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https://issues.apache.org/jira/browse/HBASE-17471?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15999500#comment-15999500
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Hudson commented on HBASE-17471:
--------------------------------

SUCCESS: Integrated in Jenkins build HBase-1.4 #725 (See 
[https://builds.apache.org/job/HBase-1.4/725/])
HBASE-17471 Region Seqid will be out of order in WAL if using (liyu: rev 
9a97e28bdf202ea2a8cadffbb8f8de4c1411447e)
* (edit) 
hbase-server/src/test/java/org/apache/hadoop/hbase/coprocessor/TestWALObserver.java
* (edit) 
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegion.java
* (edit) 
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestWALReplay.java
* (edit) 
hbase-server/src/test/java/org/apache/hadoop/hbase/wal/TestWALFactory.java
* (edit) 
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestFSHLog.java
* (edit) 
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/wal/TestWALActionsListener.java
* (edit) 
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/MultiVersionConcurrencyControl.java
* (edit) 
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/FSWALEntry.java
* (edit) 
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java
* (edit) 
hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/wal/FSHLog.java
* (edit) 
hbase-server/src/test/java/org/apache/hadoop/hbase/wal/TestSecureWAL.java
* (edit) hbase-server/src/main/java/org/apache/hadoop/hbase/wal/WALKey.java
* (edit) 
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestWALLockup.java


> Region Seqid will be out of order in WAL if using mvccPreAssign
> ---------------------------------------------------------------
>
>                 Key: HBASE-17471
>                 URL: https://issues.apache.org/jira/browse/HBASE-17471
>             Project: HBase
>          Issue Type: Bug
>          Components: wal
>    Affects Versions: 2.0.0, 1.4.0
>            Reporter: Allan Yang
>            Assignee: Allan Yang
>            Priority: Critical
>         Attachments: HBASE-17471-branch-1.v0.patch, 
> HBASE-17471-branch-1.v1.patch, HBASE-17471-branch-1.v2.patch, 
> HBASE-17471-branch-1.v3.patch, HBASE-17471-duo.patch, 
> HBASE-17471-duo-v1.patch, HBASE-17471-duo-v2.patch, HBASE-17471.patch, 
> HBASE-17471.tmp, HBASE-17471.v2.patch, HBASE-17471.v3.patch, 
> HBASE-17471.v4.patch, HBASE-17471.v5.patch, HBASE-17471.v6.patch
>
>
>  mvccPreAssign was brought by HBASE-16698, which truly improved the 
> performance of writing, especially in ASYNC_WAL scenario. But mvccPreAssign 
> was only used in {{doMiniBatchMutate}}, not in Increment/Append path. If 
> Increment/Append and batch put are using against the same region in parallel, 
> then seqid of the same region may not monotonically increasing in the WAL. 
> Since one write path acquires mvcc/seqid before append, and the other 
> acquires in the append/sync consume thread.
> The out of order situation can easily reproduced by a simple UT, which was 
> attached in the attachment. I modified the code to assert on the disorder: 
> {code}
>     if(this.highestSequenceIds.containsKey(encodedRegionName)) {
>       assert highestSequenceIds.get(encodedRegionName) < sequenceid;
>     }
> {code}
> I'd like to say, If we allow disorder in WALs, then this is not a issue. 
> But as far as I know, if {{highestSequenceIds}} is not properly set, some 
> WALs may not archive to oldWALs correctly.
> which I haven't figure out yet is that, will disorder in WAL cause data loss 
> when recovering from disaster? If so, then it is a big problem need to be 
> fixed.
> I have fix this problem in our costom1.1.x branch, my solution is using 
> mvccPreAssign everywhere, making it un-configurable. Since mvccPreAssign it 
> is indeed a better way than assign seqid in the ringbuffer thread while 
> keeping handlers waiting for it.
> If anyone think it is doable, then I will port it to branch-1 and master 
> branch and upload it. 
>  



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