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https://issues.apache.org/jira/browse/HADOOP-492?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12476907
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Albert Chern commented on HADOOP-492:
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I played around with this a bit today and I have a few questions:
1) Why does the method to increment a counter take an enum whereas the method
to read the value takes a String? Wouldn't it be more convenient if
Counters.getCounter() also took an enum?
2) As a test, I created an enum with the value MY_COUNTER and placed a call to
reporter.incrCounter(MY_COUNTER, 1) at the very beginning of a map().
Surprisingly, the final value was slightly less than MapTask's INPUT_RECORDS
(120925196 vs. 120926095). Am I missing something here, or is this potentially
a bug?
> 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
> Fix For: 0.12.0
>
> Attachments: counters1.patch, counters2.patch, counters3.patch
>
>
> 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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