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From Konstantin Knauf <konstantin.kn...@tngtech.com>
Subject Re: Queryable State and Windows
Date Sun, 26 Feb 2017 18:53:10 GMT
I just want to add another workaround, which does not need a
self-compiled version. You can use TimeWindow with a CountTriger.of(1)
combined with a FoldFunction for pre-aggregration and a
RichWindowFunction to update the queryable state. Additionally, you need
a TimeWindow for the final results. So you are doubling the amount of
state as well as computation, but depending on the circumstances this
might be preferrable than tweaking Flink 1.2.

I think, Jamie Grier did this similarly in one of his presentation on
the topic.



On 23.01.2017 15:39, Ufuk Celebi wrote:
> This is not possible at the moment. We discussed this a couple of
> times before, but in the end did not want to expose it with the
> initial version, because the interfaces are still very raw. This is
> definitely on the agenda though.
> As a work around you would have to build a custom Flink version with
> calls `setQueryable` on the state descriptors of the WindowOperator.
> If there is an easy non intrusive way to activate this for the
> upcoming 1.2 version, I will try to do it.
> On Mon, Jan 23, 2017 at 2:46 PM, Joe Olson <technology@nododos.com> wrote:
>> From what I've read in the documentation, and from the examples I've seen,
>> in order to make state queryable externally to Flink, the state descriptor
>> variables need access to the Flink runtime context.
>> This means the stream processor has to have access to the 'Rich' level
>> objects - 'RichFlatMap' for example. All the SNAPSHOT1.2 queryable state
>> examples I have seen revolve around RichFlatMap.
>> Is there a way to get the runtime context exposed so that you can have state
>> descriptor variables queryable from within a Flink window, while the window
>> is loading?
>> My processor is built around the following:
>> .addSource(new FlinkKafkaConsumer010())
>> .assignTimestampsAndWatermarks(new MyTimestampsAndWatermarks())
>> .keyBy()
>> .window(GlobalWindows.create())
>> .trigger(new myTrigger())
>> .apply(new myWindowFunction())
>> .addSink(new mySink())
>> The only rich object in this chain are available in the apply
>> (RichWindowFunction). But that is too late - I want to be able to query out
>> whats in the window while it is filling. I know I have access to onElement
>> in the trigger, and I can set up the state descriptor variables there, but
>> the variables don't seem to have exposure to the runtime environment within
>> the trigger.
>> Is there a way to get queryable state within a Flink window while it is
>> filling?

Konstantin Knauf * konstantin.knauf@tngtech.com * +49-174-3413182
TNG Technology Consulting GmbH, Betastr. 13a, 85774 Unterföhring
Geschäftsführer: Henrik Klagges, Christoph Stock, Dr. Robert Dahlke
Sitz: Unterföhring * Amtsgericht München * HRB 135082

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