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From "Jingyun Tian (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-19358) Improve the stability of splitting log when do fail over
Date Fri, 05 Jan 2018 10:35:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-19358?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16312898#comment-16312898

Jingyun Tian commented on HBASE-19358:

[~carp84] update a patch for branch-2. Sorry for my mistake.. have to remove my imgs again:(

> Improve the stability of splitting log when do fail over
> --------------------------------------------------------
>                 Key: HBASE-19358
>                 URL: https://issues.apache.org/jira/browse/HBASE-19358
>             Project: HBase
>          Issue Type: Improvement
>          Components: MTTR
>    Affects Versions: 0.98.24
>            Reporter: Jingyun Tian
>            Assignee: Jingyun Tian
>             Fix For: 2.0.0, 3.0.0, 1.4.1, 1.5.0
>         Attachments: HBASE-18619-branch-2-v2.patch, HBASE-19358-branch-1-v2.patch, HBASE-19358-branch-1-v3.patch,
HBASE-19358-branch-1.patch, HBASE-19358-branch-2-v3.patch, HBASE-19358-v1.patch, HBASE-19358-v4.patch,
HBASE-19358-v5.patch, HBASE-19358-v6.patch, HBASE-19358-v7.patch, HBASE-19358-v8.patch, HBASE-19358.patch
> The way we splitting log now is like the following figure:
> !https://issues.apache.org/jira/secure/attachment/12904506/split-logic-old.jpg!
> The problem is the OutputSink will write the recovered edits during splitting log, which
means it will create one WriterAndPath for each region and retain it until the end. If the
cluster is small and the number of regions per rs is large, it will create too many HDFS streams
at the same time. Then it is prone to failure since each datanode need to handle too many
> Thus I come up with a new way to split log.  
> !https://issues.apache.org/jira/secure/attachment/12904507/split-logic-new.jpg!
> We try to cache all the recovered edits, but if it exceeds the MaxHeapUsage, we will
pick the largest EntryBuffer and write it to a file (close the writer after finish). Then
after we read all entries into memory, we will start a writeAndCloseThreadPool, it starts
a certain number of threads to write all buffers to files. Thus it will not create HDFS streams
more than *_hbase.regionserver.hlog.splitlog.writer.threads_* we set.
> The biggest benefit is we can control the number of streams we create during splitting
> it will not exceeds *_hbase.regionserver.wal.max.splitters * hbase.regionserver.hlog.splitlog.writer.threads_*,
but before it is *_hbase.regionserver.wal.max.splitters * the number of region the hlog contains_*.

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