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From "David Bowen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-492) Global counters
Date Thu, 15 Feb 2007 20:25:05 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12473496
] 

David Bowen commented on HADOOP-492:
------------------------------------

I like the enum approach.  It solves the namespace problem, and provides compile-time checking
of the counter names.

The only possible drawback I can see is the need to send longer strings between processes.
 I have no idea if this would be a significant performance issue.  If it is, we could potentially
optimize the wire format by having a way to specify what the counters are in the job configuration,
so that the counter names never have to be sent.

> 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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