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https://issues.apache.org/jira/browse/HBASE-13959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14700464#comment-14700464
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Nick Dimiduk commented on HBASE-13959:
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[~haridsv] mind adding a release note summarizing this change and pointing out
your new config? Thanks.
> Region splitting uses a single thread in most common cases
> ----------------------------------------------------------
>
> Key: HBASE-13959
> URL: https://issues.apache.org/jira/browse/HBASE-13959
> Project: HBase
> Issue Type: Bug
> Components: regionserver
> Affects Versions: 0.98.12
> Reporter: Hari Krishna Dara
> Assignee: Hari Krishna Dara
> Priority: Critical
> Fix For: 2.0.0, 0.98.14, 1.0.2, 1.2.0, 1.1.2, 1.3.0
>
> Attachments: 13959-0.98.txt, 13959-suggest.txt, HBASE-13959-2.patch,
> HBASE-13959-3.patch, HBASE-13959-4.patch, HBASE-13959-5.patch,
> HBASE-13959.patch, region-split-durations-compared.png
>
>
> When storefiles need to be split as part of a region split, the current logic
> uses a threadpool with the size set to the size of the number of stores.
> Since most common table setup involves only a single column family, this
> translates to having a single store and so the threadpool is run with a
> single thread. However, in a write heavy workload, there could be several
> tens of storefiles in a store at the time of splitting, and with a threadpool
> size of one, these files end up getting split sequentially.
> With a bit of tracing, I noticed that it takes on an average of 350ms to
> create a single reference file, and splitting each storefile involves
> creating two of these, so with a storefile count of 20, it takes about 14s
> just to get through this phase alone (2 reference files for each storefile),
> pushing the total time the region is offline to 18s or more. For environments
> that are setup to fail fast, this makes the client exhaust all retries and
> fail with NotServingRegionException.
> The fix should increase the concurrency of this operation.
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