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From "Jason Lowe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-742) Log aggregation causes a lot of redundant setPermission calls
Date Fri, 31 May 2013 19:49:20 GMT

    [ https://issues.apache.org/jira/browse/YARN-742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13671777#comment-13671777

Jason Lowe commented on YARN-742:

No, this is a 0.23 cluster, and YARN-24 did not go into branch-0.23.

The problem is not verifyAndCreateRemoteLogDir, rather it's createAppDir.  That unconditionally
tries to mkdir and setPermission each of the three log levels (user, user/logs, and user/logs/appID).
 The mkdir isn't so bad since it already exists, but the setPermission always occurs and that
causes a write operation on the namenode.  That's three write operations per application,
per node.  In this cluster's case, that's a lot of operations due to the average number of
nodes used by the applications and number of applications per day.
> Log aggregation causes a lot of redundant setPermission calls
> -------------------------------------------------------------
>                 Key: YARN-742
>                 URL: https://issues.apache.org/jira/browse/YARN-742
>             Project: Hadoop YARN
>          Issue Type: Bug
>          Components: nodemanager
>    Affects Versions: 0.23.7, 2.0.4-alpha
>            Reporter: Kihwal Lee
>            Assignee: Jason Lowe
> In one of our clusters, namenode RPC is spending 45% of its time on serving setPermission
calls. Further investigation has revealed that most calls are redundantly made on /mapred/logs/<user>/logs.
Also mkdirs calls are made before this.

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