[jira] [Reopened] (HBASE-19358) Improve the stability of splitting log when do fail over

["Yu Li (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-19358?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Yu Li reopened HBASE-19358:
---------------------------

Reopening since this is not committed to branch-2 yet and the branch-2 v2 patch cannot apply cleanly on latest code base thus requires refactor. [~tianjingyun] please take a look, thanks.

And please correct the branch-2 patch name since now it's called "HBASE-18619-branch-2-v2"...

> 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-18619-branch-2-v2.patch, HBASE-18619-branch-2.patch, HBASE-19358-branch-1-v2.patch, HBASE-19358-branch-1-v3.patch, HBASE-19358-branch-1.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, split-1-log.png, split-logic-new.jpg, split-logic-old.jpg, split-table.png, split_test_result.png
>
>
> 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 streams.
> 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 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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