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From "Kostas Kloudas (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-7606) CEP operator leaks state
Date Fri, 15 Sep 2017 14:44:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-7606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16167954#comment-16167954

Kostas Kloudas commented on FLINK-7606:

It should be cleared. 

In event time, we do not have timers, but at each watermark the condition if the NFA is empty
is checked and if yes, then the state is cleared up. In processing time, it is true that we
are always waiting for the "next" element although this is going to change in 1.4.

I am having a look to the code and I will come back as soon as I have something. 
Sorry [~matteoferrario29] for the delayed answer but this week has been a bit busy.

> 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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