[jira] [Updated] (FLINK-19125) Avoid memory fragmentation when running flink docker image

["Xintong Song (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-19125?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Xintong Song updated FLINK-19125:
---------------------------------
    Fix Version/s:     (was: 1.11.3)

> Avoid memory fragmentation when running flink docker image
> ----------------------------------------------------------
>
>                 Key: FLINK-19125
>                 URL: https://issues.apache.org/jira/browse/FLINK-19125
>             Project: Flink
>          Issue Type: Improvement
>          Components: Deployment / Kubernetes, Runtime / State Backends
>    Affects Versions: 1.12.0, 1.11.1
>            Reporter: Yun Tang
>            Assignee: Yun Tang
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.12.0
>
>
> This ticket tracks the problem of memory fragmentation when launching default Flink docker image.
> In FLINK-18712, user reported if he submits job with rocksDB state backend on a k8s session cluster again and again once it finished, the memory usage of task manager grows continuously until OOM killed. 
>  I reproduce this problem with official Flink docker image no matter how we use rocksDB (whether to enable managed memory or not).
> I dig into the problem and found this is due to the memory fragmentation caused by {{glibc}}, which would not return memory to kernel gracefully (please refer to [glibc bugzilla|https://sourceware.org/bugzilla/show_bug.cgi?id=15321] and [glibc manual|https://www.gnu.org/software/libc/manual/html_mono/libc.html#Freeing-after-Malloc])
> I found limiting MALLOC_ARENA_MAX to 2 could mitigate this problem (please refer to [choose-for-malloc_arena_max|https://devcenter.heroku.com/articles/tuning-glibc-memory-behavior#what-value-to-choose-for-malloc_arena_max] for more details).
> And if we choose to use jemalloc to allocate memory via rebuilding another docker image, the problem would be gone. 
> {code:java}
> apt-get -y install libjemalloc-dev
> ENV LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libjemalloc.so
> {code}
> Jemalloc intends to [emphasize fragmentation avoidance|https://github.com/jemalloc/jemalloc/wiki/Background#intended-use] and we might consider to re-factor our Dockerfile to base on jemalloc to avoid memory fragmentation.



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