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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11274) ConcurrentModificationException in Configuration Copy Constructor
Date Fri, 07 Nov 2014 00:52:34 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11274?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14201316#comment-14201316
] 

Hadoop QA commented on HADOOP-11274:
------------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12680005/HADOOP-11274.003.patch
  against trunk revision 75b820c.

    {color:green}+1 @author{color}.  The patch does not contain any @author tags.

    {color:red}-1 tests included{color}.  The patch doesn't appear to include any new or modified
tests.
                        Please justify why no new tests are needed for this patch.
                        Also please list what manual steps were performed to verify this patch.

    {color:green}+1 javac{color}.  The applied patch does not increase the total number of
javac compiler warnings.

    {color:green}+1 javadoc{color}.  There were no new javadoc warning messages.

    {color:green}+1 eclipse:eclipse{color}.  The patch built with eclipse:eclipse.

    {color:green}+1 findbugs{color}.  The patch does not introduce any new Findbugs (version
2.0.3) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase the total number
of release audit warnings.

    {color:green}+1 core tests{color}.  The patch passed unit tests in hadoop-common-project/hadoop-common.

    {color:green}+1 contrib tests{color}.  The patch passed contrib unit tests.

Test results: https://builds.apache.org/job/PreCommit-HADOOP-Build/5044//testReport/
Console output: https://builds.apache.org/job/PreCommit-HADOOP-Build/5044//console

This message is automatically generated.

> ConcurrentModificationException in Configuration Copy Constructor
> -----------------------------------------------------------------
>
>                 Key: HADOOP-11274
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11274
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: conf
>            Reporter: Junping Du
>            Assignee: Junping Du
>            Priority: Blocker
>         Attachments: HADOOP-11274-v2.patch, HADOOP-11274.003.patch, HADOOP-11274.patch
>
>
> Exception as below happens in doing some configuration update in parallel:
> {noformat}
> java.util.ConcurrentModificationException
> 	at java.util.HashMap$HashIterator.nextEntry(HashMap.java:922)
> 	at java.util.HashMap$EntryIterator.next(HashMap.java:962)
> 	at java.util.HashMap$EntryIterator.next(HashMap.java:960)
> 	at java.util.HashMap.putAllForCreate(HashMap.java:554)
> 	at java.util.HashMap.<init>(HashMap.java:298)
> 	at org.apache.hadoop.conf.Configuration.<init>(Configuration.java:703)
> {noformat}
> In a constructor of Configuration - public Configuration(Configuration other), the copy
of updatingResource data structure in copy constructor is not synchronized properly. 
> Configuration.get() eventually calls loadProperty() where updatingResource gets updated.
So, whats happening here is one thread is trying to do copy of Configuration as demonstrated
in stack trace and other thread is doing Configuration.get(key) and than ConcurrentModificationException
occurs because copying of updatingResource is not synchronized in constructor. 
> We should make the update to updatingResource get synchronized, and also fix other tiny
synchronized issues there.



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