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From "Duo Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-19358) Improve the stability of splitting log when do fail over
Date Tue, 28 Nov 2017 07:26:01 GMT

    [ https://issues.apache.org/jira/browse/HBASE-19358?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16268281#comment-16268281
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Duo Zhang commented on HBASE-19358:
-----------------------------------

I think I have already filed a similar issue before... Let me find it...

> 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
>         Attachments: newLogic.jpg, previousLogic.jpg
>
>
> The way we splitting log now is like the following figure:
> !https://issues.apache.org/jira/secure/attachment/12899558/previousLogic.jpg!
> The problem is the OutputSink will write the recovered edits during splitting log, which
means it will create one WriterAndPath for each region. 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 streams.
> Thus I come up with a new way to split log.  
> !https://issues.apache.org/jira/secure/attachment/12899557/newLogic.jpg!
> We cached the recovered edits unless exceeds the memory limits we set or reach the end,
then  we have a thread pool to do the rest things: write them to files and move to the destination.
> The biggest benefit is we can control the number of streams we create during splitting
log, 
> 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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