Re: State of triggers

[Edward Capriolo]

On Sat, Mar 4, 2017 at 10:26 AM, Jeff Jirsa  wrote:

>
>
>
> > On Mar 4, 2017, at 7:06 AM, Edward Capriolo 
> wrote:
> >
> >> On Fri, Mar 3, 2017 at 12:04 PM, Jeff Jirsa  wrote:
> >>
> >> On Fri, Mar 3, 2017 at 5:40 AM, Edward Capriolo 
> >> wrote:
> >>
> >>>
> >>> I used them. I built do it yourself secondary indexes with them. They
> >> have
> >>> there gotchas, but so do all the secondary index implementations. Just
> >>> because datastax does not write about something. Lets see like 5 years
> >> ago
> >>> there was this: https://github.com/hmsonline/cassandra-triggers
> >>>
> >>>
> >> Still in use? How'd it work? Production ready? Would you still do it
> that
> >> way in 2017?
> >>
> >>
> >>> There is a fairly large divergence to what actual users do and what
> other
> >>> groups 'say' actual users do in some cases.
> >>>
> >>
> >> A lot of people don't share what they're doing (for business reasons, or
> >> because they don't think it's important, or because they don't know
> >> how/where), and that's fine but it makes it hard for anyone to know what
> >> features are used, or how well they're really working in production.
> >>
> >> I've seen a handful of "how do we use triggers" questions in IRC, and
> they
> >> weren't unreasonable questions, but seemed like a lot of pain, and more
> >> than one of those people ultimately came back and said they used some
> other
> >> mechanism (and of course, some of them silently disappear, so we have no
> >> idea if it worked or not).
> >>
> >> If anyone's actively using triggers, please don't keep it a secret.
> Knowing
> >> that they're being used would be a great way to justify continuing to
> >> maintain them.
> >>
> >> - Jeff
> >>
> >
> > "Still in use? How'd it work? Production ready? Would you still do it
> that way in 2017?"
> >
> > I mean that is a loaded question. How long has cassandra had Secondary
> > Indexes? Did they work well? Would you use them? How many times were
> they re-written?
>
> It wasn't really meant to be a loaded question; I was being sincere
>
> But I'll answer: secondary indexes suck for many use cases, but they're
> invaluable for their actual intended purpose, and I have no idea how many
> times they've been rewritten but they're production ready for their narrow
> use case (defined by cardinality).
>
> Is there a real triggers use case still? Alternative to MVs? Alternative
> to CDC? I've never implemented triggers - since you have, what's the level
> of surprise for the developer?


:) You mention alternatives/: Lets break them down.

MV:
They seem to have a lot pf promise. IE you can use them for things other
then equality searches, and I do think the CQL example with the top N high
scores is pretty useful. Then again our buddy Mr Roth has a thread named
"Rebuild / remove node with MV is inconsistent". I actually think a lot of
the use case for mv falls into the category of "something you should
actually be doing with storm". I can vibe with the concept of not needing a
streaming platform, but i KNOW storm would do this correctly. I don't want
to land on something like 2x index v1 v2 where there was fundamental flaws
at scale.(not saying this is case but the rebuild thing seems a bit scary)

CDC:
I slightly afraid of this. Rational: A extensible piece design specifically
for a close source implementation of hub and spoke replication. I have some
experience trying to "play along" with extensible things
https://issues.apache.org/jira/browse/CASSANDRA-12627
"Thus, I'm -1 on {[PropertyOrEnvironmentSeedProvider}}."

Not a rub, but I can't even get something committed using an existing
extensible interface. Heaven forbid a use case I have would want to *change*
the interface, I would probably get a -12. So I have no desire to try and
maintain a CDC implementation. I see myself falling into the same old "why
you want to do this? -1" trap.

Coordinator Triggers:
To bring things back really old-school coordinator triggers everyone always
wanted. In a nutshell, I DO believe they are easier to reason about then
MV. It is pretty basic, it happens on the coordinator there is no batchlogs
or whatever, best effort possibly requiring more nodes then as the keys
might be on different services. Actually I tend do like features like. Once
something comes on the downswing of  "software hype cycle" you know it is
pretty stable as everyone's all excited about other things.

As I said, I know I can use storm for top-n, so what is this feature? Well
I want to optimize my network transfer generally by building my batch
mutations on the server. Seems reasonable. Maybe I want to have my own
little "read before write" thing like CQL lists.

The warts, having tried it. First time i tried it found it did not work
with non batches, patched in 3 hours. Took weeks before some CQL user had
the same problem and it got fixed :) There was no dynamic stuff at the time
so it was BYO 

Re: State of triggers

[Jeff Jirsa]

> On Mar 4, 2017, at 7:06 AM, Edward Capriolo  wrote:
> 
>> On Fri, Mar 3, 2017 at 12:04 PM, Jeff Jirsa  wrote:
>> 
>> On Fri, Mar 3, 2017 at 5:40 AM, Edward Capriolo 
>> wrote:
>> 
>>> 
>>> I used them. I built do it yourself secondary indexes with them. They
>> have
>>> there gotchas, but so do all the secondary index implementations. Just
>>> because datastax does not write about something. Lets see like 5 years
>> ago
>>> there was this: https://github.com/hmsonline/cassandra-triggers
>>> 
>>> 
>> Still in use? How'd it work? Production ready? Would you still do it that
>> way in 2017?
>> 
>> 
>>> There is a fairly large divergence to what actual users do and what other
>>> groups 'say' actual users do in some cases.
>>> 
>> 
>> A lot of people don't share what they're doing (for business reasons, or
>> because they don't think it's important, or because they don't know
>> how/where), and that's fine but it makes it hard for anyone to know what
>> features are used, or how well they're really working in production.
>> 
>> I've seen a handful of "how do we use triggers" questions in IRC, and they
>> weren't unreasonable questions, but seemed like a lot of pain, and more
>> than one of those people ultimately came back and said they used some other
>> mechanism (and of course, some of them silently disappear, so we have no
>> idea if it worked or not).
>> 
>> If anyone's actively using triggers, please don't keep it a secret. Knowing
>> that they're being used would be a great way to justify continuing to
>> maintain them.
>> 
>> - Jeff
>> 
> 
> "Still in use? How'd it work? Production ready? Would you still do it that 
> way in 2017?"
> 
> I mean that is a loaded question. How long has cassandra had Secondary
> Indexes? Did they work well? Would you use them? How many times were they 
> re-written?

It wasn't really meant to be a loaded question; I was being sincere

But I'll answer: secondary indexes suck for many use cases, but they're 
invaluable for their actual intended purpose, and I have no idea how many times 
they've been rewritten but they're production ready for their narrow use case 
(defined by cardinality).

Is there a real triggers use case still? Alternative to MVs? Alternative to 
CDC? I've never implemented triggers - since you have, what's the level of 
surprise for the developer?

Re: State of triggers

[Edward Capriolo]

On Saturday, March 4, 2017, Edward Capriolo  wrote:

>
>
> On Fri, Mar 3, 2017 at 12:04 PM, Jeff Jirsa  > wrote:
>
>> On Fri, Mar 3, 2017 at 5:40 AM, Edward Capriolo > >
>> wrote:
>>
>> >
>> > I used them. I built do it yourself secondary indexes with them. They
>> have
>> > there gotchas, but so do all the secondary index implementations. Just
>> > because datastax does not write about something. Lets see like 5 years
>> ago
>> > there was this: https://github.com/hmsonline/cassandra-triggers
>> >
>> >
>> Still in use? How'd it work? Production ready? Would you still do it that
>> way in 2017?
>>
>>
>> > There is a fairly large divergence to what actual users do and what
>> other
>> > groups 'say' actual users do in some cases.
>> >
>>
>> A lot of people don't share what they're doing (for business reasons, or
>> because they don't think it's important, or because they don't know
>> how/where), and that's fine but it makes it hard for anyone to know what
>> features are used, or how well they're really working in production.
>>
>> I've seen a handful of "how do we use triggers" questions in IRC, and they
>> weren't unreasonable questions, but seemed like a lot of pain, and more
>> than one of those people ultimately came back and said they used some
>> other
>> mechanism (and of course, some of them silently disappear, so we have no
>> idea if it worked or not).
>>
>> If anyone's actively using triggers, please don't keep it a secret.
>> Knowing
>> that they're being used would be a great way to justify continuing to
>> maintain them.
>>
>> - Jeff
>>
>
> "Still in use? How'd it work? Production ready? Would you still do it that
> way in 2017?"
>
> I mean that is a loaded question. How long has cassandra had Secondary
> Indexes? Did they work well? Would you use them? How many times were they
> re-written?
>
>
>
The state if triggers imho was more about the long standing opinion that
users should not be able to inject code into cassandra.

That stance reversed and people could inject code, eventually all the
walls: sandboxes, mandate on copying a jar to every server toppled.

In the mix the secondary index implementations (that read before write (and
maybe still do)) were pitches as the supported way to do it correctly.

To be fair i would probably do this in an application server infront of c
unless the trigger had to genenerate n in the hundreds or thousands of
events.


-- 
Sorry this was sent from mobile. Will do less grammar and spell check than
usual.

Re: State of triggers

[Edward Capriolo]

On Fri, Mar 3, 2017 at 12:04 PM, Jeff Jirsa  wrote:

> On Fri, Mar 3, 2017 at 5:40 AM, Edward Capriolo 
> wrote:
>
> >
> > I used them. I built do it yourself secondary indexes with them. They
> have
> > there gotchas, but so do all the secondary index implementations. Just
> > because datastax does not write about something. Lets see like 5 years
> ago
> > there was this: https://github.com/hmsonline/cassandra-triggers
> >
> >
> Still in use? How'd it work? Production ready? Would you still do it that
> way in 2017?
>
>
> > There is a fairly large divergence to what actual users do and what other
> > groups 'say' actual users do in some cases.
> >
>
> A lot of people don't share what they're doing (for business reasons, or
> because they don't think it's important, or because they don't know
> how/where), and that's fine but it makes it hard for anyone to know what
> features are used, or how well they're really working in production.
>
> I've seen a handful of "how do we use triggers" questions in IRC, and they
> weren't unreasonable questions, but seemed like a lot of pain, and more
> than one of those people ultimately came back and said they used some other
> mechanism (and of course, some of them silently disappear, so we have no
> idea if it worked or not).
>
> If anyone's actively using triggers, please don't keep it a secret. Knowing
> that they're being used would be a great way to justify continuing to
> maintain them.
>
> - Jeff
>

"Still in use? How'd it work? Production ready? Would you still do it that
way in 2017?"

I mean that is a loaded question. How long has cassandra had Secondary
Indexes? Did they work well? Would you use them? How many times were they
re-written?