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https://issues.apache.org/jira/browse/HBASE-1810?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12750455#action_12750455
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stack commented on HBASE-1810:
------------------------------
hmm.... Looking at the regionsInTransistion set, I see that its synchronized
sometimes but not always (I'm talking about before Mathias's patch is applied).
Mathias's patch would seem to make sense.... Let me check java src to ensure
that same monitor is effected when you do synchronized(regionsInTransistion) as
is used when you do Collections.synchronizedSortedMap get /put
> ConcurrentModificationException in region assignment
> ----------------------------------------------------
>
> Key: HBASE-1810
> URL: https://issues.apache.org/jira/browse/HBASE-1810
> Project: Hadoop HBase
> Issue Type: Bug
> Affects Versions: 0.20.0
> Reporter: Lars George
> Assignee: Mathias Herberts
> Fix For: 0.20.1
>
> Attachments: HBASE-1810.patch
>
>
> {code}
> 2009-09-01 11:28:24,106 INFO org.apache.hadoop.ipc.HBaseServer: IPC Server
> handler 16 on 60000, call regionServerReport(address: 192.168.105.39:60020,
> startcode: 1251828463043, load: (requests=0, regions=21, usedHeap=135,
> maxHeap=4093), [Lorg.apache.hadoop.hbase.HMsg;@6556c280,
> [Lorg.apache.hadoop.hbase.HRegionInfo;@22fb957a) from 192.168.105.39:60281:
> error: java.io.IOException: java.util.ConcurrentModificationException
> java.io.IOException: java.util.ConcurrentModificationException
> at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1100)
> at java.util.TreeMap$ValueIterator.next(TreeMap.java:1145)
> at
> org.apache.hadoop.hbase.master.RegionManager.isMetaServer(RegionManager.java:837)
> at
> org.apache.hadoop.hbase.master.RegionManager.regionsAwaitingAssignment(RegionManager.java:405)
> at
> org.apache.hadoop.hbase.master.RegionManager.assignRegions(RegionManager.java:202)
> at
> org.apache.hadoop.hbase.master.ServerManager.processMsgs(ServerManager.java:481)
> at
> org.apache.hadoop.hbase.master.ServerManager.processRegionServerAllsWell(ServerManager.java:415)
> at
> org.apache.hadoop.hbase.master.ServerManager.regionServerReport(ServerManager.java:324)
> at
> org.apache.hadoop.hbase.master.HMaster.regionServerReport(HMaster.java:722)
> at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at org.apache.hadoop.hbase.ipc.HBaseRPC$Server.call(HBaseRPC.java:650)
> at
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:915)
> {code}
> and
> {code}
> 2009-09-01 11:28:25,713 INFO org.apache.hadoop.ipc.HBaseServer: IPC Server
> handler 23 on 60000, call regionServerReport(address: 192.168.105.37:60020,
> startcode: 1251828463132, load: (requests=0, regions=14, usedHeap=141,
> maxHeap=4093), [Lorg.apache.hadoop.hbase.HMsg;@68345260,
> [Lorg.apache.hadoop.hbase.HRegionInfo;@430c5212) from 192.168.105.37:35432:
> error: java.io.IOException: java.util.ConcurrentModificationException
> java.io.IOException: java.util.ConcurrentModificationException
> at java.util.TreeMap$PrivateEntryIterator.nextEntry(TreeMap.java:1100)
> at java.util.TreeMap$ValueIterator.next(TreeMap.java:1145)
> at
> org.apache.hadoop.hbase.master.RegionManager.regionsAwaitingAssignment(RegionManager.java:428)
> at
> org.apache.hadoop.hbase.master.RegionManager.assignRegions(RegionManager.java:202)
> at
> org.apache.hadoop.hbase.master.ServerManager.processMsgs(ServerManager.java:481)
> at
> org.apache.hadoop.hbase.master.ServerManager.processRegionServerAllsWell(ServerManager.java:415)
> at
> org.apache.hadoop.hbase.master.ServerManager.regionServerReport(ServerManager.java:324)
> at
> org.apache.hadoop.hbase.master.HMaster.regionServerReport(HMaster.java:722)
> at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
> at
> sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
> at java.lang.reflect.Method.invoke(Method.java:597)
> at org.apache.hadoop.hbase.ipc.HBaseRPC$Server.call(HBaseRPC.java:650)
> at
> org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:915)
> {code}
> As discussed with Mathias on IRC:
> <hbs> regionsInTransition is a synchronized map so accesses to it are
> synchronized but not looping over it
> <hbs> as stated in
> http://java.sun.com/j2se/1.5.0/docs/api/java/util/Collections.html#synchronizedMap%28java.util.Map%29
> <hbs> so there is a missing synchronized(regionsInTransition) wherever
> regionsInTransition is iterated over.
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