[jira] [Updated] (ZOOKEEPER-2185) Document recommendation to use -XX:HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError="kill %p" for server.

["Chris Nauroth (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/ZOOKEEPER-2185?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Chris Nauroth updated ZOOKEEPER-2185:
-------------------------------------
    Attachment: ZOOKEEPER-2185.001.patch

I'm attaching a patch that sets these options in zkServer.sh and zkServer.cmd and also updates documentation.

The syntax for referring to the pid on Windows might look a little strange, so here is an explanation.  The {{%}} character is reserved in cmd syntax for referring to variables: {{%1}}, {{%2}}, etc.  We don't want cmd to try to interpret {{%p}} as a variable.  Instead, we want that literal passed right into Java, which will replace it with the pid.  To escape it, you use two {{%}} characters next to each other.  That gives us {{%%p}}.  However, we need this to survive 2 cmd invocations: once for execution of zkServer.cmd and a second time when Java executes it through {{cmd /c}}.  That means we need to double-escape, which then gives us the final result of {{%%%%p}}.

To test this, I faked a change in {{QuorumPeerMain#main}} to keep allocating memory in a tight loop until it triggered an {{OutOfMemoryError}}.  I saw that it dumped an hprof file and killed the process.  I did this test on both Linux and Windows.

> Document recommendation to use -XX:HeapDumpOnOutOfMemoryError and -XX:OnOutOfMemoryError="kill %p" for server.
> --------------------------------------------------------------------------------------------------------------
>
>                 Key: ZOOKEEPER-2185
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2185
>             Project: ZooKeeper
>          Issue Type: Improvement
>          Components: documentation
>            Reporter: Chris Nauroth
>            Assignee: Chris Nauroth
>            Priority: Minor
>         Attachments: ZOOKEEPER-2185.001.patch
>
>
> Continuing to run a server process after it runs out of memory can lead to unexpected behavior.  This issue proposes that we update documentation to recommend adding these JVM options:
> # {{-XX:HeapDumpOnOutOfMemoryError}} for help with post-mortem analysis of why the process ran out of memory.
> # {{-XX:OnOutOfMemoryError="kill %p"}} to kill the JVM process, under the assumption that a process monitor will restart it.



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