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From "Robert Joseph Evans (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-3944) JobHistory web services are slower then the UI and can easly overload the JH
Date Mon, 05 Mar 2012 19:09:58 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-3944?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13222518#comment-13222518
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Robert Joseph Evans commented on MAPREDUCE-3944:
------------------------------------------------

I forgot to address Vinod's question about where the LRU is happening.  loadedJobCache, which
holds a mapping between JobId and the CompletedJob is an instance of LinkedHashMap which I
believe removes the least recently used entry when expungeEldest returns true.  I could be
wrong about that, it may just remove the entry that has been in the list the longest.
                
> JobHistory web services are slower then the UI and can easly overload the JH
> ----------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-3944
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3944
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>    Affects Versions: 0.23.1, 0.23.2
>            Reporter: Robert Joseph Evans
>            Assignee: Robert Joseph Evans
>            Priority: Blocker
>
> When our first customer started using the Job History web services today the History
Server ground to a halt.  We found 250 Jetty threads stuck on the following stack trace.
> {noformat}
>    java.lang.Thread.State: BLOCKED (on object monitor)
>         at org.apache.hadoop.mapreduce.v2.hs.JobHistory.getJob(JobHistory.java:898)
>         - waiting to lock <0x00002aaab364ba60> (a org.apache.hadoop.mapreduce.v2.hs.JobHistory)
>         at org.apache.hadoop.mapreduce.v2.hs.webapp.HsWebServices.getJobs(HsWebServices.java:188)
> {noformat}
> HsWebServices.java:188 corresponds to the /mapreduce/jobs service.
> Looking at the code there are a number of optimizations that need to be done to improve
its performance.

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