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https://issues.apache.org/jira/browse/FLINK-7606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16192994#comment-16192994
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Kostas Kloudas commented on FLINK-7606:
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You are right!
There is already a discussion about introducing something like an "idle"
watermark, that simply advances time for inactive partitions. This will help in
some similar usecases.
Now for your case specifically, it could work only if you know that no more
elements belonging to a specific period (in event time) will come. Because if
such elements arrive, then your previous results will be incorrect, right? This
is the reason why we have not introduced such a mechanism.
> CEP operator leaks state
> ------------------------
>
> Key: FLINK-7606
> URL: https://issues.apache.org/jira/browse/FLINK-7606
> Project: Flink
> Issue Type: Bug
> Components: CEP
> Affects Versions: 1.3.1
> Reporter: Matteo Ferrario
> Attachments: heap-dump1.png, heap-dump2.png, heap-dump3.png,
> Schermata 2017-09-27 alle 00.35.53.png
>
>
> The NestedMapsStateTable grows up continuously without free the heap memory.
> We created a simple job that processes a stream of messages and uses CEP to
> generate an outcome message when a specific pattern is identified.
> The messages coming from the stream are grouped by a key defined in a
> specific field of the message.
> We've also added the "within" clause (set as 5 minutes), indicating that two
> incoming messages match the pattern only if they come in a certain time
> window.
> What we've seen is that for every key present in the message, an NFA object
> is instantiated in the NestedMapsStateTable and it is never deallocated.
> Also the "within" clause didn't help: we've seen that if we send messages
> that don't match the pattern, the memory grows up (I suppose that the state
> of NFA is updated) but it is not cleaned also after the 5 minutes of time
> window defined in "within" clause.
> If you need, I can provide more details about the job we've implemented and
> also the screenshots about the memory leak.
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