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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3748) Flag to make tasks to send counter information only at the end of the task
Date Thu, 28 Aug 2008 06:37:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3748?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12626448#action_12626448
] 

Alejandro Abdelnur commented on HADOOP-3748:
--------------------------------------------

For 200 nodes clusters, without counters traffic the peak for pkg_in was 900 in the JT box,
with 200 counters the peak for pkg_in was 9000.

We did not see any significant CPU increase in the JT. But my thinking is that this is extra
handling should create contention in some pieces of the JT.
 
For smaller clusters it was less. It seems it non-linear, the bigger the cluster the more
pkg_in in the JT box.

Our job tests were doing nothing just idling and incrementing counters. I'm thinking on the
overheard in the JT to handle those partial counters. Other patches as trying to move work
away from the JT to the TT or even the tasks (ie committing a task ouput). In my eyes this
patch is to along the same lines, remove as much load as possible from the JT.



> Flag to make tasks to send counter information only at the end of the task
> --------------------------------------------------------------------------
>
>                 Key: HADOOP-3748
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3748
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: mapred
>         Environment: all
>            Reporter: Alejandro Abdelnur
>
> Currently counters are streaming from the task to the jobtracker as the task progresses.
If the number of counters is large this has a significant impact on the network traffic as
well as in the JobTracker load.
> The should be a flag, for example by counter-group, that indicates that the counters
are to be reported at the end of the task. By default this flag should be set to false for
all counter-groups maintaining the current behavior.

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