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From "Elliott Clark (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14708) Use copy on write TreeMap for region location cache
Date Tue, 27 Oct 2015 16:31:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14708?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14976674#comment-14976674
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Elliott Clark commented on HBASE-14708:
---------------------------------------

Notice that the delete location time scale is logarithmic.

> Use copy on write TreeMap for region location cache
> ---------------------------------------------------
>
>                 Key: HBASE-14708
>                 URL: https://issues.apache.org/jira/browse/HBASE-14708
>             Project: HBase
>          Issue Type: Improvement
>          Components: Client
>    Affects Versions: 1.1.2
>            Reporter: Elliott Clark
>            Assignee: Elliott Clark
>            Priority: Critical
>             Fix For: 2.0.0, 1.2.0, 1.3.0
>
>         Attachments: location_cache_times.pdf, result.csv
>
>
> Internally a co-worker profiled their application that was talking to HBase. > 60%
of the time was spent in locating a region. This was while the cluster was stable and no regions
were moving.
> To figure out if there was a faster way to cache region location I wrote up a benchmark
here: https://github.com/elliottneilclark/benchmark-hbase-cache
> This tries to simulate a heavy load on the location cache. 
> * 24 different threads.
> * 2 Deleting location data
> * 2 Adding location data
> * Using floor to get the result.
> To repeat my work just run ./run.sh and it should produce a result.csv
> Results:
> ConcurrentSkiplistMap is a good middle ground. It's got equal speed for reading and writing.
> However most operations will not need to remove or add a region location. There will
be potentially several orders of magnitude more reads for cached locations than there will
be on clearing the cache.
> So I propose a copy on write tree map.



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