flink-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Aljoscha Krettek (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-7606) CEP operator leaks state
Date Fri, 15 Sep 2017 09:50:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-7606?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16167635#comment-16167635

Aljoscha Krettek commented on FLINK-7606:

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

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.

This message was sent by Atlassian JIRA

View raw message