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Date: Wed, 5 Oct 2011 18:06:30 +0000 (UTC)
From: "ramkrishna.s.vasudevan (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-4540) OpenedRegionHandler is not
 enforcing atomicity of the operation it is performing
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    [ https://issues.apache.org/jira/browse/HBASE-4540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13121299#comment-13121299 ] 

ramkrishna.s.vasudevan commented on HBASE-4540:
-----------------------------------------------

The reason for getting the znode version for the following scenario
-> RS1 tries opening a region by transiting it to OPENED
->OpenedRegionHandler has still not processed.
-> RS1 goes down and the region is assigned to RS2.
-> RS2 has transited the node to OPENED
-> Now the OpenedRegionHandler will try to delete the znode and it will succeed thinking the region is in RS1.
-> To avoid the above scenario i have tried to use the znode version that comes along when we get the callback after transiting the node to OPENED state.
                
> OpenedRegionHandler is not enforcing atomicity of the operation it is performing
> --------------------------------------------------------------------------------
>
>                 Key: HBASE-4540
>                 URL: https://issues.apache.org/jira/browse/HBASE-4540
>             Project: HBase
>          Issue Type: Bug
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>         Attachments: HBASE-4540_1.patch
>
>
> -> OpenedRegionHandler has not yet deleted the znode of the region R1 opened by RS1.
> -> RS1 goes down.
> -> Servershutdownhandler assigns the region R1 to RS2.
> -> The znode of R1 is moved to OFFLINE state by master or OPENING state by RS2 if RS2 has started opening the region.
> -> Now the first OpenedRegionHandler tries to delete the znode thinking its in OPENED state but fails.
> -> Though it fails it removes the node from RIT and adds RS1 as the owner of R1 in master's memory.
> -> Now when RS2 completes opening the region the master is not able to open the region as already the reigon has been deleted from RIT.
> {code}
> Master
> ======
> 2011-10-05 20:49:45,301 INFO org.apache.hadoop.hbase.master.handler.ServerShutdownHandler: Finished processing of shutdown of linux146,60020,1317827727647
> 2011-10-05 20:49:54,177 DEBUG org.apache.hadoop.hbase.master.HMaster: Not running balancer because 1 region(s) in transition: {3e69d628a8bd8e9b7c5e7a2a6e03aad9=t1,,1317827883842.3e69d628a8bd8e9b7c5e7a2a6e03aad9. state=PENDING_OPEN, ts=1317827985272, server=linux76,60020,1317827746847}
> 2011-10-05 20:49:57,720 DEBUG org.apache.hadoop.hbase.master.AssignmentManager: Handling transition=M_ZK_REGION_OFFLINE, server=linux76,60000,1317827742012, region=3e69d628a8bd8e9b7c5e7a2a6e03aad9
> 2011-10-05 20:50:14,501 DEBUG org.apache.hadoop.hbase.zookeeper.ZKAssign: master:60000-0x132d3dc13090023 Deleting existing unassigned node for 3e69d628a8bd8e9b7c5e7a2a6e03aad9 that is in expected state RS_ZK_REGION_OPENED
> 2011-10-05 20:50:14,505 WARN org.apache.hadoop.hbase.zookeeper.ZKAssign: master:60000-0x132d3dc13090023 Attempting to delete unassigned node 3e69d628a8bd8e9b7c5e7a2a6e03aad9 in RS_ZK_REGION_OPENED state but node is in RS_ZK_REGION_OPENING state
> After the region is opened in RS2
> =================================
> 2011-10-05 20:50:48,066 DEBUG org.apache.hadoop.hbase.master.AssignmentManager: Handling transition=RS_ZK_REGION_OPENING, server=linux76,60020,1317827746847, region=3e69d628a8bd8e9b7c5e7a2a6e03aad9, which is more than 15 seconds late
> 2011-10-05 20:50:48,290 WARN org.apache.hadoop.hbase.master.AssignmentManager: Received OPENING for region 3e69d628a8bd8e9b7c5e7a2a6e03aad9 from server linux76,60020,1317827746847 but region was in  the state null and not in expected PENDING_OPEN or OPENING states
> 2011-10-05 20:50:53,743 DEBUG org.apache.hadoop.hbase.master.AssignmentManager: Handling transition=RS_ZK_REGION_OPENING, server=linux76,60020,1317827746847, region=3e69d628a8bd8e9b7c5e7a2a6e03aad9
> 2011-10-05 20:50:54,182 DEBUG org.apache.hadoop.hbase.master.CatalogJanitor: Scanned 1 catalog row(s) and gc'd 0 unreferenced parent region(s)
> 2011-10-05 20:50:54,397 WARN org.apache.hadoop.hbase.master.AssignmentManager: Received OPENING for region 3e69d628a8bd8e9b7c5e7a2a6e03aad9 from server linux76,60020,1317827746847 but region was in  the state null and not in expected PENDING_OPEN or OPENING states
> {code}

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