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From "Manuel Dominguez Sarmiento (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DAEMON-333) Stop abusing System.gc() on Commons Daemon jsvc shutdown
Date Wed, 03 Jun 2015 16:14:40 GMT

    [ https://issues.apache.org/jira/browse/DAEMON-333?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14571269#comment-14571269
] 

Manuel Dominguez Sarmiento commented on DAEMON-333:
---------------------------------------------------

The attached thread dump (taken while the JVM was stuck on shutdown) shows that we only have
daemon threads, and the only non-daemon, RUNNABLE threads are the Commons Loader main() and
many, many GC-related threads

> Stop abusing System.gc() on Commons Daemon jsvc shutdown
> --------------------------------------------------------
>
>                 Key: DAEMON-333
>                 URL: https://issues.apache.org/jira/browse/DAEMON-333
>             Project: Commons Daemon
>          Issue Type: Bug
>          Components: Jsvc
>    Affects Versions: 1.0.15
>            Reporter: Manuel Dominguez Sarmiento
>
> The shutdown sequence invokes System.gc() several times. I'm not sure why this would
be necessary, especially considering that System.gc() is only a hint and the JVM will not
necessarily do anything when this method is invoked. Especially if -XX:+DisableExplicitGC
is used, which is fairly common practice in production environments.
> In our case, we use rather huge heaps (over 100 GB) so shutdown can take forever, depending
on how much uncollected garbage there is in the JVM heap. We've always used -XX:+DisableExplicitGC
so this was never apparent, however we decided to stop using -XX:+DisableExplicitGC after
careful code review showed none of our apps or supporting libraries are using System.gc()
and sometimes we want to trigger GC manually from monitoring tools (Jconsole, VisualVM, etc.)
- but we found the hard way that Commons Daemon / jsvc is using System.gc() on shutdown, preventing
the speedy shutdown we were used to.



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