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https://issues.apache.org/jira/browse/FLINK-7606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16170001#comment-16170001
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Matteo Ferrario commented on FLINK-7606:
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Hi [~kkl0u],
thanks for your reply.
If I understand correctly, in processing time the state of NestedMapsStateTable
object is never cleared, while in event time at each watermark it is checked
the condition if the NFA is empty and then state is cleared.
If this consideration is correct, the memory leak (in terms of
NestedMapsStateTable that grows up without been cleared) will not occur setting
the stream time characteristic as event time:
{code:java}
env.setStreamTimeCharacteristic(TimeCharacteristic.EventTime);
{code}
On the other hand, this memory leak will occur setting the stream time
characteristic as processing time:
{code:java}
env.setStreamTimeCharacteristic(TimeCharacteristic.ProcessingTime);
{code}
Is it correct?
> 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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