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From "Karthik Kambatla (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-5268) Improve history server startup performance
Date Wed, 29 May 2013 18:48:20 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-5268?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Karthik Kambatla updated MAPREDUCE-5268:
----------------------------------------

    Attachment: mr-5268.patch

Updated patch to abstract out collection/size into a local utility class and minimal changes
to JobListCache.

Considered implementing a full-blown implementation of ConcurrentSkipListMapWithSize extending
ConcurrentSkipList and adding it to hadoop-common, but decided against it as that seemed a
little overboard.
                
> Improve history server startup performance
> ------------------------------------------
>
>                 Key: MAPREDUCE-5268
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5268
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: jobhistoryserver
>    Affects Versions: 0.23.7, 2.0.4-alpha
>            Reporter: Jason Lowe
>            Assignee: Karthik Kambatla
>         Attachments: mr-5268.patch, mr-5268.patch, mr-5268-prelim.patch
>
>
> The history server can easily take many minutes to startup when there are a significant
number of jobs to scan in the done directory.  However the scanning of files is not the bottleneck,
rather it's the heavy use of ConcurrentSkipListMap.size in HistoryFileManager.  
> ConcurrentSkipListMap.size is a very expensive operation, especially on maps with many
entries, as it has to scan every entry to compute the size.  We should avoid calling this
method or at least minimize its use.

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