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https://issues.apache.org/jira/browse/HBASE-5179?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13189277#comment-13189277
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Zhihong Yu commented on HBASE-5179:
-----------------------------------
{code}
2012-01-19 11:10:35,847 INFO
org.apache.hadoop.hbase.zookeeper.RegionServerTracker: RegionServer ephemeral
node deleted, processing expiration [C3S31,20020,1326987900492]
2012-01-19 11:10:35,850 DEBUG org.apache.hadoop.hbase.master.ServerManager:
Added=C3S31,20020,1326987900492 to dead servers, submitted shutdown handler to
be executed, root=true, meta=false
2012-01-19 11:10:35,851 INFO
org.apache.hadoop.hbase.master.handler.ServerShutdownHandler: Splitting logs
for C3S31,20020,1326987900492
...
2012-01-19 11:12:37,003 INFO
org.apache.hadoop.hbase.regionserver.wal.HLogSplitter: Archived processed log
hdfs://C3S31:9000/hbase/.logs/C3S31,20020,1326987900492/C3S31%3A20020.1326987901100
to hdfs://C3S31:9000/hbase/.oldlogs/C3S31%3A20020.1326987901100
2012-01-19 11:12:37,004 INFO
org.apache.hadoop.hbase.regionserver.wal.HLogSplitter: hlog file splitting
completed in 1137 ms for hdfs://C3S31:9000/hbase/.logs/C3S31,20020,1326987900492
2012-01-19 11:12:37,004 INFO
org.apache.hadoop.hbase.master.handler.ServerShutdownHandler: Server
C3S31,20020,1326987900492 was carrying ROOT. Trying to assign.
...
2012-01-19 11:12:37,382 INFO org.apache.hadoop.hbase.master.HMaster: .META.
assigned=2, rit=false, location=C3S32:20020
2012-01-19 11:12:37,382 INFO org.apache.hadoop.hbase.master.HMaster: Master
startup proceeding: master failover
2012-01-19 11:12:37,383 WARN org.apache.hadoop.hbase.master.AssignmentManager:
Overwriting 1028785192 on serverName=C3S32,20020,1326987400439,
load=(requests=0, regions=0, usedHeap=0, maxHeap=0)
2012-01-19 11:12:37,384 WARN org.apache.hadoop.hbase.master.AssignmentManager:
Overwriting 70236052 on serverName=C3S32,20020,1326987400439, load=(requests=0,
regions=0, usedHeap=0, maxHeap=0)
2012-01-19 11:12:37,393 INFO
org.apache.hadoop.hbase.master.handler.ServerShutdownHandler: Reassigning 0
region(s) that C3S31,20020,1326987900492 was carrying (skipping 0 regions(s)
that are already in transition)
2012-01-19 11:12:37,393 INFO
org.apache.hadoop.hbase.master.handler.ServerShutdownHandler: Finished
processing of shutdown of C3S31,20020,1326987900492
{code}
>From above log, we can see that .META. was assigned to C3S32 and log splitting
>was for C3S31.
So was there data loss ?
> 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, 5179-90v10.patch, 5179-90v11.patch,
> 5179-90v12.patch, 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-v11-92.txt, 5179-v11.txt, 5179-v2.txt, 5179-v3.txt,
> 5179-v4.txt, Errorlog, hbase-5179.patch, hbase-5179v10.patch,
> hbase-5179v12.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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