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https://issues.apache.org/jira/browse/HADOOP-10090?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13824041#comment-13824041
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Luke Lu commented on HADOOP-10090:
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I now recalled some hesitation of extra lock on source:
* It could adversely affect the application performance buy holding the source
lock while doing a snapshot. Currently source have a choice on whether and how
the snapshot should be synchronized or not depending on the nature of the
metrics involved. In many cases, source is implemented by a real object the has
application locking logic. Holding a lock doing a potentially large snapshot
(many metrics) _could_ increase lock contention significantly.
* Locking far away from the object is consider an anti-pattern that makes it
hard to reason about locking by looking at the source only.
bq. do you think we should backport YARN-1043? Looks like an incompatible
change so not sure whether we want it back to 1.0 line.
Always update all should be a compatible change, semantic wise, besides extra
objects for non-changing metrics. It seems that simply backporting the one
line change (all is true always) from YARN-1043 (and keeping the test) is less
risky to change the locking mechanisms.
> 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: HADOOP-10090.branch-1.2.patch,
> HADOOP-10090.branch-1.patch, 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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