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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-10077) o.a.h.s.Groups should refresh in the background
Date Thu, 31 Oct 2013 02:56:26 GMT

    [ 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 
  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:


    {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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