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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 Mon, 10 Dec 2012 20:55:22 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7205?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13528274#comment-13528274
] 

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

[~tedyu@apache.org] 

http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/util/concurrent/CopyOnWriteArrayList.java#956
See - the iterator is a COWIterator 
documented in javadoc :
{quote}Traversal via iterators is fast and cannot encounter interference from other threads.
Iterators rely on unchanging snapshots of the array at the time the iterators were constructed.{quote}

compared to :
http://grepcode.com/file/repo1.maven.org/maven2/org.apache.hbase/hbase/0.94.1/org/apache/hadoop/hbase/util/SortedCopyOnWriteSet.java#77
which returns a TreeSet iterator known not be thread-safe in java collections


@Stack - you eagle eye - is this what you were referring to when you asked about the safeness
of the iterator?
                
> 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-v10.txt, 7205-v1.txt, 7205-v3.txt, 7205-v4.txt, 7205-v5.txt,
7205-v6.txt, 7205-v7.txt, 7205-v8.txt, 7205-v9.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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