Re: Getting Key from keyBy() in ProcessFunction

[Piotr Nowojski]

I think now it’s not easily possible, however it might be a valid suggestion to 
add `OnTimerContext#getCurrentKey()` method. 

Besides using ValueState as you discussed before, as a some kind of a walk 
around you could copy and modify KeyedProcessOperator to suits your needs, but 
this would be more complicated.

Piotrek

> On 4 Feb 2018, at 20:36, Ken Krugler  wrote:
> 
> Hi Jürgen,
> 
> That makes sense to me.
> 
> Anyone from the Flink team want to comment on (a) if there is a way to get 
> the current key in the timer callback without using an explicit ValueState 
> that’s maintained in the processElement() method, and (b) if not, whether 
> that could be added to the context?
> 
> Thanks,
> 
> — Ken
> 
> 
>> On Feb 4, 2018, at 6:14 AM, Jürgen Thomann > > wrote:
>> 
>> Hi Ken,
>> 
>> thanks for your answer. You're right and I'm doing it already that way. I 
>> just hoped that I could avoid the ValueState (I'm using a MapState as well 
>> already, which does not store the key) and get the key from the provided 
>> Context of the ProcessFunction. This would avoid having the ValueState and 
>> setting it in the processElement just to know the key in the onTimer 
>> function. 
>> In the current way I have to check the ValueState for every element if the 
>> key is already set or just set it every time again the processElement method 
>> is invoked.
>> 
>> Best,
>> Jürgen
>> 
>> On 02.02.2018 18:37, Ken Krugler wrote:
>>> Hi Jürgen,
>>> 
 On Feb 2, 2018, at 6:24 AM, Jürgen Thomann >>> > wrote:
 
 Hi,
 
 I'm currently using a ProcessFunction after a keyBy() and can't find a way 
 to get the key.
>>> 
>>> Doesn’t your keyBy() take a field (position, or name) to use as the key?
>>> 
>>> So then that same field contains the key in the 
>>> ProcessFunction.processElement(in, …) parameter, yes?
>>> 
 I'm currently storing it in a ValueState within processElement
>>> 
>>> If you’re using a ValueState, then there’s one of those for each unique 
>>> key, not one for the operation.
>>> 
>>> I.e. the ValueState for key = “one” is separate from the ValueState for key 
>>> = “two”.
>>> 
>>> You typically store the key in the state so it’s accessible in the onTimer 
>>> method.
>>> 
 and set it all the time, so that I can access it in onTimer(). Is there a 
 better way to get the key? We are using Flink 1.3 at the moment.
>>> 
>>> The ValueState (what you used in processElement) that you’re accessing in 
>>> the onTimer() method is also scoped by the current key.
>>> 
>>> So assuming you stored the key in the state inside of your processElement() 
>>> call, then you should have everything you need.
>>> 
>>> — Ken
>>> 
>>> PS - Check out 
>>> https://www.slideshare.net/dataArtisans/apache-flink-training-datastream-api-processfunction
>>>  
>>> 
> --
> Ken Krugler
> http://www.scaleunlimited.com 
> custom big data solutions & training
> Hadoop, Cascading, Cassandra & Solr

Re: Getting Key from keyBy() in ProcessFunction

[Ken Krugler]

Hi Jürgen,

That makes sense to me.

Anyone from the Flink team want to comment on (a) if there is a way to get the 
current key in the timer callback without using an explicit ValueState that’s 
maintained in the processElement() method, and (b) if not, whether that could 
be added to the context?

Thanks,

— Ken


> On Feb 4, 2018, at 6:14 AM, Jürgen Thomann  
> wrote:
> 
> Hi Ken,
> 
> thanks for your answer. You're right and I'm doing it already that way. I 
> just hoped that I could avoid the ValueState (I'm using a MapState as well 
> already, which does not store the key) and get the key from the provided 
> Context of the ProcessFunction. This would avoid having the ValueState and 
> setting it in the processElement just to know the key in the onTimer 
> function. 
> In the current way I have to check the ValueState for every element if the 
> key is already set or just set it every time again the processElement method 
> is invoked.
> 
> Best,
> Jürgen
> 
> On 02.02.2018 18:37, Ken Krugler wrote:
>> Hi Jürgen,
>> 
>>> On Feb 2, 2018, at 6:24 AM, Jürgen Thomann >> > wrote:
>>> 
>>> Hi,
>>> 
>>> I'm currently using a ProcessFunction after a keyBy() and can't find a way 
>>> to get the key.
>> 
>> Doesn’t your keyBy() take a field (position, or name) to use as the key?
>> 
>> So then that same field contains the key in the 
>> ProcessFunction.processElement(in, …) parameter, yes?
>> 
>>> I'm currently storing it in a ValueState within processElement
>> 
>> If you’re using a ValueState, then there’s one of those for each unique key, 
>> not one for the operation.
>> 
>> I.e. the ValueState for key = “one” is separate from the ValueState for key 
>> = “two”.
>> 
>> You typically store the key in the state so it’s accessible in the onTimer 
>> method.
>> 
>>> and set it all the time, so that I can access it in onTimer(). Is there a 
>>> better way to get the key? We are using Flink 1.3 at the moment.
>> 
>> The ValueState (what you used in processElement) that you’re accessing in 
>> the onTimer() method is also scoped by the current key.
>> 
>> So assuming you stored the key in the state inside of your processElement() 
>> call, then you should have everything you need.
>> 
>> — Ken
>> 
>> PS - Check out 
>> https://www.slideshare.net/dataArtisans/apache-flink-training-datastream-api-processfunction
>>  
>> 
--
Ken Krugler
http://www.scaleunlimited.com
custom big data solutions & training
Hadoop, Cascading, Cassandra & Solr

Re: Getting Key from keyBy() in ProcessFunction

[Jürgen Thomann]

Hi Ken,

thanks for your answer. You're right and I'm doing it already that way. 
I just hoped that I could avoid the ValueState (I'm using a MapState as 
well already, which does not store the key) and get the key from the 
provided Context of the ProcessFunction. This would avoid having the 
ValueState and setting it in the processElement just to know the key in 
the onTimer function.


In the current way I have to check the ValueState for every element if 
the key is already set or just set it every time again the 
processElement method is invoked.


Best,
Jürgen


On 02.02.2018 18:37, Ken Krugler wrote:

Hi Jürgen,

On Feb 2, 2018, at 6:24 AM, Jürgen Thomann 
> wrote:


Hi,

I'm currently using a ProcessFunction after a keyBy() and can't find 
a way to get the key.


Doesn’t your keyBy() take a field (position, or name) to use as the key?

So then that same field contains the key in the 
ProcessFunction.processElement(in, …) parameter, yes?



I'm currently storing it in a ValueState within processElement


If you’re using a ValueState, then there’s one of those for each 
unique key, not one for the operation.


I.e. the ValueState for key = “one” is separate from the ValueState 
for key = “two”.


You typically store the key in the state so it’s accessible in the 
onTimer method.


and set it all the time, so that I can access it in onTimer(). Is 
there a better way to get the key? We are using Flink 1.3 at the moment.


The ValueState (what you used in processElement) that you’re accessing 
in the onTimer() method is also scoped by the current key.


So assuming you stored the key in the state inside of your 
processElement() call, then you should have everything you need.


— Ken

PS - Check out 
https://www.slideshare.net/dataArtisans/apache-flink-training-datastream-api-processfunction


--
Ken Krugler
http://www.scaleunlimited.com 
custom big data solutions & training
Hadoop, Cascading, Cassandra & Solr

Re: Getting Key from keyBy() in ProcessFunction

[Ken Krugler]

Hi Jürgen,

> On Feb 2, 2018, at 6:24 AM, Jürgen Thomann  > wrote:
> 
> Hi,
> 
> I'm currently using a ProcessFunction after a keyBy() and can't find a way to 
> get the key.

Doesn’t your keyBy() take a field (position, or name) to use as the key?

So then that same field contains the key in the 
ProcessFunction.processElement(in, …) parameter, yes?

> I'm currently storing it in a ValueState within processElement

If you’re using a ValueState, then there’s one of those for each unique key, 
not one for the operation.

I.e. the ValueState for key = “one” is separate from the ValueState for key = 
“two”.

You typically store the key in the state so it’s accessible in the onTimer 
method.

> and set it all the time, so that I can access it in onTimer(). Is there a 
> better way to get the key? We are using Flink 1.3 at the moment.

The ValueState (what you used in processElement) that you’re accessing in the 
onTimer() method is also scoped by the current key.

So assuming you stored the key in the state inside of your processElement() 
call, then you should have everything you need.

— Ken

PS - Check out 
https://www.slideshare.net/dataArtisans/apache-flink-training-datastream-api-processfunction
 


--
Ken Krugler
http://www.scaleunlimited.com 
custom big data solutions & training
Hadoop, Cascading, Cassandra & Solr