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From "Hiroshi Ikeda (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14708) Use copy on write TreeMap for region location cache
Date Thu, 29 Oct 2015 05:20:27 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14708?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14979835#comment-14979835

Hiroshi Ikeda commented on HBASE-14708:

Sorry for my wrong operation :( I just wanted to comment.

CopyOnWriteTreeMap is not required to implement Map nor ConcurrentNavigableMap, which strained
implementation breaks the intrinsic contracts of the interfaces. It is enough to prepare some

Using AtomicReference instead of synchronized for the internal map might be better (or not).

> 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: HBASE-14708-v2.patch, HBASE-14708-v3.patch, HBASE-14708-v4.patch,
HBASE-14708-v5.patch, HBASE-14708-v6.patch, HBASE-14708-v7.patch, HBASE-14708.patch, location_cache_times.pdf,
> 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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