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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-492) Global counters
Date Thu, 15 Feb 2007 20:33:06 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12473501
] 

Doug Cutting commented on HADOOP-492:
-------------------------------------

> The only possible drawback I can see is the need to send longer strings between processes.

Another approach might be to make the protocol stateful, where the first time a counter name
is sent in a session, a String is sent, and, thereafter it is only referred to by numeric
ID.  But I wouldn't worry about this right off: first let's get it working, then optimize
it.  We can also increase the update interval to decrease traffic.

> Global counters
> ---------------
>
>                 Key: HADOOP-492
>                 URL: https://issues.apache.org/jira/browse/HADOOP-492
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: mapred
>            Reporter: arkady borkovsky
>         Assigned To: David Bowen
>
> It would be nice to have map / reduce job keep aggregated counts for arbitrary events
occuring in its tasks -- the numer of records processed, the numer of exceptions of a specific
type, the number of sentences in passive voice, whatever the jobs finds useful.
> This can be implemented by tasks periodically sending <name, value> pairs to the
jobtracker (in some implementations such messages are piggy-backed on the heartbeats), so
that the job tracker stores all the latests values from each task and aggregates them on a
request.  It should also make the aggregated values available at the job end.  The value for
a task would be flushed when the task fails.
> #491 and #490 may be related to this one.

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