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https://issues.apache.org/jira/browse/HIVE-17586?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16181919#comment-16181919
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Xuefu Zhang commented on HIVE-17586:
------------------------------------
Actually no according java doc at
https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ThreadPoolExecutor.html:
{quote}
If the pool currently has more than corePoolSize threads, excess threads will
be terminated if they have been idle for more than the keepAliveTime (see
getKeepAliveTime(java.util.concurrent.TimeUnit)).
{quote}
Because we use fixed pool size, there are no "excess threads" to idle out.
> Make HS2 BackgroundOperationPool not fixed
> ------------------------------------------
>
> Key: HIVE-17586
> URL: https://issues.apache.org/jira/browse/HIVE-17586
> Project: Hive
> Issue Type: Bug
> Components: HiveServer2
> Affects Versions: 1.1.0
> Reporter: Xuefu Zhang
> Assignee: Xuefu Zhang
> Attachments: HIVE-17586.1.patch, HIVE-17586.patch
>
>
> Currently the threadpool for background asynchronous operatons has a fixed
> size controled by {{hive.server2.async.exec.threads}}. However, the thread
> factory supplied for this threadpool is {{ThreadFactoryWithGarbageCleanup}}
> which creates ThreadWithGarbageCleanup. Since this is a fixed threadpool, the
> thread is actually never killed, defecting the purpose of garbage cleanup as
> noted in the thread class name. On the other hand, since these threads never
> go away, significant resources such as threadlocal variables (classloaders,
> hiveconfs, etc) are holding up even if there is no operation running. This
> can lead to escalated HS2 memory usage.
> Ideally, the threadpool should not be fixed, allowing thread to die out so
> resources can be reclaimed. The existing config
> {{hive.server2.async.exec.threads}} is treated as the max, and we can add a
> min for the threadpool {{hive.server2.async.exec.min.threads}}. Default value
> for this configure is -1, which keeps the existing behavior.
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