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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4265) zookeeper.KeeperException$NodeExistsException if HMaster restarts while table is being disabled
Date Sun, 28 Aug 2011 21:42:37 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4265?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13092555#comment-13092555

Ming Ma commented on HBASE-4265:

Perhaps the regions that are in RS_ZK_REGION_CLOSED or RS_ZK_REGION_CLOSING states shouldn't
be added to AssignmentManager.regions at the first place in AssignmentManager.rebuildUserRegions?
Those regions that have been closed by RS are asked to be closed again by AssignmentManager.
Thus the states of those regions remain as CLOSING after restart.
11/08/28 14:31:23 INFO master.AssignmentManager: Region has been CLOSING for too long, this
should eventually complete or the server will expire, doing nothing

> zookeeper.KeeperException$NodeExistsException if HMaster restarts while table is being
> -----------------------------------------------------------------------------------------------
>                 Key: HBASE-4265
>                 URL: https://issues.apache.org/jira/browse/HBASE-4265
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Ming Ma
>            Assignee: Ming Ma
>             Fix For: 0.92.0
> There seems to be more than just one issue regarding the following scenario. I would
provide a fix later just for this exception.
> 1. A table is being disabled.
> 2. HMaster restarted.
> 3. At HMaster startup, it tries to transition from disabling to disabled state. It got
the following exception.
> org.apache.zookeeper.KeeperException$NodeExistsException: KeeperErrorCode = NodeExists
for /hbase/unassigned/419b902243c836c285108ba555b712fa
> 	at org.apache.zookeeper.KeeperException.create(KeeperException.java:110)
> 	at org.apache.zookeeper.KeeperException.create(KeeperException.java:42)
> 	at org.apache.zookeeper.ZooKeeper.create(ZooKeeper.java:637)
> 	at org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper.createNonSequential(RecoverableZooKeeper.java:475)
> 	at org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper.create(RecoverableZooKeeper.java:457)
> 	at org.apache.hadoop.hbase.zookeeper.ZKUtil.createAndWatch(ZKUtil.java:742)
> 	at org.apache.hadoop.hbase.zookeeper.ZKAssign.createNodeClosing(ZKAssign.java:461)
> 	at org.apache.hadoop.hbase.master.AssignmentManager.unassign(AssignmentManager.java:1440)
> 	at org.apache.hadoop.hbase.master.AssignmentManager.unassign(AssignmentManager.java:1406)
> 	at org.apache.hadoop.hbase.master.handler.DisableTableHandler$BulkDisabler$1.run(DisableTableHandler.java:141)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> This issue is this specific region is in a special state before HMaster restarts; it
has been closed by RS properly thus the zk state is RS_ZK_REGION_CLOSED. However, HMaster
hasn't got a chance to process ClosedRegionHandler yet and thus the node remains at zk. After
RS restarts, this node is added to online region list first in AssignmentManager.rebuildUserRegions
and tries to unassign it later.

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