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https://issues.apache.org/jira/browse/HBASE-6299?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13412618#comment-13412618
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Maryann Xue commented on HBASE-6299:
------------------------------------
bq. I'm not sure what synchronize does. I suppose it prevents double assign
The interesting thing is we check RegionState is OFFLINE or CLOSED before
setting OFFLINE in zk and abort if the check fails; while we allow any
RegionState before setting RegionState OFFLINE. And since this synchronize on
RegionState does not guard the whole process (state change from PEND_OPEN to
OPENED), double assignment is not prevented at all, though there's some check
in setOfflineInZookeeper, but only when hijack=true.
So far i've seen two error cases with double assign:
1. HBASE-5816: The second assign comes in almost at the same time with the
first assignment,but gets locked by sychronized(state). After the first
assignment succeeds with sendRegionOpen() and exits the synchronized block, the
second assignment goes into the block and calls setOfflineInZookeeper() which
fails the "RegionState Offline" check and leads to master abort.
2. The second assignment kicks in after the first assignment succeeded and
deleted the ZK node but before regionOnline() is called (which removes the
region from AM.regionsInTransition and adds the region to AM.regions). The
second assignment starts a normal assign process, setting RegionState OFFLINE,
setting ZK OFFLINE, and calls sendRegionOpen() to the same dest RS. Then, when
the first assignment calls AM.regionOnline(), this region get removed from
AM.regionsInTranistion. This is a double assignment to the RS. if RS chooses to
cleanUpFailedOpen() as in 0.90, this region will be served nowhere and does not
even exist in master's regionsInTransition; if RS chooses to proceed on with
openRegion() as in trunk, master will get RS events "OPENING", "OPENED" related
to NO RegionState, as in HBASE-6300.
I can see we check if ZK node exists in setOfflineInZookeeper to prevent double
assignment, but this check is only effective when hijack=true.
Is it possible that we can do something in an earlier stage to prevent double
assignment? like in forceRegionStateToOffline()?
bq. @Mary Is HBASE-5396 committed?
No... but explicitly calling assign() from HBaseAdmin can cause the same
problem.
> RS starts region open while fails ack to HMaster.sendRegionOpen() causes
> inconsistency in HMaster's region state and a series of successive problems.
> -----------------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-6299
> URL: https://issues.apache.org/jira/browse/HBASE-6299
> Project: HBase
> Issue Type: Bug
> Components: master
> Affects Versions: 0.90.6, 0.94.0
> Reporter: Maryann Xue
> Assignee: Maryann Xue
> Priority: Critical
> Attachments: HBASE-6299-v2.patch, HBASE-6299.patch
>
>
> 1. HMaster tries to assign a region to an RS.
> 2. HMaster creates a RegionState for this region and puts it into
> regionsInTransition.
> 3. In the first assign attempt, HMaster calls RS.openRegion(). The RS
> receives the open region request and starts to proceed, with success
> eventually. However, due to network problems, HMaster fails to receive the
> response for the openRegion() call, and the call times out.
> 4. HMaster attemps to assign for a second time, choosing another RS.
> 5. But since the HMaster's OpenedRegionHandler has been triggered by the
> region open of the previous RS, and the RegionState has already been removed
> from regionsInTransition, HMaster finds invalid and ignores the unassigned ZK
> node "RS_ZK_REGION_OPENING" updated by the second attempt.
> 6. The unassigned ZK node stays and a later unassign fails coz
> RS_ZK_REGION_CLOSING cannot be created.
> {code}
> 2012-06-29 07:03:38,870 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Using pre-existing plan for
> region
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.;
>
> plan=hri=CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.,
> src=swbss-hadoop-004,60020,1340890123243,
> dest=swbss-hadoop-006,60020,1340890678078
> 2012-06-29 07:03:38,870 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Assigning region
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> to swbss-hadoop-006,60020,1340890678078
> 2012-06-29 07:03:38,870 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling
> transition=M_ZK_REGION_OFFLINE, server=swbss-hadoop-002:60000,
> region=b713fd655fa02395496c5a6e39ddf568
> 2012-06-29 07:06:28,882 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling
> transition=RS_ZK_REGION_OPENING, server=swbss-hadoop-006,60020,1340890678078,
> region=b713fd655fa02395496c5a6e39ddf568
> 2012-06-29 07:06:32,291 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling
> transition=RS_ZK_REGION_OPENING, server=swbss-hadoop-006,60020,1340890678078,
> region=b713fd655fa02395496c5a6e39ddf568
> 2012-06-29 07:06:32,299 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling
> transition=RS_ZK_REGION_OPENED, server=swbss-hadoop-006,60020,1340890678078,
> region=b713fd655fa02395496c5a6e39ddf568
> 2012-06-29 07:06:32,299 DEBUG
> org.apache.hadoop.hbase.master.handler.OpenedRegionHandler: Handling OPENED
> event for
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> from serverName=swbss-hadoop-006,60020,1340890678078, load=(requests=518945,
> regions=575, usedHeap=15282, maxHeap=31301); deleting unassigned node
> 2012-06-29 07:06:32,299 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
> master:60000-0x2377fee2ae80007 Deleting existing unassigned node for
> b713fd655fa02395496c5a6e39ddf568 that is in expected state RS_ZK_REGION_OPENED
> 2012-06-29 07:06:32,301 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
> master:60000-0x2377fee2ae80007 Successfully deleted unassigned node for
> region b713fd655fa02395496c5a6e39ddf568 in expected state RS_ZK_REGION_OPENED
> 2012-06-29 07:06:32,301 DEBUG
> org.apache.hadoop.hbase.master.handler.OpenedRegionHandler: The master has
> opened the region
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> that was online on serverName=swbss-hadoop-006,60020,1340890678078,
> load=(requests=518945, regions=575, usedHeap=15282, maxHeap=31301)
> 2012-06-29 07:07:41,140 WARN
> org.apache.hadoop.hbase.master.AssignmentManager: Failed assignment of
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> to serverName=swbss-hadoop-006,60020,1340890678078, load=(requests=0,
> regions=575, usedHeap=0, maxHeap=0), trying to assign elsewhere instead;
> retry=0
> java.net.SocketTimeoutException: Call to /172.16.0.6:60020 failed on socket
> timeout exception: java.net.SocketTimeoutException: 120000 millis timeout
> while waiting for channel to be ready for read. ch :
> java.nio.channels.SocketChannel[connected local=/172.16.0.2:53765
> remote=/172.16.0.6:60020]
> at
> org.apache.hadoop.hbase.ipc.HBaseClient.wrapException(HBaseClient.java:805)
> at org.apache.hadoop.hbase.ipc.HBaseClient.call(HBaseClient.java:778)
> at
> org.apache.hadoop.hbase.ipc.HBaseRPC$Invoker.invoke(HBaseRPC.java:283)
> at $Proxy8.openRegion(Unknown Source)
> at
> org.apache.hadoop.hbase.master.ServerManager.sendRegionOpen(ServerManager.java:573)
> at
> org.apache.hadoop.hbase.master.AssignmentManager.assign(AssignmentManager.java:1127)
> at
> org.apache.hadoop.hbase.master.AssignmentManager.assign(AssignmentManager.java:912)
> at
> org.apache.hadoop.hbase.master.AssignmentManager.assign(AssignmentManager.java:892)
> at
> org.apache.hadoop.hbase.master.handler.ClosedRegionHandler.process(ClosedRegionHandler.java:92)
> at
> org.apache.hadoop.hbase.executor.EventHandler.run(EventHandler.java:162)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> at java.lang.Thread.run(Thread.java:662)
> Caused by: java.net.SocketTimeoutException: 120000 millis timeout while
> waiting for channel to be ready for read. ch :
> java.nio.channels.SocketChannel[connected local=/172.16.0.2:53765
> remote=/172.16.0.6:60020]
> at
> org.apache.hadoop.net.SocketIOWithTimeout.doIO(SocketIOWithTimeout.java:164)
> at
> org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:155)
> at
> org.apache.hadoop.net.SocketInputStream.read(SocketInputStream.java:128)
> at java.io.FilterInputStream.read(FilterInputStream.java:116)
> at
> org.apache.hadoop.hbase.ipc.HBaseClient$Connection$PingInputStream.read(HBaseClient.java:301)
> at java.io.BufferedInputStream.fill(BufferedInputStream.java:218)
> at java.io.BufferedInputStream.read(BufferedInputStream.java:237)
> at java.io.DataInputStream.readInt(DataInputStream.java:370)
> at
> org.apache.hadoop.hbase.ipc.HBaseClient$Connection.receiveResponse(HBaseClient.java:541)
> at
> org.apache.hadoop.hbase.ipc.HBaseClient$Connection.run(HBaseClient.java:479)
> 2012-06-29 07:07:41,142 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: No previous transition plan
> was found (or we are ignoring an existing plan) for
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> so generated a random one;
> hri=CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.,
> src=, dest=swbss-hadoop-164,60020,1340888346294; 15 (online=15,
> exclude=serverName=swbss-hadoop-006,60020,1340890678078, load=(requests=0,
> regions=575, usedHeap=0, maxHeap=0)) available servers
> 2012-06-29 07:07:41,142 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign:
> master:60000-0x2377fee2ae80007 Creating (or updating) unassigned node for
> b713fd655fa02395496c5a6e39ddf568 with OFFLINE state
> 2012-06-29 07:07:41,145 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Using pre-existing plan for
> region
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.;
>
> plan=hri=CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.,
> src=, dest=swbss-hadoop-164,60020,1340888346294
> 2012-06-29 07:07:41,145 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Assigning region
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> to swbss-hadoop-164,60020,1340888346294
> 2012-06-29 07:07:41,149 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling
> transition=RS_ZK_REGION_OPENING, server=swbss-hadoop-164,60020,1340888346294,
> region=b713fd655fa02395496c5a6e39ddf568
> 2012-06-29 07:07:41,150 WARN
> org.apache.hadoop.hbase.master.AssignmentManager: Received OPENING for region
> b713fd655fa02395496c5a6e39ddf568 from server
> swbss-hadoop-164,60020,1340888346294 but region was in the state null and
> not in expected PENDING_OPEN or OPENING states
> 2012-06-29 07:07:41,296 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling
> transition=RS_ZK_REGION_OPENING, server=swbss-hadoop-164,60020,1340888346294,
> region=b713fd655fa02395496c5a6e39ddf568
> 2012-06-29 07:07:41,296 WARN
> org.apache.hadoop.hbase.master.AssignmentManager: Received OPENING for region
> b713fd655fa02395496c5a6e39ddf568 from server
> swbss-hadoop-164,60020,1340888346294 but region was in the state null and
> not in expected PENDING_OPEN or OPENING states
> 2012-06-29 07:07:41,302 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Handling
> transition=RS_ZK_REGION_OPENED, server=swbss-hadoop-164,60020,1340888346294,
> region=b713fd655fa02395496c5a6e39ddf568
> 2012-06-29 07:07:41,302 WARN
> org.apache.hadoop.hbase.master.AssignmentManager: Received OPENED for region
> b713fd655fa02395496c5a6e39ddf568 from server
> swbss-hadoop-164,60020,1340888346294 but region was in the state null and
> not in expected PENDING_OPEN or OPENING states
> 2012-06-29 07:08:38,872 INFO org.apache.hadoop.hbase.master.HMaster: balance
> hri=CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.,
> src=swbss-hadoop-006,60020,1340890678078,
> dest=swbss-hadoop-008,60020,1340891085175
> 2012-06-29 07:08:38,872 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Starting unassignment of
> region
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> (offlining)
> 2012-06-29 07:08:47,875 DEBUG
> org.apache.hadoop.hbase.master.AssignmentManager: Sent CLOSE to
> serverName=swbss-hadoop-006,60020,1340890678078, load=(requests=0, regions=0,
> usedHeap=0, maxHeap=0) for region
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> ...
> 2012-06-29 08:04:37,681 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Regions in transition timed
> out:
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> state=PENDING_CLOSE, ts=1340926468331, server=null
> 2012-06-29 08:04:37,681 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Region has been
> PENDING_CLOSE for too long, running forced unassign again on
> region=CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> 2012-06-29 08:04:47,681 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Regions in transition timed
> out:
> CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> state=PENDING_CLOSE, ts=1340926468331, server=null
> 2012-06-29 08:04:47,682 INFO
> org.apache.hadoop.hbase.master.AssignmentManager: Region has been
> PENDING_CLOSE for too long, running forced unassign again on
> region=CDR_STATS_TRAFFIC,13184390567|20120508|17||2|3|913,1337256975556.b713fd655fa02395496c5a6e39ddf568.
> {code}
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