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Date: Tue, 17 Jan 2012 18:32:40 +0000 (UTC)
From: "Zhihong Yu (Commented) (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-5179) Concurrent processing of
 processFaileOver and ServerShutdownHandler may cause region to be assigned
 before log splitting is completed, causing data loss
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    [ https://issues.apache.org/jira/browse/HBASE-5179?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13187863#comment-13187863 ] 

Zhihong Yu commented on HBASE-5179:
-----------------------------------

For hbase-5179v9.patch:
{code}
+      if (currentMetaServer != null
+          && this.serverManager.isServerOnline(currentMetaServer)) {
+        // Current meta server is dead, we first split its log and then expire
{code}
Is the above right ?
{code}
+        this.fileSystemManager.splitLog(currentMetaServer);
         expireIfOnline(currentMetaServer);
{code}
The splitLog() would end up calling:
{code}
  public void splitLog(final List<ServerName> serverNames) throws IOException {
{code}
If distributedLogSplitting is true, log splitting would be in progress upon return from splitLog().
We need to either disable distributedLogSplitting or introduce synchronization mechanism for above.
                
> Concurrent processing of processFaileOver and ServerShutdownHandler may cause region to be assigned before log splitting is completed, causing data loss
> --------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-5179
>                 URL: https://issues.apache.org/jira/browse/HBASE-5179
>             Project: HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 0.90.2
>            Reporter: chunhui shen
>            Assignee: chunhui shen
>            Priority: Critical
>             Fix For: 0.92.0, 0.94.0, 0.90.6
>
>         Attachments: 5179-90.txt, 5179-90v2.patch, 5179-90v3.patch, 5179-90v4.patch, 5179-90v5.patch, 5179-90v6.patch, 5179-90v7.patch, 5179-90v8.patch, 5179-90v9.patch, 5179-v2.txt, 5179-v3.txt, 5179-v4.txt, hbase-5179.patch, hbase-5179v5.patch, hbase-5179v6.patch, hbase-5179v7.patch, hbase-5179v8.patch, hbase-5179v9.patch
>
>
> If master's processing its failover and ServerShutdownHandler's processing happen concurrently, it may appear following  case.
> 1.master completed splitLogAfterStartup()
> 2.RegionserverA restarts, and ServerShutdownHandler is processing.
> 3.master starts to rebuildUserRegions, and RegionserverA is considered as dead server.
> 4.master starts to assign regions of RegionserverA because it is a dead server by step3.
> However, when doing step4(assigning region), ServerShutdownHandler may be doing split log, Therefore, it may cause data loss.

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