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Posted to issues@flink.apache.org by "xiangyu feng (Jira)" <ji...@apache.org> on 2023/10/12 11:12:00 UTC

[jira] [Closed] (FLINK-32746) Using ZGC in JDK17 to solve long time class unloading STW

     [ https://issues.apache.org/jira/browse/FLINK-32746?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

xiangyu feng closed FLINK-32746.
--------------------------------
    Resolution: Done

JDK17 is already supported in https://issues.apache.org/jira/browse/FLINK-15736, user can enable ZGC by configuring by customizing the `env.java.opts.all` parameter. There already have a example in OLAP QuickStart docs：https://nightlies.apache.org/flink/flink-docs-master/docs/dev/table/olap_quickstart/

> Using ZGC in JDK17 to solve long time class unloading STW
> ---------------------------------------------------------
>
>                 Key: FLINK-32746
>                 URL: https://issues.apache.org/jira/browse/FLINK-32746
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table SQL / Runtime
>            Reporter: xiangyu feng
>            Priority: Major
>
> In a OLAP session cluster, a TM need to frequently create new classloaders and  generate new classes. These classes will be accumulated in metaspace. When metaspace data usage reaches a threshold, a FullGC with a long time Stop-the-World will be triggered. Currently, both SerialGC, ParallelGC and G1GC are doing Stop-the-World class unloading. Only ZGC supports concurrent class unload, see more in [https://bugs.openjdk.org/browse/JDK-8218905|https://bugs.openjdk.org/browse/JDK-8218905).].
>  
> In our scenario, a class unloading for a 2GB metaspace with 5million classes will stop the application more than 40 seconds. After switch to ZGC, the maximum STW of the application has been reduced to less than 10ms.
>  



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