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https://issues.apache.org/jira/browse/HBASE-11135?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13995972#comment-13995972
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Hadoop QA commented on HBASE-11135:
-----------------------------------

{color:red}-1 overall{color}.  Here are the results of testing the latest 
attachment 
  http://issues.apache.org/jira/secure/attachment/12644499/11135v6.txt
  against trunk revision .
  ATTACHMENT ID: 12644499

    {color:green}+1 @author{color}.  The patch does not contain any @author 
tags.

    {color:green}+1 tests included{color}.  The patch appears to include 12 new 
or modified tests.

    {color:green}+1 javac{color}.  The applied patch does not increase the 
total number of javac compiler warnings.

    {color:red}-1 javadoc{color}.  The javadoc tool appears to have generated 5 
warning messages.

    {color:red}-1 findbugs{color}.  The patch appears to introduce 1 new 
Findbugs (version 1.3.9) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase 
the total number of release audit warnings.

    {color:green}+1 lineLengths{color}.  The patch does not introduce lines 
longer than 100

  {color:green}+1 site{color}.  The mvn site goal succeeds with this patch.

     {color:red}-1 core tests{color}.  The patch failed these unit tests:
                       org.apache.hadoop.hbase.regionserver.wal.TestLogRolling

Test results: 
https://builds.apache.org/job/PreCommit-HBASE-Build/9509//testReport/
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/9509//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-protocol.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/9509//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-thrift.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/9509//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-client.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/9509//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop2-compat.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/9509//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-examples.html
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https://builds.apache.org/job/PreCommit-HBASE-Build/9509//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-prefix-tree.html
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https://builds.apache.org/job/PreCommit-HBASE-Build/9509//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-common.html
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https://builds.apache.org/job/PreCommit-HBASE-Build/9509//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-server.html
Findbugs warnings: 
https://builds.apache.org/job/PreCommit-HBASE-Build/9509//artifact/trunk/patchprocess/newPatchFindbugsWarningshbase-hadoop-compat.html
Console output: 
https://builds.apache.org/job/PreCommit-HBASE-Build/9509//console

This message is automatically generated.

> Change region sequenceid generation so happens earlier in the append cycle 
> rather than just before added to file
> ----------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-11135
>                 URL: https://issues.apache.org/jira/browse/HBASE-11135
>             Project: HBase
>          Issue Type: Sub-task
>          Components: wal
>            Reporter: stack
>            Assignee: stack
>         Attachments: 11135.wip.txt, 11135v2.txt, 11135v5.txt, 11135v5.txt, 
> 11135v5.txt, 11135v6.txt
>
>
> Currently we assign the region edit/sequence id just before we put it in the 
> WAL.  We do it in the single thread that feeds from the ring buffer.  Doing 
> it at this point, we can ensure order, that the edits will be in the file in 
> accordance w/ the ordering of the region sequence id.
> But the point at which region sequence id is assigned an edit is deep down in 
> the WAL system and there is a lag between our putting an edit into the WAL 
> system and the edit actually getting its edit/sequence id.
> This lag -- "late-binding" -- complicates the unification of mvcc and region 
> sequence id, especially around async WAL writes (and, related, for no-WAL 
> writes) -- the parent for this issue (For async, how you get the edit id in 
> our system when the threads have all gone home -- unless you make them wait?)
> Chatting w/ Jeffrey Zhong yesterday, we came up with a crazypants means of 
> getting the region sequence id near-immediately.  We'll run two ringbuffers.  
> The first will mesh all handler threads and the consumer will generate ids 
> (we will have order on other side of this first ring buffer), and then if 
> async or no sync, we will just let the threads return ... updating mvcc just 
> before we let them go.  All other calls will go up on to the second ring 
> buffer to be serviced as now (batching, distribution out among the sync'ing 
> threads).  The first rb will have no friction and should turn at fast rates 
> compared to the second.  There should not be noticeable slowdown nor do I 
> foresee this refactor intefering w/ our multi-WAL plans.



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