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From "Hadoop QA (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-202) Log Aggregation generates a storm of fsync() for namenode
Date Tue, 06 Nov 2012 18:44:12 GMT

    [ https://issues.apache.org/jira/browse/YARN-202?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13491699#comment-13491699
] 

Hadoop QA commented on YARN-202:
--------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest attachment 
  http://issues.apache.org/jira/secure/attachment/12552193/yarn-202.patch
  against trunk revision .

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

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

Test results: https://builds.apache.org/job/PreCommit-YARN-Build/134//testReport/
Console output: https://builds.apache.org/job/PreCommit-YARN-Build/134//console

This message is automatically generated.
                
> Log Aggregation generates a storm of fsync() for namenode
> ---------------------------------------------------------
>
>                 Key: YARN-202
>                 URL: https://issues.apache.org/jira/browse/YARN-202
>             Project: Hadoop YARN
>          Issue Type: Bug
>    Affects Versions: 2.0.2-alpha, 0.23.4
>            Reporter: Kihwal Lee
>            Assignee: Kihwal Lee
>            Priority: Critical
>         Attachments: yarn-202.patch
>
>
> When the log aggregation is on, write to each aggregated container log causes hflush()
to be called. For large clusters, this can creates a lot of fsync() calls for namenode. 
> We have seen 6-7x increase in the average number of fsync operations compared to 1.0.x
on a large busy cluster. Over 99% of fsync ops were for log aggregation writing to tmp files.

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