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https://issues.apache.org/jira/browse/HADOOP-10077?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13809871#comment-13809871
 ] 

Hadoop QA commented on HADOOP-10077:
------------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest 
attachment 
  
http://issues.apache.org/jira/secure/attachment/12611235/HADOOP-10077.001.patch
  against trunk revision .

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

    {color:green}+1 tests included{color}.  The patch appears to include 1 new 
or modified test files.

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

    {color:green}+1 javadoc{color}.  The javadoc tool did not generate any 
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 1.3.9) warnings.

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

    {color:red}-1 core tests{color}.  The patch failed these unit tests in 
hadoop-common-project/hadoop-common:

                  org.apache.hadoop.metrics2.impl.TestMetricsSystemImpl

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

Test results: 
https://builds.apache.org/job/PreCommit-HADOOP-Build/3254//testReport/
Console output: 
https://builds.apache.org/job/PreCommit-HADOOP-Build/3254//console

This message is automatically generated.

> o.a.h.s.Groups should refresh in the background
> -----------------------------------------------
>
>                 Key: HADOOP-10077
>                 URL: https://issues.apache.org/jira/browse/HADOOP-10077
>             Project: Hadoop Common
>          Issue Type: Bug
>    Affects Versions: 2.2.1
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>         Attachments: HADOOP-10077.001.patch
>
>
> {{org.apache.hadoop.security.Groups}} maintains a cache of mappings between 
> user names and sets of associated group names.  Periodically, the entries in 
> this cache expire and must be refetched from the operating system.
> Currently, this is done in the context of whatever thread happens to try to 
> access the group mapping information right after the time period expires.  
> However, this is problematic, since that thread may be holding the 
> {{FSNamesystem}} lock.  This means that if the 
> {{GroupMappingServiceProvider}} is slow, the whole NameNode may grind to a 
> halt until it finishes.  This can generate periodic load spikes or even 
> NameNode failovers.
> Instead, we should allow the refreshing of the group mappings to be done 
> asynchronously in a background thread pool.



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