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From Boris Lublinsky <boris.lublin...@lightbend.com>
Subject Re: Keyed State
Date Sat, 13 Jan 2018 19:33:53 GMT
Thanks Fabian
Can you also explain a thread model?
What is the paralelization between multiple keys? Is it hash based?
And also are processElement 1 and 2 are executed on different threads?
More specifically if processElement is an order of magnitude slower then 2, will it impact
processElement 2?


Boris Lublinsky
FDP Architect
boris.lublinsky@lightbend.com
https://www.lightbend.com/

> On Jan 13, 2018, at 11:06 AM, Fabian Hueske <fhueske@gmail.com> wrote:
> 
> Yes, that is correct.
> You can treat keyed ValueState like a distributed hashmap and Flink routes all state
accesses to the entry for the key of the current record.
> 
> 2018-01-13 17:07 GMT+01:00 Boris Lublinsky <boris.lublinsky@lightbend.com <mailto:boris.lublinsky@lightbend.com>>:
> Can you, please confirm that my understanding is correct?
> I am looking at the documentation on low level joins https://ci.apache.org/projects/flink/flink-docs-release-1.4/dev/stream/operators/process_function.html#low-level-joins
<https://ci.apache.org/projects/flink/flink-docs-release-1.4/dev/stream/operators/process_function.html#low-level-joins>
> And the example there.
> When we are doing KeyBy and then Process, Flink maintains an instance per key and makes
sure that that for a given key an instance for this key is used. Correct?
> It mean that the value state for a given key is maintained by Flink and in my code I
do not need to worry about a key value.
> In my code I can use ValueState and assume that Flink will keep track of it on per key
fashion.
> 
> Boris Lublinsky
> FDP Architect
> boris.lublinsky@lightbend.com <mailto:boris.lublinsky@lightbend.com>
> https://www.lightbend.com/ <https://www.lightbend.com/>
> 


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