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From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (MAPREDUCE-2124) Add job counters for measuring time spent in three different phases in reducers
Date Mon, 11 Oct 2010 18:19:36 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-2124?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12919932#action_12919932
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Chris Douglas commented on MAPREDUCE-2124:
------------------------------------------

bq. This will help us identify the bottleneck of the reducers.

Will it? The shuffle phase can be delayed by the map scheduling, the sort phase is often a
noop, and the reduce phase takes whatever time it requires. Moreover, these times are also
recorded in the job history. Wouldn't parsing that- or just using Rumen to do the analysis-
be sufficient? The cost of additional framework counters in the JobTracker is pretty high...

> Add job counters for measuring time spent in three different phases in reducers
> -------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-2124
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2124
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobtracker
>    Affects Versions: 0.22.0
>            Reporter: Scott Chen
>            Assignee: Scott Chen
>            Priority: Minor
>             Fix For: 0.22.0
>
>
> We currently have SLOTS_MILLIS_REDUCES which measures the total slot time of reducer.
> It will be useful if we have
> {code}
> SLOTS_MILLIS_REDUCES_COPY
> SLOTS_MILLIS_REDUCES_SORT
> SLOTS_MILLIS_REDUCES_REDUCE
> {code}
> which measures three different phases of a reducer.
> This will help us identify the bottleneck of the reducers.

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