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https://issues.apache.org/jira/browse/HADOOP-10090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13820662#comment-13820662
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Ivan Mitic commented on HADOOP-10090:
-------------------------------------
Thanks a lot Chris and Luke for commenting!
bq. How about #3: we only initialize and update the JMX cache when JMX is first
used and stops updating after a period inactivity and reinitialize and update
JMX cache upon activity. Initialize/reinitialize is a "dense" update, while
"update" means the "sparse" update with the current lastRecs mechanisms. I
think #3 is should be a fairly straightforward patch and more flexible than #1
and #2.
Luke, I'm not sure where #3 differs from #2. #2 basically says that each time
JMX is queried, if TTL has exceeded, we update the internal cache and return
the values. If TTL is not exceeded, we return the cached values. There are no
updates in scenarios where users do not query JMX (metrics system timer thread
does not trigger a cache update). We just have to make sure that when JMX is
indeed queried, the next time the timer thread runs, we poll for all metric
values (not just the ones that have changed -- I think this is the current
behavior as well).
bq. Thinking about this some more, I'm in favor of Ivan's proposal #2. This
would have the side effect of lower cache hit rate/higher frequency of pulling
metrics from their sources. From what I can tell, this is acceptable, because
JMX queries haven't been a source of bottlenecks or high load. (Others, please
comment if you know otherwise.)
Thanks Chris. I am also leaning in this direction, assuming that there aren't
any gotchas that I did not know about :)
> Jobtracker metrics not updated properly after execution of a mapreduce job
> --------------------------------------------------------------------------
>
> Key: HADOOP-10090
> URL: https://issues.apache.org/jira/browse/HADOOP-10090
> Project: Hadoop Common
> Issue Type: Bug
> Components: metrics
> Affects Versions: 1.2.1
> Reporter: Ivan Mitic
> Assignee: Ivan Mitic
> Attachments: OneBoxRepro.png
>
>
> After executing a wordcount mapreduce sample job, jobtracker metrics are not
> updated properly. Often times the response from the jobtracker has higher
> number of job_completed than job_submitted (for example 8 jobs completed and
> 7 jobs submitted).
> Issue reported by Toma Paunovic.
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