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From "Ming Ma (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-4265) zookeeper.KeeperException$NodeExistsException if HMaster restarts while table is being disabled
Date Sun, 28 Aug 2011 17:54:40 GMT
zookeeper.KeeperException$NodeExistsException if HMaster restarts while table is being disabled
-----------------------------------------------------------------------------------------------

                 Key: HBASE-4265
                 URL: https://issues.apache.org/jira/browse/HBASE-4265
             Project: HBase
          Issue Type: Bug
            Reporter: Ming Ma
            Assignee: Ming Ma


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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