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https://issues.apache.org/jira/browse/FLINK-7606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16167635#comment-16167635
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Aljoscha Krettek commented on FLINK-7606:
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How do you mean? They could get the timed-out partially matched sequences and
then all state for that key (NFA, element queue) should be cleared. Otherwise
you will also have leaks in RocksDB.
If the memory/heap backend is working correctly (as I'm assuming for the
moment) then this is not a problem of leaking memory but of leaking state, i.e.
state that is never being cleaned up. If this is the case we'll have the same
problem on any state backend, it might just be the case that we will see
problems later in RocksDB because we have more space to work with.
> 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
>
>
> 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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