building the
topology. At runtime (I mean after KafkaStream#start() we don't need any
check as we will always use `ValueMapperWithKey`)


-Matthias


On 5/9/17 2:55 AM, Jeyhun Karimov wrote:
> Hi,
> 
> Thanks for feedback.
> Then we need to overload method
>KStream mapValues(ValueMapper
> mapper);
> with
>KStream mapValues(ValueMapperWithKey
> mapper);
> 
> and in runtime (inside processor) we still have to check it is ValueMapper
> or ValueMapperWithKey before wrapping it into the rich function.
> 
> 
> Please correct me if I am wrong.
> 
> Cheers,
> Jeyhun
> 
> 
> 
> 
> On Tue, May 9, 2017 at 10:56 AM Michal Borowiecki <
> michal.borowie...@openbet.com> wrote:
> 
>> +1 :)
>>
>>
>> On 08/05/17 23:52, Matthias J. Sax wrote:
>>> Hi,
>>>
>>> I was reading the updated KIP and I am wondering, if we should do the
>>> design a little different.
>>>
>>> Instead of distinguishing between a RichFunction and non-RichFunction at
>>> runtime level, we would use RichFunctions all the time. Thus, on the DSL
>>> entry level, if a user provides a non-RichFunction, we wrap it by a
>>> RichFunction that is fully implemented by Streams. This RichFunction
>>> would just forward the call omitting the key:
>>>
>>> Just to sketch the idea (incomplete code snippet):
>>>
 public StreamsRichValueMapper implements RichValueMapper() {
private ValueMapper userProvidedMapper; // set by constructor

public VR apply(final K key, final V1 value1, final V2 value2) {
return userProvidedMapper(value1, value2);
}
 }
>>>
>>>  From a performance point of view, I am not sure if the
>>> "if(isRichFunction)" including casts etc would have more overhead than
>>> this approach (we would do more nested method call for non-RichFunction
>>> which should be more common than RichFunctions).
>>>
>>> This approach should not effect lambdas (or do I miss something?) and
>>> might be cleaner, as we could have one more top level interface
>>> `RichFunction` with methods `init()` and `close()` and also interfaces
>>> for `RichValueMapper` etc. (thus, no abstract classes required).
>>>
>>>
>>> Any thoughts?
>>>
>>>
>>> -Matthias
>>>
>>>
>>> On 5/6/17 5:29 PM, Jeyhun Karimov wrote:
 Hi,

 Thanks for comments. I extended PR and KIP to include rich functions. I
 will still have to evaluate the cost of deep copying of keys.

 Cheers,
 Jeyhun

 On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak <
>> mathieu.fenn...@replicon.com>
 wrote:

> Hey Matthias,
>
> My opinion would be that documenting the immutability of the key is the
> best approach available.  Better than requiring the key to be
>> serializable
> (as with Jeyhun's last pass at the PR), no performance risk.
>
> It'd be different if Java had immutable type constraints of some kind.
>> :-)
>
> Mathieu
>
>
> On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax <
>> matth...@confluent.io>
> wrote:
>
>> Agreed about RichFunction. If we follow this path, it should cover
>> all(?) DSL interfaces.
>>
>> About guarding the key -- I am still not sure what to do about it...
>> Maybe it might be enough to document it (and name the key parameter
>> like
>> `readOnlyKey` to make is very clear). Ultimately, I would prefer to
>> guard against any modification, but I have no good idea how to do
>> this.
>> Not sure what others think about the risk of corrupted partitioning
>> (what would be a user error and we could say, well, bad luck, you got
>> a
>> bug in your code, that's not our fault), vs deep copy with a potential
>> performance hit (that we can't quantity atm without any performance
> test).
>> We do have a performance system test. Maybe it's worth for you to
>> apply
>> the deep copy strategy and run the test. It's very basic performance
>> test only, but might give some insight. If you want to do this, look
>> into folder "tests" for general test setup, and into
>> "tests/kafaktests/benchmarks/streams" to find find the perf test.
>>
>>
>> -Matthias
>>
>> On 5/5/17 8:55 AM, Jeyhun Karimov wrote:
>>> Hi Matthias,
>>>
>>> I think extending KIP to include RichFunctions totally  makes sense.
> So,
>>>   we don't want to guard the keys because it is costly.
>>> If we introduce RichFunctions I think it should not be limited only
> the 3
>>> interfaces proposed in KIP but to wide range of interfaces.
>>> Please correct me if I am wrong.
>>>
>>> Cheers,
>>> Jeyhun
>>>
>>> On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax <
>> matth...@confluent.io
>>> wrote:
>>>
 One follow up. There was this email on the user list:


 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

One correction:


and in runtime (inside processor) we still have to check it is ValueMapper
> or ValueMapperWithKey before wrapping it into the rich function.


this will be in compile time in API level.



Cheers,
Jeyhun


On Tue, May 9, 2017 at 11:55 AM Jeyhun Karimov  wrote:

> Hi,
>
> Thanks for feedback.
> Then we need to overload method
>KStream mapValues(ValueMapper
> mapper);
> with
>KStream mapValues(ValueMapperWithKey VR> mapper);
>
> and in runtime (inside processor) we still have to check it is ValueMapper
> or ValueMapperWithKey before wrapping it into the rich function.
>
>
> Please correct me if I am wrong.
>
> Cheers,
> Jeyhun
>
>
>
>
> On Tue, May 9, 2017 at 10:56 AM Michal Borowiecki <
> michal.borowie...@openbet.com> wrote:
>
>> +1 :)
>>
>>
>> On 08/05/17 23:52, Matthias J. Sax wrote:
>> > Hi,
>> >
>> > I was reading the updated KIP and I am wondering, if we should do the
>> > design a little different.
>> >
>> > Instead of distinguishing between a RichFunction and non-RichFunction at
>> > runtime level, we would use RichFunctions all the time. Thus, on the DSL
>> > entry level, if a user provides a non-RichFunction, we wrap it by a
>> > RichFunction that is fully implemented by Streams. This RichFunction
>> > would just forward the call omitting the key:
>> >
>> > Just to sketch the idea (incomplete code snippet):
>> >
>> >> public StreamsRichValueMapper implements RichValueMapper() {
>> >>private ValueMapper userProvidedMapper; // set by constructor
>> >>
>> >>public VR apply(final K key, final V1 value1, final V2 value2) {
>> >>return userProvidedMapper(value1, value2);
>> >>}
>> >> }
>> >
>> >  From a performance point of view, I am not sure if the
>> > "if(isRichFunction)" including casts etc would have more overhead than
>> > this approach (we would do more nested method call for non-RichFunction
>> > which should be more common than RichFunctions).
>> >
>> > This approach should not effect lambdas (or do I miss something?) and
>> > might be cleaner, as we could have one more top level interface
>> > `RichFunction` with methods `init()` and `close()` and also interfaces
>> > for `RichValueMapper` etc. (thus, no abstract classes required).
>> >
>> >
>> > Any thoughts?
>> >
>> >
>> > -Matthias
>> >
>> >
>> > On 5/6/17 5:29 PM, Jeyhun Karimov wrote:
>> >> Hi,
>> >>
>> >> Thanks for comments. I extended PR and KIP to include rich functions. I
>> >> will still have to evaluate the cost of deep copying of keys.
>> >>
>> >> Cheers,
>> >> Jeyhun
>> >>
>> >> On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak <
>> mathieu.fenn...@replicon.com>
>> >> wrote:
>> >>
>> >>> Hey Matthias,
>> >>>
>> >>> My opinion would be that documenting the immutability of the key is
>> the
>> >>> best approach available.  Better than requiring the key to be
>> serializable
>> >>> (as with Jeyhun's last pass at the PR), no performance risk.
>> >>>
>> >>> It'd be different if Java had immutable type constraints of some
>> kind. :-)
>> >>>
>> >>> Mathieu
>> >>>
>> >>>
>> >>> On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax <
>> matth...@confluent.io>
>> >>> wrote:
>> >>>
>>  Agreed about RichFunction. If we follow this path, it should cover
>>  all(?) DSL interfaces.
>> 
>>  About guarding the key -- I am still not sure what to do about it...
>>  Maybe it might be enough to document it (and name the key parameter
>> like
>>  `readOnlyKey` to make is very clear). Ultimately, I would prefer to
>>  guard against any modification, but I have no good idea how to do
>> this.
>>  Not sure what others think about the risk of corrupted partitioning
>>  (what would be a user error and we could say, well, bad luck, you
>> got a
>>  bug in your code, that's not our fault), vs deep copy with a
>> potential
>>  performance hit (that we can't quantity atm without any performance
>> >>> test).
>>  We do have a performance system test. Maybe it's worth for you to
>> apply
>>  the deep copy strategy and run the test. It's very basic performance
>>  test only, but might give some insight. If you want to do this, look
>>  into folder "tests" for general test setup, and into
>>  "tests/kafaktests/benchmarks/streams" to find find the perf test.
>> 
>> 
>>  -Matthias
>> 
>>  On 5/5/17 8:55 AM, Jeyhun Karimov wrote:
>> > Hi Matthias,
>> >
>> > I think extending KIP to include RichFunctions totally  makes sense.
>> >>> So,
>> >   we don't want to guard the keys because it is costly.
>> > If we introduce RichFunctions I think it should not be limited only
>> >>> the 3
>> > interfaces proposed in KIP but to wide range of interfaces.
>> > Please correct me if I am wrong.
>> >
>> > Cheers,
>> > Jeyhun
>> >
>> > On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax <
>> matth...@confluent.io
>> > wrote:
>> >
>> >> One follow up. There was this 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi,

Thanks for feedback.
Then we need to overload method
   KStream mapValues(ValueMapper
mapper);
with
   KStream mapValues(ValueMapperWithKey
mapper);

and in runtime (inside processor) we still have to check it is ValueMapper
or ValueMapperWithKey before wrapping it into the rich function.


Please correct me if I am wrong.

Cheers,
Jeyhun




On Tue, May 9, 2017 at 10:56 AM Michal Borowiecki <
michal.borowie...@openbet.com> wrote:

> +1 :)
>
>
> On 08/05/17 23:52, Matthias J. Sax wrote:
> > Hi,
> >
> > I was reading the updated KIP and I am wondering, if we should do the
> > design a little different.
> >
> > Instead of distinguishing between a RichFunction and non-RichFunction at
> > runtime level, we would use RichFunctions all the time. Thus, on the DSL
> > entry level, if a user provides a non-RichFunction, we wrap it by a
> > RichFunction that is fully implemented by Streams. This RichFunction
> > would just forward the call omitting the key:
> >
> > Just to sketch the idea (incomplete code snippet):
> >
> >> public StreamsRichValueMapper implements RichValueMapper() {
> >>private ValueMapper userProvidedMapper; // set by constructor
> >>
> >>public VR apply(final K key, final V1 value1, final V2 value2) {
> >>return userProvidedMapper(value1, value2);
> >>}
> >> }
> >
> >  From a performance point of view, I am not sure if the
> > "if(isRichFunction)" including casts etc would have more overhead than
> > this approach (we would do more nested method call for non-RichFunction
> > which should be more common than RichFunctions).
> >
> > This approach should not effect lambdas (or do I miss something?) and
> > might be cleaner, as we could have one more top level interface
> > `RichFunction` with methods `init()` and `close()` and also interfaces
> > for `RichValueMapper` etc. (thus, no abstract classes required).
> >
> >
> > Any thoughts?
> >
> >
> > -Matthias
> >
> >
> > On 5/6/17 5:29 PM, Jeyhun Karimov wrote:
> >> Hi,
> >>
> >> Thanks for comments. I extended PR and KIP to include rich functions. I
> >> will still have to evaluate the cost of deep copying of keys.
> >>
> >> Cheers,
> >> Jeyhun
> >>
> >> On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak <
> mathieu.fenn...@replicon.com>
> >> wrote:
> >>
> >>> Hey Matthias,
> >>>
> >>> My opinion would be that documenting the immutability of the key is the
> >>> best approach available.  Better than requiring the key to be
> serializable
> >>> (as with Jeyhun's last pass at the PR), no performance risk.
> >>>
> >>> It'd be different if Java had immutable type constraints of some kind.
> :-)
> >>>
> >>> Mathieu
> >>>
> >>>
> >>> On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax <
> matth...@confluent.io>
> >>> wrote:
> >>>
>  Agreed about RichFunction. If we follow this path, it should cover
>  all(?) DSL interfaces.
> 
>  About guarding the key -- I am still not sure what to do about it...
>  Maybe it might be enough to document it (and name the key parameter
> like
>  `readOnlyKey` to make is very clear). Ultimately, I would prefer to
>  guard against any modification, but I have no good idea how to do
> this.
>  Not sure what others think about the risk of corrupted partitioning
>  (what would be a user error and we could say, well, bad luck, you got
> a
>  bug in your code, that's not our fault), vs deep copy with a potential
>  performance hit (that we can't quantity atm without any performance
> >>> test).
>  We do have a performance system test. Maybe it's worth for you to
> apply
>  the deep copy strategy and run the test. It's very basic performance
>  test only, but might give some insight. If you want to do this, look
>  into folder "tests" for general test setup, and into
>  "tests/kafaktests/benchmarks/streams" to find find the perf test.
> 
> 
>  -Matthias
> 
>  On 5/5/17 8:55 AM, Jeyhun Karimov wrote:
> > Hi Matthias,
> >
> > I think extending KIP to include RichFunctions totally  makes sense.
> >>> So,
> >   we don't want to guard the keys because it is costly.
> > If we introduce RichFunctions I think it should not be limited only
> >>> the 3
> > interfaces proposed in KIP but to wide range of interfaces.
> > Please correct me if I am wrong.
> >
> > Cheers,
> > Jeyhun
> >
> > On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax <
> matth...@confluent.io
> > wrote:
> >
> >> One follow up. There was this email on the user list:
> >>
> >>
> >> http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=
>  Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+
> >> It might make sense so include Initializer, Adder, and Substractor
> >> inferface, too.
> >>
> >> And we should double check if there are other interface we might
> miss
>  atm.
> >>
> >> -Matthias
> >>
> >>
> >> On 5/4/17 1:31 PM, Matthias J. 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Michal Borowiecki]

+1 :)


On 08/05/17 23:52, Matthias J. Sax wrote:

Hi,

I was reading the updated KIP and I am wondering, if we should do the
design a little different.

Instead of distinguishing between a RichFunction and non-RichFunction at
runtime level, we would use RichFunctions all the time. Thus, on the DSL
entry level, if a user provides a non-RichFunction, we wrap it by a
RichFunction that is fully implemented by Streams. This RichFunction
would just forward the call omitting the key:

Just to sketch the idea (incomplete code snippet):


public StreamsRichValueMapper implements RichValueMapper() {
   private ValueMapper userProvidedMapper; // set by constructor

   public VR apply(final K key, final V1 value1, final V2 value2) {
   return userProvidedMapper(value1, value2);
   }
}


 From a performance point of view, I am not sure if the
"if(isRichFunction)" including casts etc would have more overhead than
this approach (we would do more nested method call for non-RichFunction
which should be more common than RichFunctions).

This approach should not effect lambdas (or do I miss something?) and
might be cleaner, as we could have one more top level interface
`RichFunction` with methods `init()` and `close()` and also interfaces
for `RichValueMapper` etc. (thus, no abstract classes required).


Any thoughts?


-Matthias


On 5/6/17 5:29 PM, Jeyhun Karimov wrote:

Hi,

Thanks for comments. I extended PR and KIP to include rich functions. I
will still have to evaluate the cost of deep copying of keys.

Cheers,
Jeyhun

On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak 
wrote:


Hey Matthias,

My opinion would be that documenting the immutability of the key is the
best approach available.  Better than requiring the key to be serializable
(as with Jeyhun's last pass at the PR), no performance risk.

It'd be different if Java had immutable type constraints of some kind. :-)

Mathieu


On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax 
wrote:


Agreed about RichFunction. If we follow this path, it should cover
all(?) DSL interfaces.

About guarding the key -- I am still not sure what to do about it...
Maybe it might be enough to document it (and name the key parameter like
`readOnlyKey` to make is very clear). Ultimately, I would prefer to
guard against any modification, but I have no good idea how to do this.
Not sure what others think about the risk of corrupted partitioning
(what would be a user error and we could say, well, bad luck, you got a
bug in your code, that's not our fault), vs deep copy with a potential
performance hit (that we can't quantity atm without any performance

test).

We do have a performance system test. Maybe it's worth for you to apply
the deep copy strategy and run the test. It's very basic performance
test only, but might give some insight. If you want to do this, look
into folder "tests" for general test setup, and into
"tests/kafaktests/benchmarks/streams" to find find the perf test.


-Matthias

On 5/5/17 8:55 AM, Jeyhun Karimov wrote:

Hi Matthias,

I think extending KIP to include RichFunctions totally  makes sense.

So,

  we don't want to guard the keys because it is costly.
If we introduce RichFunctions I think it should not be limited only

the 3

interfaces proposed in KIP but to wide range of interfaces.
Please correct me if I am wrong.

Cheers,
Jeyhun

On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax 

wrote:


Hi Jeyhun,

This approach would change ValueMapper (...etc) to be classes,

rather

than

interfaces, which is also a backwards incompatible change.  An

alternative

approach that would be backwards 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Hi,

I was reading the updated KIP and I am wondering, if we should do the
design a little different.

Instead of distinguishing between a RichFunction and non-RichFunction at
runtime level, we would use RichFunctions all the time. Thus, on the DSL
entry level, if a user provides a non-RichFunction, we wrap it by a
RichFunction that is fully implemented by Streams. This RichFunction
would just forward the call omitting the key:

Just to sketch the idea (incomplete code snippet):

> public StreamsRichValueMapper implements RichValueMapper() {
>   private ValueMapper userProvidedMapper; // set by constructor
> 
>   public VR apply(final K key, final V1 value1, final V2 value2) {
>   return userProvidedMapper(value1, value2);
>   }
> }


From a performance point of view, I am not sure if the
"if(isRichFunction)" including casts etc would have more overhead than
this approach (we would do more nested method call for non-RichFunction
which should be more common than RichFunctions).

This approach should not effect lambdas (or do I miss something?) and
might be cleaner, as we could have one more top level interface
`RichFunction` with methods `init()` and `close()` and also interfaces
for `RichValueMapper` etc. (thus, no abstract classes required).


Any thoughts?


-Matthias


On 5/6/17 5:29 PM, Jeyhun Karimov wrote:
> Hi,
> 
> Thanks for comments. I extended PR and KIP to include rich functions. I
> will still have to evaluate the cost of deep copying of keys.
> 
> Cheers,
> Jeyhun
> 
> On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak 
> wrote:
> 
>> Hey Matthias,
>>
>> My opinion would be that documenting the immutability of the key is the
>> best approach available.  Better than requiring the key to be serializable
>> (as with Jeyhun's last pass at the PR), no performance risk.
>>
>> It'd be different if Java had immutable type constraints of some kind. :-)
>>
>> Mathieu
>>
>>
>> On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax 
>> wrote:
>>
>>> Agreed about RichFunction. If we follow this path, it should cover
>>> all(?) DSL interfaces.
>>>
>>> About guarding the key -- I am still not sure what to do about it...
>>> Maybe it might be enough to document it (and name the key parameter like
>>> `readOnlyKey` to make is very clear). Ultimately, I would prefer to
>>> guard against any modification, but I have no good idea how to do this.
>>> Not sure what others think about the risk of corrupted partitioning
>>> (what would be a user error and we could say, well, bad luck, you got a
>>> bug in your code, that's not our fault), vs deep copy with a potential
>>> performance hit (that we can't quantity atm without any performance
>> test).
>>>
>>> We do have a performance system test. Maybe it's worth for you to apply
>>> the deep copy strategy and run the test. It's very basic performance
>>> test only, but might give some insight. If you want to do this, look
>>> into folder "tests" for general test setup, and into
>>> "tests/kafaktests/benchmarks/streams" to find find the perf test.
>>>
>>>
>>> -Matthias
>>>
>>> On 5/5/17 8:55 AM, Jeyhun Karimov wrote:
 Hi Matthias,

 I think extending KIP to include RichFunctions totally  makes sense.
>> So,
  we don't want to guard the keys because it is costly.
 If we introduce RichFunctions I think it should not be limited only
>> the 3
 interfaces proposed in KIP but to wide range of interfaces.
 Please correct me if I am wrong.

 Cheers,
 Jeyhun

 On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax >>
 wrote:

> One follow up. There was this email on the user list:
>
>
> http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=
>>> Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+
>
> It might make sense so include Initializer, Adder, and Substractor
> inferface, too.
>
> And we should double check if there are other interface we might miss
>>> atm.
>
>
> -Matthias
>
>
> On 5/4/17 1:31 PM, Matthias J. Sax wrote:
>> Thanks for updating the KIP.
>>
>> Deep copying the key will work for sure, but I am actually a little
>> bit
>> worried about performance impact... We might want to do some test to
>> quantify this impact.
>>
>>
>> Btw: this remind me about the idea of `RichFunction` interface that
>> would allow users to access record metadata (like timestamp, offset,
>> partition etc) within DSL. This would be a similar concept. Thus, I
>> am
>> wondering, if it would make sense to enlarge the scope of this KIP by
>> that? WDYT?
>>
>>
>>
>> -Matthias
>>
>>
>> On 5/3/17 2:08 AM, Jeyhun Karimov wrote:
>>> Hi Mathieu,
>>>
>>> Thanks for feedback. I followed similar approach and updated PR and
>>> KIP
>>> accordingly. I tried to guard the key in Processors sending a copy
>> of
>>> an

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Michal,

thanks a lot for this comment. I did not consider lambdas when proposing
RichFunctions. I thinks it very important to preserve the ability to use
lambdas!

@Jeyhun: I did not put any thought into this, but can we have a design
that allows for both? Also, with regard to lambdas, it might make sense
to allow for both `V -> newV` and `(K, V) -> newV` ?


-Matthias


On 5/7/17 5:34 AM, Michal Borowiecki wrote:
> Hi Jeyhun,
> 
> Thanks for your quick reply.
> 
> Indeed, I understand the existing ValueMapper/Joiner etc. have to remain
> as-is for backwards compatibility.
> 
> I was just expressing my surprise that their proposed richer equivalents
> weren't functional interfaces too.
> 
> Thanks,
> 
> Michał
> 
> 
> On 07/05/17 12:32, Jeyhun Karimov wrote:
>> Hi Michal,
>>
>> Thanks for your comments. We proposed the similar solution to yours in
>> KIP (please look at rejected alternatives). However, after the
>> discussion in mailing list I extended it to rich functions. Maybe we
>> should keep them both: simple and rich versions.
>>
>> Cheers,
>> Jeyhun
>>
>> On Sun, May 7, 2017 at 11:46 AM Michal Borowiecki
>> >
>> wrote:
>>
>> Do I understanding correctly, that with the proposed pattern one
>> could not pass a lambda expression and access the context from
>> within it?
>>
>> TBH, I was hoping that for simple things this would be possible:
>>
>> myStream.map( (key, value, ctx) -> new KeyValue<>(ctx.partition(),
>> value) )
>>
>> or (more to the original point of this KIP):
>>
>> myStream.mapValues( (key, value, ctx) -> new MyValueWrapper(value,
>> ctx.partition(), ctx.offset()) )
>>
>> but it looks like that would require subclassing RichFunction?
>> That's a bit of an inconvenience IMO.
>>
>> Cheers,
>>
>> Michal
>>
>>
>> On 07/05/17 01:29, Jeyhun Karimov wrote:
>>> Hi,
>>>
>>> Thanks for comments. I extended PR and KIP to include rich functions. I
>>> will still have to evaluate the cost of deep copying of keys.
>>>
>>> Cheers,
>>> Jeyhun
>>>
>>> On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak 
>>>  
>>> wrote:
>>>
 Hey Matthias,

 My opinion would be that documenting the immutability of the key is the
 best approach available.  Better than requiring the key to be 
 serializable
 (as with Jeyhun's last pass at the PR), no performance risk.

 It'd be different if Java had immutable type constraints of some kind. 
 :-)

 Mathieu


 On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax 
  
 wrote:

> Agreed about RichFunction. If we follow this path, it should cover
> all(?) DSL interfaces.
>
> About guarding the key -- I am still not sure what to do about it...
> Maybe it might be enough to document it (and name the key parameter 
> like
> `readOnlyKey` to make is very clear). Ultimately, I would prefer to
> guard against any modification, but I have no good idea how to do 
> this.
> Not sure what others think about the risk of corrupted partitioning
> (what would be a user error and we could say, well, bad luck, you got 
> a
> bug in your code, that's not our fault), vs deep copy with a potential
> performance hit (that we can't quantity atm without any performance
 test).
> We do have a performance system test. Maybe it's worth for you to 
> apply
> the deep copy strategy and run the test. It's very basic performance
> test only, but might give some insight. If you want to do this, look
> into folder "tests" for general test setup, and into
> "tests/kafaktests/benchmarks/streams" to find find the perf test.
>
>
> -Matthias
>
> On 5/5/17 8:55 AM, Jeyhun Karimov wrote:
>> Hi Matthias,
>>
>> I think extending KIP to include RichFunctions totally  makes sense.
 So,
>>  we don't want to guard the keys because it is costly.
>> If we introduce RichFunctions I think it should not be limited only
 the 3
>> interfaces proposed in KIP but to wide range of interfaces.
>> Please correct me if I am wrong.
>>
>> Cheers,
>> Jeyhun
>>
>> On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax 
>> 
>> wrote:
>>
>>> One follow up. There was this email on the user list:
>>>
>>>
>>> http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=
> Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+
>>> It might make sense so include Initializer, Adder, and Substractor
>>> 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Michal Borowiecki]

Hi Jeyhun,

Thanks for your quick reply.

Indeed, I understand the existing ValueMapper/Joiner etc. have to remain 
as-is for backwards compatibility.


I was just expressing my surprise that their proposed richer equivalents 
weren't functional interfaces too.


Thanks,

Michał


On 07/05/17 12:32, Jeyhun Karimov wrote:

Hi Michal,

Thanks for your comments. We proposed the similar solution to yours in 
KIP (please look at rejected alternatives). However, after the 
discussion in mailing list I extended it to rich functions. Maybe we 
should keep them both: simple and rich versions.


Cheers,
Jeyhun

On Sun, May 7, 2017 at 11:46 AM Michal Borowiecki 
> 
wrote:


Do I understanding correctly, that with the proposed pattern one
could not pass a lambda expression and access the context from
within it?

TBH, I was hoping that for simple things this would be possible:

myStream.map( (key, value, ctx) -> new KeyValue<>(ctx.partition(),
value) )

or (more to the original point of this KIP):

myStream.mapValues( (key, value, ctx) -> new MyValueWrapper(value,
ctx.partition(), ctx.offset()) )

but it looks like that would require subclassing RichFunction?
That's a bit of an inconvenience IMO.

Cheers,

Michal


On 07/05/17 01:29, Jeyhun Karimov wrote:

Hi,

Thanks for comments. I extended PR and KIP to include rich functions. I
will still have to evaluate the cost of deep copying of keys.

Cheers,
Jeyhun

On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak 

wrote:


Hey Matthias,

My opinion would be that documenting the immutability of the key is the
best approach available.  Better than requiring the key to be serializable
(as with Jeyhun's last pass at the PR), no performance risk.

It'd be different if Java had immutable type constraints of some kind. :-)

Mathieu


On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax 

wrote:


Agreed about RichFunction. If we follow this path, it should cover
all(?) DSL interfaces.

About guarding the key -- I am still not sure what to do about it...
Maybe it might be enough to document it (and name the key parameter like
`readOnlyKey` to make is very clear). Ultimately, I would prefer to
guard against any modification, but I have no good idea how to do this.
Not sure what others think about the risk of corrupted partitioning
(what would be a user error and we could say, well, bad luck, you got a
bug in your code, that's not our fault), vs deep copy with a potential
performance hit (that we can't quantity atm without any performance

test).

We do have a performance system test. Maybe it's worth for you to apply
the deep copy strategy and run the test. It's very basic performance
test only, but might give some insight. If you want to do this, look
into folder "tests" for general test setup, and into
"tests/kafaktests/benchmarks/streams" to find find the perf test.


-Matthias

On 5/5/17 8:55 AM, Jeyhun Karimov wrote:

Hi Matthias,

I think extending KIP to include RichFunctions totally  makes sense.

So,

  we don't want to guard the keys because it is costly.
If we introduce RichFunctions I think it should not be limited only

the 3

interfaces proposed in KIP but to wide range of interfaces.
Please correct me if I am wrong.

Cheers,
Jeyhun

On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax 
wrote:


One follow up. There was this email on the user list:


http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=

Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+

It might make sense so include Initializer, Adder, and Substractor
inferface, too.

And we should double check if there are other interface we might miss

atm.

-Matthias


On 5/4/17 1:31 PM, Matthias J. Sax wrote:

Thanks for updating the KIP.

Deep copying the key will work for sure, but I am actually a little

bit

worried about performance impact... We might want to do some test to
quantify this impact.


Btw: this remind me about the idea of `RichFunction` interface that
would allow users to access record metadata (like timestamp, offset,
partition etc) within DSL. This would be a similar concept. Thus, I

am

wondering, if it would make sense to enlarge the scope of this KIP by
that? WDYT?



-Matthias


On 5/3/17 2:08 AM, Jeyhun Karimov wrote:

Hi Mathieu,

Thanks for feedback. I followed similar approach and updated PR and

KIP

accordingly. I tried to guard the key in Processors sending a copy

of

an

actual key.

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi Michal,

Thanks for your comments. We proposed the similar solution to yours in KIP
(please look at rejected alternatives). However, after the discussion in
mailing list I extended it to rich functions. Maybe we should keep them
both: simple and rich versions.

Cheers,
Jeyhun

On Sun, May 7, 2017 at 11:46 AM Michal Borowiecki <
michal.borowie...@openbet.com> wrote:

> Do I understanding correctly, that with the proposed pattern one could not
> pass a lambda expression and access the context from within it?
>
> TBH, I was hoping that for simple things this would be possible:
>
> myStream.map( (key, value, ctx) -> new KeyValue<>(ctx.partition(), value) )
>
> or (more to the original point of this KIP):
>
> myStream.mapValues( (key, value, ctx) -> new MyValueWrapper(value,
> ctx.partition(), ctx.offset()) )
>
> but it looks like that would require subclassing RichFunction? That's a
> bit of an inconvenience IMO.
>
> Cheers,
>
> Michal
>
> On 07/05/17 01:29, Jeyhun Karimov wrote:
>
> Hi,
>
> Thanks for comments. I extended PR and KIP to include rich functions. I
> will still have to evaluate the cost of deep copying of keys.
>
> Cheers,
> Jeyhun
>
> On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak  
> 
> wrote:
>
>
> Hey Matthias,
>
> My opinion would be that documenting the immutability of the key is the
> best approach available.  Better than requiring the key to be serializable
> (as with Jeyhun's last pass at the PR), no performance risk.
>
> It'd be different if Java had immutable type constraints of some kind. :-)
>
> Mathieu
>
>
> On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax  
> 
> wrote:
>
>
> Agreed about RichFunction. If we follow this path, it should cover
> all(?) DSL interfaces.
>
> About guarding the key -- I am still not sure what to do about it...
> Maybe it might be enough to document it (and name the key parameter like
> `readOnlyKey` to make is very clear). Ultimately, I would prefer to
> guard against any modification, but I have no good idea how to do this.
> Not sure what others think about the risk of corrupted partitioning
> (what would be a user error and we could say, well, bad luck, you got a
> bug in your code, that's not our fault), vs deep copy with a potential
> performance hit (that we can't quantity atm without any performance
>
> test).
>
>
> We do have a performance system test. Maybe it's worth for you to apply
> the deep copy strategy and run the test. It's very basic performance
> test only, but might give some insight. If you want to do this, look
> into folder "tests" for general test setup, and into
> "tests/kafaktests/benchmarks/streams" to find find the perf test.
>
>
> -Matthias
>
> On 5/5/17 8:55 AM, Jeyhun Karimov wrote:
>
> Hi Matthias,
>
> I think extending KIP to include RichFunctions totally  makes sense.
>
> So,
>
>  we don't want to guard the keys because it is costly.
> If we introduce RichFunctions I think it should not be limited only
>
> the 3
>
> interfaces proposed in KIP but to wide range of interfaces.
> Please correct me if I am wrong.
>
> Cheers,
> Jeyhun
>
> On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax 
>  wrote:
>
>
> One follow up. There was this email on the user list:
>
> http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=
>
> Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+
>
>
> It might make sense so include Initializer, Adder, and Substractor
> inferface, too.
>
> And we should double check if there are other interface we might miss
>
> atm.
>
>
>
> -Matthias
>
>
> On 5/4/17 1:31 PM, Matthias J. Sax wrote:
>
> Thanks for updating the KIP.
>
> Deep copying the key will work for sure, but I am actually a little
>
> bit
>
> worried about performance impact... We might want to do some test to
> quantify this impact.
>
>
> Btw: this remind me about the idea of `RichFunction` interface that
> would allow users to access record metadata (like timestamp, offset,
> partition etc) within DSL. This would be a similar concept. Thus, I
>
> am
>
> wondering, if it would make sense to enlarge the scope of this KIP by
> that? WDYT?
>
>
>
> -Matthias
>
>
> On 5/3/17 2:08 AM, Jeyhun Karimov wrote:
>
> Hi Mathieu,
>
> Thanks for feedback. I followed similar approach and updated PR and
>
> KIP
>
> accordingly. I tried to guard the key in Processors sending a copy
>
> of
>
> an
>
> actual key.
> Because I am doing deep copy of an object, I think memory can be
>
> bottleneck
>
> in some use-cases.
>
> Cheers,
> Jeyhun
>
> On Tue, May 2, 2017 at 5:10 PM Mathieu Fenniak <
>
> mathieu.fenn...@replicon.com>
>
> wrote:
>
>
> Hi Jeyhun,
>
> This approach would change ValueMapper (...etc) to be classes,
>
> rather
>
> than
>
> interfaces, which is also a backwards incompatible change.  An
>
> alternative
>
> approach that would be backwards compatible would be to define new
> interfaces, and provide overrides 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Michal Borowiecki]

Do I understanding correctly, that with the proposed pattern one could 
not pass a lambda expression and access the context from within it?


TBH, I was hoping that for simple things this would be possible:

myStream.map( (key, value, ctx) -> new KeyValue<>(ctx.partition(), value) )

or (more to the original point of this KIP):

myStream.mapValues( (key, value, ctx) -> new MyValueWrapper(value, 
ctx.partition(), ctx.offset()) )


but it looks like that would require subclassing RichFunction? That's a 
bit of an inconvenience IMO.


Cheers,

Michal


On 07/05/17 01:29, Jeyhun Karimov wrote:

Hi,

Thanks for comments. I extended PR and KIP to include rich functions. I
will still have to evaluate the cost of deep copying of keys.

Cheers,
Jeyhun

On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak 
wrote:


Hey Matthias,

My opinion would be that documenting the immutability of the key is the
best approach available.  Better than requiring the key to be serializable
(as with Jeyhun's last pass at the PR), no performance risk.

It'd be different if Java had immutable type constraints of some kind. :-)

Mathieu


On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax 
wrote:


Agreed about RichFunction. If we follow this path, it should cover
all(?) DSL interfaces.

About guarding the key -- I am still not sure what to do about it...
Maybe it might be enough to document it (and name the key parameter like
`readOnlyKey` to make is very clear). Ultimately, I would prefer to
guard against any modification, but I have no good idea how to do this.
Not sure what others think about the risk of corrupted partitioning
(what would be a user error and we could say, well, bad luck, you got a
bug in your code, that's not our fault), vs deep copy with a potential
performance hit (that we can't quantity atm without any performance

test).

We do have a performance system test. Maybe it's worth for you to apply
the deep copy strategy and run the test. It's very basic performance
test only, but might give some insight. If you want to do this, look
into folder "tests" for general test setup, and into
"tests/kafaktests/benchmarks/streams" to find find the perf test.


-Matthias

On 5/5/17 8:55 AM, Jeyhun Karimov wrote:

Hi Matthias,

I think extending KIP to include RichFunctions totally  makes sense.

So,

  we don't want to guard the keys because it is costly.
If we introduce RichFunctions I think it should not be limited only

the 3

interfaces proposed in KIP but to wide range of interfaces.
Please correct me if I am wrong.

Cheers,
Jeyhun

On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax 

wrote:


Hi Jeyhun,

This approach would change ValueMapper (...etc) to be classes,

rather

than

interfaces, which is also a backwards incompatible change.  An

alternative

approach that would be backwards compatible would be to define new
interfaces, and provide overrides where those interfaces are used.

Unfortunately, making the key parameter as "final" doesn't change

much

about guarding against key change.  It only prevents the parameter

variable

from being reassigned.  If the key type is a mutable object (eg.

byte[]),

it can still be mutated. (eg. key[0] = 0).  But I'm not really sure

there's

much that can be done about that.

Mathieu


On Mon, May 1, 2017 at 5:39 PM, Jeyhun Karimov <

je.kari...@gmail.com

wrote:


Thanks for comments.

The concerns makes sense. Although we can guard for immutable keys

in

current implementation (with few changes), I didn't consider

backward

compatibility.

In this case 2 solutions come to my mind. In both cases, user

accesses

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi,

Thanks for comments. I extended PR and KIP to include rich functions. I
will still have to evaluate the cost of deep copying of keys.

Cheers,
Jeyhun

On Fri, May 5, 2017 at 8:02 PM Mathieu Fenniak 
wrote:

> Hey Matthias,
>
> My opinion would be that documenting the immutability of the key is the
> best approach available.  Better than requiring the key to be serializable
> (as with Jeyhun's last pass at the PR), no performance risk.
>
> It'd be different if Java had immutable type constraints of some kind. :-)
>
> Mathieu
>
>
> On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax 
> wrote:
>
> > Agreed about RichFunction. If we follow this path, it should cover
> > all(?) DSL interfaces.
> >
> > About guarding the key -- I am still not sure what to do about it...
> > Maybe it might be enough to document it (and name the key parameter like
> > `readOnlyKey` to make is very clear). Ultimately, I would prefer to
> > guard against any modification, but I have no good idea how to do this.
> > Not sure what others think about the risk of corrupted partitioning
> > (what would be a user error and we could say, well, bad luck, you got a
> > bug in your code, that's not our fault), vs deep copy with a potential
> > performance hit (that we can't quantity atm without any performance
> test).
> >
> > We do have a performance system test. Maybe it's worth for you to apply
> > the deep copy strategy and run the test. It's very basic performance
> > test only, but might give some insight. If you want to do this, look
> > into folder "tests" for general test setup, and into
> > "tests/kafaktests/benchmarks/streams" to find find the perf test.
> >
> >
> > -Matthias
> >
> > On 5/5/17 8:55 AM, Jeyhun Karimov wrote:
> > > Hi Matthias,
> > >
> > > I think extending KIP to include RichFunctions totally  makes sense.
> So,
> > >  we don't want to guard the keys because it is costly.
> > > If we introduce RichFunctions I think it should not be limited only
> the 3
> > > interfaces proposed in KIP but to wide range of interfaces.
> > > Please correct me if I am wrong.
> > >
> > > Cheers,
> > > Jeyhun
> > >
> > > On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax  >
> > > wrote:
> > >
> > >> One follow up. There was this email on the user list:
> > >>
> > >>
> > >> http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=
> > Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+
> > >>
> > >> It might make sense so include Initializer, Adder, and Substractor
> > >> inferface, too.
> > >>
> > >> And we should double check if there are other interface we might miss
> > atm.
> > >>
> > >>
> > >> -Matthias
> > >>
> > >>
> > >> On 5/4/17 1:31 PM, Matthias J. Sax wrote:
> > >>> Thanks for updating the KIP.
> > >>>
> > >>> Deep copying the key will work for sure, but I am actually a little
> bit
> > >>> worried about performance impact... We might want to do some test to
> > >>> quantify this impact.
> > >>>
> > >>>
> > >>> Btw: this remind me about the idea of `RichFunction` interface that
> > >>> would allow users to access record metadata (like timestamp, offset,
> > >>> partition etc) within DSL. This would be a similar concept. Thus, I
> am
> > >>> wondering, if it would make sense to enlarge the scope of this KIP by
> > >>> that? WDYT?
> > >>>
> > >>>
> > >>>
> > >>> -Matthias
> > >>>
> > >>>
> > >>> On 5/3/17 2:08 AM, Jeyhun Karimov wrote:
> >  Hi Mathieu,
> > 
> >  Thanks for feedback. I followed similar approach and updated PR and
> > KIP
> >  accordingly. I tried to guard the key in Processors sending a copy
> of
> > an
> >  actual key.
> >  Because I am doing deep copy of an object, I think memory can be
> > >> bottleneck
> >  in some use-cases.
> > 
> >  Cheers,
> >  Jeyhun
> > 
> >  On Tue, May 2, 2017 at 5:10 PM Mathieu Fenniak <
> > >> mathieu.fenn...@replicon.com>
> >  wrote:
> > 
> > > Hi Jeyhun,
> > >
> > > This approach would change ValueMapper (...etc) to be classes,
> rather
> > >> than
> > > interfaces, which is also a backwards incompatible change.  An
> > >> alternative
> > > approach that would be backwards compatible would be to define new
> > > interfaces, and provide overrides where those interfaces are used.
> > >
> > > Unfortunately, making the key parameter as "final" doesn't change
> > much
> > > about guarding against key change.  It only prevents the parameter
> > >> variable
> > > from being reassigned.  If the key type is a mutable object (eg.
> > >> byte[]),
> > > it can still be mutated. (eg. key[0] = 0).  But I'm not really sure
> > >> there's
> > > much that can be done about that.
> > >
> > > Mathieu
> > >
> > >
> > > On Mon, May 1, 2017 at 5:39 PM, Jeyhun Karimov <
> je.kari...@gmail.com
> > >
> > > wrote:
> > >
> > >> Thanks for comments.
> > >>
> > >> The concerns 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Mathieu Fenniak]

Hey Matthias,

My opinion would be that documenting the immutability of the key is the
best approach available.  Better than requiring the key to be serializable
(as with Jeyhun's last pass at the PR), no performance risk.

It'd be different if Java had immutable type constraints of some kind. :-)

Mathieu


On Fri, May 5, 2017 at 11:31 AM, Matthias J. Sax 
wrote:

> Agreed about RichFunction. If we follow this path, it should cover
> all(?) DSL interfaces.
>
> About guarding the key -- I am still not sure what to do about it...
> Maybe it might be enough to document it (and name the key parameter like
> `readOnlyKey` to make is very clear). Ultimately, I would prefer to
> guard against any modification, but I have no good idea how to do this.
> Not sure what others think about the risk of corrupted partitioning
> (what would be a user error and we could say, well, bad luck, you got a
> bug in your code, that's not our fault), vs deep copy with a potential
> performance hit (that we can't quantity atm without any performance test).
>
> We do have a performance system test. Maybe it's worth for you to apply
> the deep copy strategy and run the test. It's very basic performance
> test only, but might give some insight. If you want to do this, look
> into folder "tests" for general test setup, and into
> "tests/kafaktests/benchmarks/streams" to find find the perf test.
>
>
> -Matthias
>
> On 5/5/17 8:55 AM, Jeyhun Karimov wrote:
> > Hi Matthias,
> >
> > I think extending KIP to include RichFunctions totally  makes sense. So,
> >  we don't want to guard the keys because it is costly.
> > If we introduce RichFunctions I think it should not be limited only the 3
> > interfaces proposed in KIP but to wide range of interfaces.
> > Please correct me if I am wrong.
> >
> > Cheers,
> > Jeyhun
> >
> > On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax 
> > wrote:
> >
> >> One follow up. There was this email on the user list:
> >>
> >>
> >> http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=
> Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+
> >>
> >> It might make sense so include Initializer, Adder, and Substractor
> >> inferface, too.
> >>
> >> And we should double check if there are other interface we might miss
> atm.
> >>
> >>
> >> -Matthias
> >>
> >>
> >> On 5/4/17 1:31 PM, Matthias J. Sax wrote:
> >>> Thanks for updating the KIP.
> >>>
> >>> Deep copying the key will work for sure, but I am actually a little bit
> >>> worried about performance impact... We might want to do some test to
> >>> quantify this impact.
> >>>
> >>>
> >>> Btw: this remind me about the idea of `RichFunction` interface that
> >>> would allow users to access record metadata (like timestamp, offset,
> >>> partition etc) within DSL. This would be a similar concept. Thus, I am
> >>> wondering, if it would make sense to enlarge the scope of this KIP by
> >>> that? WDYT?
> >>>
> >>>
> >>>
> >>> -Matthias
> >>>
> >>>
> >>> On 5/3/17 2:08 AM, Jeyhun Karimov wrote:
>  Hi Mathieu,
> 
>  Thanks for feedback. I followed similar approach and updated PR and
> KIP
>  accordingly. I tried to guard the key in Processors sending a copy of
> an
>  actual key.
>  Because I am doing deep copy of an object, I think memory can be
> >> bottleneck
>  in some use-cases.
> 
>  Cheers,
>  Jeyhun
> 
>  On Tue, May 2, 2017 at 5:10 PM Mathieu Fenniak <
> >> mathieu.fenn...@replicon.com>
>  wrote:
> 
> > Hi Jeyhun,
> >
> > This approach would change ValueMapper (...etc) to be classes, rather
> >> than
> > interfaces, which is also a backwards incompatible change.  An
> >> alternative
> > approach that would be backwards compatible would be to define new
> > interfaces, and provide overrides where those interfaces are used.
> >
> > Unfortunately, making the key parameter as "final" doesn't change
> much
> > about guarding against key change.  It only prevents the parameter
> >> variable
> > from being reassigned.  If the key type is a mutable object (eg.
> >> byte[]),
> > it can still be mutated. (eg. key[0] = 0).  But I'm not really sure
> >> there's
> > much that can be done about that.
> >
> > Mathieu
> >
> >
> > On Mon, May 1, 2017 at 5:39 PM, Jeyhun Karimov  >
> > wrote:
> >
> >> Thanks for comments.
> >>
> >> The concerns makes sense. Although we can guard for immutable keys
> in
> >> current implementation (with few changes), I didn't consider
> backward
> >> compatibility.
> >>
> >> In this case 2 solutions come to my mind. In both cases, user
> accesses
> > the
> >> key in Object type, as passing extra type parameter will break
> >> backwards-compatibility.  So user has to cast to actual key type.
> >>
> >> 1. Firstly, We can overload apply method with 2 argument (key and
> >> value)
> >> and 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Agreed about RichFunction. If we follow this path, it should cover
all(?) DSL interfaces.

About guarding the key -- I am still not sure what to do about it...
Maybe it might be enough to document it (and name the key parameter like
`readOnlyKey` to make is very clear). Ultimately, I would prefer to
guard against any modification, but I have no good idea how to do this.
Not sure what others think about the risk of corrupted partitioning
(what would be a user error and we could say, well, bad luck, you got a
bug in your code, that's not our fault), vs deep copy with a potential
performance hit (that we can't quantity atm without any performance test).

We do have a performance system test. Maybe it's worth for you to apply
the deep copy strategy and run the test. It's very basic performance
test only, but might give some insight. If you want to do this, look
into folder "tests" for general test setup, and into
"tests/kafaktests/benchmarks/streams" to find find the perf test.


-Matthias

On 5/5/17 8:55 AM, Jeyhun Karimov wrote:
> Hi Matthias,
> 
> I think extending KIP to include RichFunctions totally  makes sense. So,
>  we don't want to guard the keys because it is costly.
> If we introduce RichFunctions I think it should not be limited only the 3
> interfaces proposed in KIP but to wide range of interfaces.
> Please correct me if I am wrong.
> 
> Cheers,
> Jeyhun
> 
> On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax 
> wrote:
> 
>> One follow up. There was this email on the user list:
>>
>>
>> http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+
>>
>> It might make sense so include Initializer, Adder, and Substractor
>> inferface, too.
>>
>> And we should double check if there are other interface we might miss atm.
>>
>>
>> -Matthias
>>
>>
>> On 5/4/17 1:31 PM, Matthias J. Sax wrote:
>>> Thanks for updating the KIP.
>>>
>>> Deep copying the key will work for sure, but I am actually a little bit
>>> worried about performance impact... We might want to do some test to
>>> quantify this impact.
>>>
>>>
>>> Btw: this remind me about the idea of `RichFunction` interface that
>>> would allow users to access record metadata (like timestamp, offset,
>>> partition etc) within DSL. This would be a similar concept. Thus, I am
>>> wondering, if it would make sense to enlarge the scope of this KIP by
>>> that? WDYT?
>>>
>>>
>>>
>>> -Matthias
>>>
>>>
>>> On 5/3/17 2:08 AM, Jeyhun Karimov wrote:
 Hi Mathieu,

 Thanks for feedback. I followed similar approach and updated PR and KIP
 accordingly. I tried to guard the key in Processors sending a copy of an
 actual key.
 Because I am doing deep copy of an object, I think memory can be
>> bottleneck
 in some use-cases.

 Cheers,
 Jeyhun

 On Tue, May 2, 2017 at 5:10 PM Mathieu Fenniak <
>> mathieu.fenn...@replicon.com>
 wrote:

> Hi Jeyhun,
>
> This approach would change ValueMapper (...etc) to be classes, rather
>> than
> interfaces, which is also a backwards incompatible change.  An
>> alternative
> approach that would be backwards compatible would be to define new
> interfaces, and provide overrides where those interfaces are used.
>
> Unfortunately, making the key parameter as "final" doesn't change much
> about guarding against key change.  It only prevents the parameter
>> variable
> from being reassigned.  If the key type is a mutable object (eg.
>> byte[]),
> it can still be mutated. (eg. key[0] = 0).  But I'm not really sure
>> there's
> much that can be done about that.
>
> Mathieu
>
>
> On Mon, May 1, 2017 at 5:39 PM, Jeyhun Karimov 
> wrote:
>
>> Thanks for comments.
>>
>> The concerns makes sense. Although we can guard for immutable keys in
>> current implementation (with few changes), I didn't consider backward
>> compatibility.
>>
>> In this case 2 solutions come to my mind. In both cases, user accesses
> the
>> key in Object type, as passing extra type parameter will break
>> backwards-compatibility.  So user has to cast to actual key type.
>>
>> 1. Firstly, We can overload apply method with 2 argument (key and
>> value)
>> and force key to be *final*. By doing this,  I think we can address
>> both
>> backward-compatibility and guarding against key change.
>>
>> 2. Secondly, we can create class KeyAccess like:
>>
>> public class KeyAccess {
>> Object key;
>> public void beforeApply(final Object key) {
>> this.key = key;
>> }
>> public Object getKey() {
>> return key;
>> }
>> }
>>
>> We can extend *ValueMapper, ValueJoiner* and *ValueTransformer* from
>> *KeyAccess*. Inside processor (for example *KTableMapValuesProcessor*)
>> before calling *mapper.apply(value)* we 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi Matthias,

I think extending KIP to include RichFunctions totally  makes sense. So,
 we don't want to guard the keys because it is costly.
If we introduce RichFunctions I think it should not be limited only the 3
interfaces proposed in KIP but to wide range of interfaces.
Please correct me if I am wrong.

Cheers,
Jeyhun

On Fri, May 5, 2017 at 12:04 AM Matthias J. Sax 
wrote:

> One follow up. There was this email on the user list:
>
>
> http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+
>
> It might make sense so include Initializer, Adder, and Substractor
> inferface, too.
>
> And we should double check if there are other interface we might miss atm.
>
>
> -Matthias
>
>
> On 5/4/17 1:31 PM, Matthias J. Sax wrote:
> > Thanks for updating the KIP.
> >
> > Deep copying the key will work for sure, but I am actually a little bit
> > worried about performance impact... We might want to do some test to
> > quantify this impact.
> >
> >
> > Btw: this remind me about the idea of `RichFunction` interface that
> > would allow users to access record metadata (like timestamp, offset,
> > partition etc) within DSL. This would be a similar concept. Thus, I am
> > wondering, if it would make sense to enlarge the scope of this KIP by
> > that? WDYT?
> >
> >
> >
> > -Matthias
> >
> >
> > On 5/3/17 2:08 AM, Jeyhun Karimov wrote:
> >> Hi Mathieu,
> >>
> >> Thanks for feedback. I followed similar approach and updated PR and KIP
> >> accordingly. I tried to guard the key in Processors sending a copy of an
> >> actual key.
> >> Because I am doing deep copy of an object, I think memory can be
> bottleneck
> >> in some use-cases.
> >>
> >> Cheers,
> >> Jeyhun
> >>
> >> On Tue, May 2, 2017 at 5:10 PM Mathieu Fenniak <
> mathieu.fenn...@replicon.com>
> >> wrote:
> >>
> >>> Hi Jeyhun,
> >>>
> >>> This approach would change ValueMapper (...etc) to be classes, rather
> than
> >>> interfaces, which is also a backwards incompatible change.  An
> alternative
> >>> approach that would be backwards compatible would be to define new
> >>> interfaces, and provide overrides where those interfaces are used.
> >>>
> >>> Unfortunately, making the key parameter as "final" doesn't change much
> >>> about guarding against key change.  It only prevents the parameter
> variable
> >>> from being reassigned.  If the key type is a mutable object (eg.
> byte[]),
> >>> it can still be mutated. (eg. key[0] = 0).  But I'm not really sure
> there's
> >>> much that can be done about that.
> >>>
> >>> Mathieu
> >>>
> >>>
> >>> On Mon, May 1, 2017 at 5:39 PM, Jeyhun Karimov 
> >>> wrote:
> >>>
>  Thanks for comments.
> 
>  The concerns makes sense. Although we can guard for immutable keys in
>  current implementation (with few changes), I didn't consider backward
>  compatibility.
> 
>  In this case 2 solutions come to my mind. In both cases, user accesses
> >>> the
>  key in Object type, as passing extra type parameter will break
>  backwards-compatibility.  So user has to cast to actual key type.
> 
>  1. Firstly, We can overload apply method with 2 argument (key and
> value)
>  and force key to be *final*. By doing this,  I think we can address
> both
>  backward-compatibility and guarding against key change.
> 
>  2. Secondly, we can create class KeyAccess like:
> 
>  public class KeyAccess {
>  Object key;
>  public void beforeApply(final Object key) {
>  this.key = key;
>  }
>  public Object getKey() {
>  return key;
>  }
>  }
> 
>  We can extend *ValueMapper, ValueJoiner* and *ValueTransformer* from
>  *KeyAccess*. Inside processor (for example *KTableMapValuesProcessor*)
>  before calling *mapper.apply(value)* we can set the *key* by
>  *mapper.beforeApply(key)*. As a result, user can use *getKey()* to
> access
>  the key inside *apply(value)* method.
> 
> 
>  Cheers,
>  Jeyhun
> 
> 
> 
> 
>  On Mon, May 1, 2017 at 7:24 PM Matthias J. Sax  >
>  wrote:
> 
> > Jeyhun,
> >
> > thanks a lot for the KIP!
> >
> > I think there are two issues we need to address:
> >
> > (1) The KIP does not consider backward compatibility. Users did
> >>> complain
> > about this in past releases already, and as the user base grows, we
> > should not break backward compatibility in future releases anymore.
> > Thus, we should think of a better way to allow key access.
> >
> > Mathieu's comment goes into the same direction
> >
> >>> On the other hand, the number of compile failures that would need
> to
>  be
> >>> fixed from this change is unfortunate. :-)
> >
> > (2) Another concern is, that there is no guard to prevent user code
> to
> > modify the key. This 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

One follow up. There was this email on the user list:

http://search-hadoop.com/m/Kafka/uyzND17KhCaBzPSZ1?subj=Shouldn+t+the+initializer+of+a+stream+aggregate+accept+the+key+

It might make sense so include Initializer, Adder, and Substractor
inferface, too.

And we should double check if there are other interface we might miss atm.


-Matthias


On 5/4/17 1:31 PM, Matthias J. Sax wrote:
> Thanks for updating the KIP.
> 
> Deep copying the key will work for sure, but I am actually a little bit
> worried about performance impact... We might want to do some test to
> quantify this impact.
> 
> 
> Btw: this remind me about the idea of `RichFunction` interface that
> would allow users to access record metadata (like timestamp, offset,
> partition etc) within DSL. This would be a similar concept. Thus, I am
> wondering, if it would make sense to enlarge the scope of this KIP by
> that? WDYT?
> 
> 
> 
> -Matthias
> 
> 
> On 5/3/17 2:08 AM, Jeyhun Karimov wrote:
>> Hi Mathieu,
>>
>> Thanks for feedback. I followed similar approach and updated PR and KIP
>> accordingly. I tried to guard the key in Processors sending a copy of an
>> actual key.
>> Because I am doing deep copy of an object, I think memory can be bottleneck
>> in some use-cases.
>>
>> Cheers,
>> Jeyhun
>>
>> On Tue, May 2, 2017 at 5:10 PM Mathieu Fenniak 
>> wrote:
>>
>>> Hi Jeyhun,
>>>
>>> This approach would change ValueMapper (...etc) to be classes, rather than
>>> interfaces, which is also a backwards incompatible change.  An alternative
>>> approach that would be backwards compatible would be to define new
>>> interfaces, and provide overrides where those interfaces are used.
>>>
>>> Unfortunately, making the key parameter as "final" doesn't change much
>>> about guarding against key change.  It only prevents the parameter variable
>>> from being reassigned.  If the key type is a mutable object (eg. byte[]),
>>> it can still be mutated. (eg. key[0] = 0).  But I'm not really sure there's
>>> much that can be done about that.
>>>
>>> Mathieu
>>>
>>>
>>> On Mon, May 1, 2017 at 5:39 PM, Jeyhun Karimov 
>>> wrote:
>>>
 Thanks for comments.

 The concerns makes sense. Although we can guard for immutable keys in
 current implementation (with few changes), I didn't consider backward
 compatibility.

 In this case 2 solutions come to my mind. In both cases, user accesses
>>> the
 key in Object type, as passing extra type parameter will break
 backwards-compatibility.  So user has to cast to actual key type.

 1. Firstly, We can overload apply method with 2 argument (key and value)
 and force key to be *final*. By doing this,  I think we can address both
 backward-compatibility and guarding against key change.

 2. Secondly, we can create class KeyAccess like:

 public class KeyAccess {
 Object key;
 public void beforeApply(final Object key) {
 this.key = key;
 }
 public Object getKey() {
 return key;
 }
 }

 We can extend *ValueMapper, ValueJoiner* and *ValueTransformer* from
 *KeyAccess*. Inside processor (for example *KTableMapValuesProcessor*)
 before calling *mapper.apply(value)* we can set the *key* by
 *mapper.beforeApply(key)*. As a result, user can use *getKey()* to access
 the key inside *apply(value)* method.


 Cheers,
 Jeyhun




 On Mon, May 1, 2017 at 7:24 PM Matthias J. Sax 
 wrote:

> Jeyhun,
>
> thanks a lot for the KIP!
>
> I think there are two issues we need to address:
>
> (1) The KIP does not consider backward compatibility. Users did
>>> complain
> about this in past releases already, and as the user base grows, we
> should not break backward compatibility in future releases anymore.
> Thus, we should think of a better way to allow key access.
>
> Mathieu's comment goes into the same direction
>
>>> On the other hand, the number of compile failures that would need to
 be
>>> fixed from this change is unfortunate. :-)
>
> (2) Another concern is, that there is no guard to prevent user code to
> modify the key. This might corrupt partitioning if users do alter the
> key (accidentally -- or users are just not aware that they are not
> allowed to modify the provided key object) and thus break the
> application. (This was the original motivation to not provide the key
>>> in
> the first place -- it's guards against modification.)
>
>
> -Matthias
>
>
>
> On 5/1/17 6:31 AM, Mathieu Fenniak wrote:
>> Hi Jeyhun,
>>
>> I just want to add my voice that, I too, have wished for access to
>>> the
>> record key during a mapValues or similar operation.
>>
>> On the other hand, the number of compile failures that would need to
>>> be

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Thanks for updating the KIP.

Deep copying the key will work for sure, but I am actually a little bit
worried about performance impact... We might want to do some test to
quantify this impact.


Btw: this remind me about the idea of `RichFunction` interface that
would allow users to access record metadata (like timestamp, offset,
partition etc) within DSL. This would be a similar concept. Thus, I am
wondering, if it would make sense to enlarge the scope of this KIP by
that? WDYT?



-Matthias


On 5/3/17 2:08 AM, Jeyhun Karimov wrote:
> Hi Mathieu,
> 
> Thanks for feedback. I followed similar approach and updated PR and KIP
> accordingly. I tried to guard the key in Processors sending a copy of an
> actual key.
> Because I am doing deep copy of an object, I think memory can be bottleneck
> in some use-cases.
> 
> Cheers,
> Jeyhun
> 
> On Tue, May 2, 2017 at 5:10 PM Mathieu Fenniak 
> wrote:
> 
>> Hi Jeyhun,
>>
>> This approach would change ValueMapper (...etc) to be classes, rather than
>> interfaces, which is also a backwards incompatible change.  An alternative
>> approach that would be backwards compatible would be to define new
>> interfaces, and provide overrides where those interfaces are used.
>>
>> Unfortunately, making the key parameter as "final" doesn't change much
>> about guarding against key change.  It only prevents the parameter variable
>> from being reassigned.  If the key type is a mutable object (eg. byte[]),
>> it can still be mutated. (eg. key[0] = 0).  But I'm not really sure there's
>> much that can be done about that.
>>
>> Mathieu
>>
>>
>> On Mon, May 1, 2017 at 5:39 PM, Jeyhun Karimov 
>> wrote:
>>
>>> Thanks for comments.
>>>
>>> The concerns makes sense. Although we can guard for immutable keys in
>>> current implementation (with few changes), I didn't consider backward
>>> compatibility.
>>>
>>> In this case 2 solutions come to my mind. In both cases, user accesses
>> the
>>> key in Object type, as passing extra type parameter will break
>>> backwards-compatibility.  So user has to cast to actual key type.
>>>
>>> 1. Firstly, We can overload apply method with 2 argument (key and value)
>>> and force key to be *final*. By doing this,  I think we can address both
>>> backward-compatibility and guarding against key change.
>>>
>>> 2. Secondly, we can create class KeyAccess like:
>>>
>>> public class KeyAccess {
>>> Object key;
>>> public void beforeApply(final Object key) {
>>> this.key = key;
>>> }
>>> public Object getKey() {
>>> return key;
>>> }
>>> }
>>>
>>> We can extend *ValueMapper, ValueJoiner* and *ValueTransformer* from
>>> *KeyAccess*. Inside processor (for example *KTableMapValuesProcessor*)
>>> before calling *mapper.apply(value)* we can set the *key* by
>>> *mapper.beforeApply(key)*. As a result, user can use *getKey()* to access
>>> the key inside *apply(value)* method.
>>>
>>>
>>> Cheers,
>>> Jeyhun
>>>
>>>
>>>
>>>
>>> On Mon, May 1, 2017 at 7:24 PM Matthias J. Sax 
>>> wrote:
>>>
 Jeyhun,

 thanks a lot for the KIP!

 I think there are two issues we need to address:

 (1) The KIP does not consider backward compatibility. Users did
>> complain
 about this in past releases already, and as the user base grows, we
 should not break backward compatibility in future releases anymore.
 Thus, we should think of a better way to allow key access.

 Mathieu's comment goes into the same direction

>> On the other hand, the number of compile failures that would need to
>>> be
>> fixed from this change is unfortunate. :-)

 (2) Another concern is, that there is no guard to prevent user code to
 modify the key. This might corrupt partitioning if users do alter the
 key (accidentally -- or users are just not aware that they are not
 allowed to modify the provided key object) and thus break the
 application. (This was the original motivation to not provide the key
>> in
 the first place -- it's guards against modification.)


 -Matthias



 On 5/1/17 6:31 AM, Mathieu Fenniak wrote:
> Hi Jeyhun,
>
> I just want to add my voice that, I too, have wished for access to
>> the
> record key during a mapValues or similar operation.
>
> On the other hand, the number of compile failures that would need to
>> be
> fixed from this change is unfortunate. :-)  But at least it would all
>>> be
 a
> pretty clear and easy change.
>
> Mathieu
>
>
> On Mon, May 1, 2017 at 6:55 AM, Jeyhun Karimov >>
 wrote:
>
>> Dear community,
>>
>> I want to share KIP-149 [1] based on issues KAFKA-4218 [2],
>> KAFKA-4726
 [3],
>> KAFKA-3745 [4]. The related PR can be found at [5].
>> I would like to get your comments.
>>
>> [1]
>> 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Hi Mathieu,

Thanks for feedback. I followed similar approach and updated PR and KIP
accordingly. I tried to guard the key in Processors sending a copy of an
actual key.
Because I am doing deep copy of an object, I think memory can be bottleneck
in some use-cases.

Cheers,
Jeyhun

On Tue, May 2, 2017 at 5:10 PM Mathieu Fenniak 
wrote:

> Hi Jeyhun,
>
> This approach would change ValueMapper (...etc) to be classes, rather than
> interfaces, which is also a backwards incompatible change.  An alternative
> approach that would be backwards compatible would be to define new
> interfaces, and provide overrides where those interfaces are used.
>
> Unfortunately, making the key parameter as "final" doesn't change much
> about guarding against key change.  It only prevents the parameter variable
> from being reassigned.  If the key type is a mutable object (eg. byte[]),
> it can still be mutated. (eg. key[0] = 0).  But I'm not really sure there's
> much that can be done about that.
>
> Mathieu
>
>
> On Mon, May 1, 2017 at 5:39 PM, Jeyhun Karimov 
> wrote:
>
> > Thanks for comments.
> >
> > The concerns makes sense. Although we can guard for immutable keys in
> > current implementation (with few changes), I didn't consider backward
> > compatibility.
> >
> > In this case 2 solutions come to my mind. In both cases, user accesses
> the
> > key in Object type, as passing extra type parameter will break
> > backwards-compatibility.  So user has to cast to actual key type.
> >
> > 1. Firstly, We can overload apply method with 2 argument (key and value)
> > and force key to be *final*. By doing this,  I think we can address both
> > backward-compatibility and guarding against key change.
> >
> > 2. Secondly, we can create class KeyAccess like:
> >
> > public class KeyAccess {
> > Object key;
> > public void beforeApply(final Object key) {
> > this.key = key;
> > }
> > public Object getKey() {
> > return key;
> > }
> > }
> >
> > We can extend *ValueMapper, ValueJoiner* and *ValueTransformer* from
> > *KeyAccess*. Inside processor (for example *KTableMapValuesProcessor*)
> > before calling *mapper.apply(value)* we can set the *key* by
> > *mapper.beforeApply(key)*. As a result, user can use *getKey()* to access
> > the key inside *apply(value)* method.
> >
> >
> > Cheers,
> > Jeyhun
> >
> >
> >
> >
> > On Mon, May 1, 2017 at 7:24 PM Matthias J. Sax 
> > wrote:
> >
> > > Jeyhun,
> > >
> > > thanks a lot for the KIP!
> > >
> > > I think there are two issues we need to address:
> > >
> > > (1) The KIP does not consider backward compatibility. Users did
> complain
> > > about this in past releases already, and as the user base grows, we
> > > should not break backward compatibility in future releases anymore.
> > > Thus, we should think of a better way to allow key access.
> > >
> > > Mathieu's comment goes into the same direction
> > >
> > > >> On the other hand, the number of compile failures that would need to
> > be
> > > >> fixed from this change is unfortunate. :-)
> > >
> > > (2) Another concern is, that there is no guard to prevent user code to
> > > modify the key. This might corrupt partitioning if users do alter the
> > > key (accidentally -- or users are just not aware that they are not
> > > allowed to modify the provided key object) and thus break the
> > > application. (This was the original motivation to not provide the key
> in
> > > the first place -- it's guards against modification.)
> > >
> > >
> > > -Matthias
> > >
> > >
> > >
> > > On 5/1/17 6:31 AM, Mathieu Fenniak wrote:
> > > > Hi Jeyhun,
> > > >
> > > > I just want to add my voice that, I too, have wished for access to
> the
> > > > record key during a mapValues or similar operation.
> > > >
> > > > On the other hand, the number of compile failures that would need to
> be
> > > > fixed from this change is unfortunate. :-)  But at least it would all
> > be
> > > a
> > > > pretty clear and easy change.
> > > >
> > > > Mathieu
> > > >
> > > >
> > > > On Mon, May 1, 2017 at 6:55 AM, Jeyhun Karimov  >
> > > wrote:
> > > >
> > > >> Dear community,
> > > >>
> > > >> I want to share KIP-149 [1] based on issues KAFKA-4218 [2],
> KAFKA-4726
> > > [3],
> > > >> KAFKA-3745 [4]. The related PR can be found at [5].
> > > >> I would like to get your comments.
> > > >>
> > > >> [1]
> > > >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-
> > > >> 149%3A+Enabling+key+access+in+ValueTransformer%2C+
> > > >> ValueMapper%2C+and+ValueJoiner
> > > >> [2] https://issues.apache.org/jira/browse/KAFKA-4218
> > > >> [3] https://issues.apache.org/jira/browse/KAFKA-4726
> > > >> [4] https://issues.apache.org/jira/browse/KAFKA-3745
> > > >> [5] https://github.com/apache/kafka/pull/2946
> > > >>
> > > >>
> > > >> Cheers,
> > > >> Jeyhun
> > > >>
> > > >>
> > > >>
> > > >> --
> > > >> -Cheers
> > > >>
> > > >> Jeyhun
> > > >>
> > > >
> > >
> > 

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Mathieu Fenniak]

Hi Jeyhun,

This approach would change ValueMapper (...etc) to be classes, rather than
interfaces, which is also a backwards incompatible change.  An alternative
approach that would be backwards compatible would be to define new
interfaces, and provide overrides where those interfaces are used.

Unfortunately, making the key parameter as "final" doesn't change much
about guarding against key change.  It only prevents the parameter variable
from being reassigned.  If the key type is a mutable object (eg. byte[]),
it can still be mutated. (eg. key[0] = 0).  But I'm not really sure there's
much that can be done about that.

Mathieu


On Mon, May 1, 2017 at 5:39 PM, Jeyhun Karimov  wrote:

> Thanks for comments.
>
> The concerns makes sense. Although we can guard for immutable keys in
> current implementation (with few changes), I didn't consider backward
> compatibility.
>
> In this case 2 solutions come to my mind. In both cases, user accesses the
> key in Object type, as passing extra type parameter will break
> backwards-compatibility.  So user has to cast to actual key type.
>
> 1. Firstly, We can overload apply method with 2 argument (key and value)
> and force key to be *final*. By doing this,  I think we can address both
> backward-compatibility and guarding against key change.
>
> 2. Secondly, we can create class KeyAccess like:
>
> public class KeyAccess {
> Object key;
> public void beforeApply(final Object key) {
> this.key = key;
> }
> public Object getKey() {
> return key;
> }
> }
>
> We can extend *ValueMapper, ValueJoiner* and *ValueTransformer* from
> *KeyAccess*. Inside processor (for example *KTableMapValuesProcessor*)
> before calling *mapper.apply(value)* we can set the *key* by
> *mapper.beforeApply(key)*. As a result, user can use *getKey()* to access
> the key inside *apply(value)* method.
>
>
> Cheers,
> Jeyhun
>
>
>
>
> On Mon, May 1, 2017 at 7:24 PM Matthias J. Sax 
> wrote:
>
> > Jeyhun,
> >
> > thanks a lot for the KIP!
> >
> > I think there are two issues we need to address:
> >
> > (1) The KIP does not consider backward compatibility. Users did complain
> > about this in past releases already, and as the user base grows, we
> > should not break backward compatibility in future releases anymore.
> > Thus, we should think of a better way to allow key access.
> >
> > Mathieu's comment goes into the same direction
> >
> > >> On the other hand, the number of compile failures that would need to
> be
> > >> fixed from this change is unfortunate. :-)
> >
> > (2) Another concern is, that there is no guard to prevent user code to
> > modify the key. This might corrupt partitioning if users do alter the
> > key (accidentally -- or users are just not aware that they are not
> > allowed to modify the provided key object) and thus break the
> > application. (This was the original motivation to not provide the key in
> > the first place -- it's guards against modification.)
> >
> >
> > -Matthias
> >
> >
> >
> > On 5/1/17 6:31 AM, Mathieu Fenniak wrote:
> > > Hi Jeyhun,
> > >
> > > I just want to add my voice that, I too, have wished for access to the
> > > record key during a mapValues or similar operation.
> > >
> > > On the other hand, the number of compile failures that would need to be
> > > fixed from this change is unfortunate. :-)  But at least it would all
> be
> > a
> > > pretty clear and easy change.
> > >
> > > Mathieu
> > >
> > >
> > > On Mon, May 1, 2017 at 6:55 AM, Jeyhun Karimov 
> > wrote:
> > >
> > >> Dear community,
> > >>
> > >> I want to share KIP-149 [1] based on issues KAFKA-4218 [2], KAFKA-4726
> > [3],
> > >> KAFKA-3745 [4]. The related PR can be found at [5].
> > >> I would like to get your comments.
> > >>
> > >> [1]
> > >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-
> > >> 149%3A+Enabling+key+access+in+ValueTransformer%2C+
> > >> ValueMapper%2C+and+ValueJoiner
> > >> [2] https://issues.apache.org/jira/browse/KAFKA-4218
> > >> [3] https://issues.apache.org/jira/browse/KAFKA-4726
> > >> [4] https://issues.apache.org/jira/browse/KAFKA-3745
> > >> [5] https://github.com/apache/kafka/pull/2946
> > >>
> > >>
> > >> Cheers,
> > >> Jeyhun
> > >>
> > >>
> > >>
> > >> --
> > >> -Cheers
> > >>
> > >> Jeyhun
> > >>
> > >
> >
> > --
> -Cheers
>
> Jeyhun
>

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Jeyhun Karimov]

Thanks for comments.

The concerns makes sense. Although we can guard for immutable keys in
current implementation (with few changes), I didn't consider backward
compatibility.

In this case 2 solutions come to my mind. In both cases, user accesses the
key in Object type, as passing extra type parameter will break
backwards-compatibility.  So user has to cast to actual key type.

1. Firstly, We can overload apply method with 2 argument (key and value)
and force key to be *final*. By doing this,  I think we can address both
backward-compatibility and guarding against key change.

2. Secondly, we can create class KeyAccess like:

public class KeyAccess {
Object key;
public void beforeApply(final Object key) {
this.key = key;
}
public Object getKey() {
return key;
}
}

We can extend *ValueMapper, ValueJoiner* and *ValueTransformer* from
*KeyAccess*. Inside processor (for example *KTableMapValuesProcessor*)
before calling *mapper.apply(value)* we can set the *key* by
*mapper.beforeApply(key)*. As a result, user can use *getKey()* to access
the key inside *apply(value)* method.


Cheers,
Jeyhun




On Mon, May 1, 2017 at 7:24 PM Matthias J. Sax 
wrote:

> Jeyhun,
>
> thanks a lot for the KIP!
>
> I think there are two issues we need to address:
>
> (1) The KIP does not consider backward compatibility. Users did complain
> about this in past releases already, and as the user base grows, we
> should not break backward compatibility in future releases anymore.
> Thus, we should think of a better way to allow key access.
>
> Mathieu's comment goes into the same direction
>
> >> On the other hand, the number of compile failures that would need to be
> >> fixed from this change is unfortunate. :-)
>
> (2) Another concern is, that there is no guard to prevent user code to
> modify the key. This might corrupt partitioning if users do alter the
> key (accidentally -- or users are just not aware that they are not
> allowed to modify the provided key object) and thus break the
> application. (This was the original motivation to not provide the key in
> the first place -- it's guards against modification.)
>
>
> -Matthias
>
>
>
> On 5/1/17 6:31 AM, Mathieu Fenniak wrote:
> > Hi Jeyhun,
> >
> > I just want to add my voice that, I too, have wished for access to the
> > record key during a mapValues or similar operation.
> >
> > On the other hand, the number of compile failures that would need to be
> > fixed from this change is unfortunate. :-)  But at least it would all be
> a
> > pretty clear and easy change.
> >
> > Mathieu
> >
> >
> > On Mon, May 1, 2017 at 6:55 AM, Jeyhun Karimov 
> wrote:
> >
> >> Dear community,
> >>
> >> I want to share KIP-149 [1] based on issues KAFKA-4218 [2], KAFKA-4726
> [3],
> >> KAFKA-3745 [4]. The related PR can be found at [5].
> >> I would like to get your comments.
> >>
> >> [1]
> >> https://cwiki.apache.org/confluence/display/KAFKA/KIP-
> >> 149%3A+Enabling+key+access+in+ValueTransformer%2C+
> >> ValueMapper%2C+and+ValueJoiner
> >> [2] https://issues.apache.org/jira/browse/KAFKA-4218
> >> [3] https://issues.apache.org/jira/browse/KAFKA-4726
> >> [4] https://issues.apache.org/jira/browse/KAFKA-3745
> >> [5] https://github.com/apache/kafka/pull/2946
> >>
> >>
> >> Cheers,
> >> Jeyhun
> >>
> >>
> >>
> >> --
> >> -Cheers
> >>
> >> Jeyhun
> >>
> >
>
> --
-Cheers

Jeyhun

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Matthias J. Sax]

Jeyhun,

thanks a lot for the KIP!

I think there are two issues we need to address:

(1) The KIP does not consider backward compatibility. Users did complain
about this in past releases already, and as the user base grows, we
should not break backward compatibility in future releases anymore.
Thus, we should think of a better way to allow key access.

Mathieu's comment goes into the same direction

>> On the other hand, the number of compile failures that would need to be
>> fixed from this change is unfortunate. :-)  

(2) Another concern is, that there is no guard to prevent user code to
modify the key. This might corrupt partitioning if users do alter the
key (accidentally -- or users are just not aware that they are not
allowed to modify the provided key object) and thus break the
application. (This was the original motivation to not provide the key in
the first place -- it's guards against modification.)


-Matthias



On 5/1/17 6:31 AM, Mathieu Fenniak wrote:
> Hi Jeyhun,
> 
> I just want to add my voice that, I too, have wished for access to the
> record key during a mapValues or similar operation.
> 
> On the other hand, the number of compile failures that would need to be
> fixed from this change is unfortunate. :-)  But at least it would all be a
> pretty clear and easy change.
> 
> Mathieu
> 
> 
> On Mon, May 1, 2017 at 6:55 AM, Jeyhun Karimov  wrote:
> 
>> Dear community,
>>
>> I want to share KIP-149 [1] based on issues KAFKA-4218 [2], KAFKA-4726 [3],
>> KAFKA-3745 [4]. The related PR can be found at [5].
>> I would like to get your comments.
>>
>> [1]
>> https://cwiki.apache.org/confluence/display/KAFKA/KIP-
>> 149%3A+Enabling+key+access+in+ValueTransformer%2C+
>> ValueMapper%2C+and+ValueJoiner
>> [2] https://issues.apache.org/jira/browse/KAFKA-4218
>> [3] https://issues.apache.org/jira/browse/KAFKA-4726
>> [4] https://issues.apache.org/jira/browse/KAFKA-3745
>> [5] https://github.com/apache/kafka/pull/2946
>>
>>
>> Cheers,
>> Jeyhun
>>
>>
>>
>> --
>> -Cheers
>>
>> Jeyhun
>>
> 



signature.asc
Description: OpenPGP digital signature

Re: [DISCUSS]: KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner

[Mathieu Fenniak]

Hi Jeyhun,

I just want to add my voice that, I too, have wished for access to the
record key during a mapValues or similar operation.

On the other hand, the number of compile failures that would need to be
fixed from this change is unfortunate. :-)  But at least it would all be a
pretty clear and easy change.

Mathieu


On Mon, May 1, 2017 at 6:55 AM, Jeyhun Karimov  wrote:

> Dear community,
>
> I want to share KIP-149 [1] based on issues KAFKA-4218 [2], KAFKA-4726 [3],
> KAFKA-3745 [4]. The related PR can be found at [5].
> I would like to get your comments.
>
> [1]
> https://cwiki.apache.org/confluence/display/KAFKA/KIP-
> 149%3A+Enabling+key+access+in+ValueTransformer%2C+
> ValueMapper%2C+and+ValueJoiner
> [2] https://issues.apache.org/jira/browse/KAFKA-4218
> [3] https://issues.apache.org/jira/browse/KAFKA-4726
> [4] https://issues.apache.org/jira/browse/KAFKA-3745
> [5] https://github.com/apache/kafka/pull/2946
>
>
> Cheers,
> Jeyhun
>
>
>
> --
> -Cheers
>
> Jeyhun
>