Thanks Piotr, Conceptually I understand (and use) the key'ed state quite a lot, but the implementation details are what I was looking for.
It looks like `org.apache.flink.streaming.api.operators.AbstractStreamOperator#setKeyContextElement1` is what I'm looking for though. It would be cool if there were some internals design doc however? Quite hard to dig through the code as there is a log tied to how the execution of the job actually happens. Padarn On Fri, Mar 13, 2020 at 9:43 PM Piotr Nowojski <pi...@ververica.com> wrote: > Hi, > > Please take a look for example here: > > https://ci.apache.org/projects/flink/flink-docs-stable/dev/stream/state/state.html#keyed-state > And the example in particular > > https://ci.apache.org/projects/flink/flink-docs-stable/dev/stream/state/state.html#using-managed-keyed-state > > The part about "there is a specific key implicitly in context” might be > referring to the fact, that for every instance of `CountWindowAverage` that > will be running in the cluster, user doesn’t have to set the key context > explicility. Flink will set the the key context automatically for the > `ValueState<Tuple2<Long, Long>> sum;` before any invocation of > `CountWindowAverage#flatMap` method. > > In other words, one parallel instance of `CountWindowAverage` function, > for two consecutive invocations of `CountWindowAverage#flatMap` can be > referring to different underlying value of `CountWindowAverage#sum` field. > For details you could take a look at > `org.apache.flink.streaming.api.operators.AbstractStreamOperator#setKeyContextElement1` > method and how it’s being used/implemented. > > I hope that helps. > > Piotrek > > On 13 Mar 2020, at 08:20, Padarn Wilson <pad...@gmail.com> wrote: > > Hi Users, > > I am trying to understand the details of how some aspects of Flink work. > > While understanding `keyed state` I kept coming up against a claim that `there > is a specific key implicitly in context` I would like to understand how > this works, which I'm guessing means understanding the details of the > runtime context: Is there any documentation or FLIP someone can recommend > on this? > > >
