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https://issues.apache.org/jira/browse/HBASE-1810?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
stack resolved HBASE-1810.
--------------------------
Resolution: Fixed
Hadoop Flags: [Reviewed]
I looked at java src. Internally, Collections.synchronizedSet, etc., use the
same mutex as is used when you do synchronized(object) where object is the
synchronizedSet, etc.
I reviewed the rest of RegionManager. regionsInTransition seems to be safely
synchronized with Mathias's patch.
Committed branch and trunk. Thanks for the patch Mathias.
> 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: 0.20.0
>
> 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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