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From "Adrian Muraru (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7205) Coprocessor classloader is replicated for all regions in the HRegionServer
Date Sat, 08 Dec 2012 17:13:21 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7205?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13527197#comment-13527197
] 

Adrian Muraru commented on HBASE-7205:
--------------------------------------

Ted, I don't agree with v8 patch:
{code:java}
+      cl = new CoprocessorClassLoader(paths, this.getClass().getClassLoader());
+
       try {
         implClass = cl.loadClass(className);
{code}
Imagine 3 concurrent RS_OPEN_REGION threads calling #load in parallel (this is actually happening
when a pre-split table is created/enabled).
All these threads would create 3 instances of CoprocessorClassLoader (same jar) and in turn
implClass  would be loaded from different classloaders.
That's the whole mission of this patch - and #putIfAbsent before #loadClass does the trick


P.S.
I'll try to catch this case in TestClassLoading
                
> Coprocessor classloader is replicated for all regions in the HRegionServer
> --------------------------------------------------------------------------
>
>                 Key: HBASE-7205
>                 URL: https://issues.apache.org/jira/browse/HBASE-7205
>             Project: HBase
>          Issue Type: Bug
>          Components: Coprocessors
>    Affects Versions: 0.92.2, 0.94.2
>            Reporter: Adrian Muraru
>            Assignee: Ted Yu
>            Priority: Critical
>             Fix For: 0.96.0, 0.94.4
>
>         Attachments: 7205-v1.txt, 7205-v3.txt, 7205-v4.txt, 7205-v5.txt, 7205-v6.txt,
7205-v7.txt, 7205-v8.txt, HBASE-7205_v2.patch
>
>
> HBASE-6308 introduced a new custom CoprocessorClassLoader to load the coprocessor classes
and a new instance of this CL is created for each single HRegion opened. This leads to OOME-PermGen
when the number of regions go above hundres / region server. 
> Having the table coprocessor jailed in a separate classloader is good however we should
create only one for all regions of a table in each HRS.

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