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https://issues.apache.org/jira/browse/KAFKA-12328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17287774#comment-17287774
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fml2 commented on KAFKA-12328:
------------------------------
I now see that a processor / transformer is inherently "not thread safe" due to
the API, in particular the method "init(context)". This implies that there
should be one processor instance per context instance.
> Expose TaskId partition number
> ------------------------------
>
> Key: KAFKA-12328
> URL: https://issues.apache.org/jira/browse/KAFKA-12328
> Project: Kafka
> Issue Type: Wish
> Components: streams
> Reporter: fml2
> Priority: Major
> Labels: needs-kip
>
> This question was posted [on
> stackoverflow|https://stackoverflow.com/questions/66032099/kafka-streams-how-to-get-the-partition-an-iterartor-is-iterating-over]
> and got an answer but the solution is quite complicated hence this ticket.
>
> In my Kafka Streams application, I have a task that sets up a scheduled (by
> the wall time) punctuator. The punctuator iterates over the entries of a
> store and does something with them. Like this:
> {code:java}
> var store = context().getStateStore("MyStore");
> var iter = store.all();
> while (iter.hasNext()) {
> var entry = iter.next();
> // ... do something with the entry
> }
> // Print a summary (now): N entries processed
> // Print a summary (wish): N entries processed in partition P
> {code}
> Is it possible to find out which partition the punctuator operates on? The
> java docs for {{ProcessorContext.partition()}} states that this method
> returns {{-1}} within punctuators.
> I've read [Kafka Streams: Punctuate vs
> Process|https://stackoverflow.com/questions/50776987/kafka-streams-punctuate-vs-process]
> and the answers there. I can understand that a task is, in general, not tied
> to a particular partition. But an iterator should be tied IMO.
> How can I find out the partition?
> Or is my assumption that a particular instance of a store iterator is tied to
> a partion wrong?
> What I need it for: I'd like to include the partition number in some log
> messages. For now, I have several nearly identical log messages stating that
> the punctuator does this and that. In order to make those messages "unique"
> I'd like to include the partition number into them.
> Since I'm working with a single store here (which might be partitioned), I
> assume that every single execution of the punctuator is bound to a single
> partition of that store.
>
> It would be cool if there were a method {{iterator.partition}} (or similar)
> to get this information.
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