[HBASE-2781] ZKW.createUnassignedRegion doesn't make sure existing znode is in the right state

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 0.90.0
• Hadoop Flags: Reviewed
• Assignee: Karthik Ranganathan
• Reporter: Jean-Daniel Cryans
• Created: 23/Jun/10 23:43
• Updated: 20/Nov/15 12:44
• Resolved: 14/Jul/10 15:41

Description

In ZKW.createUnassignedRegion I see this comment:

      // check if this node already exists - 
      //   - it should not exist
      //   - if it does, it should be in the CLOSED state

And what I got is:

2010-06-23 15:42:05,823 INFO  [IPC Server handler 3 on 60362] master.ServerManager(457): Processing MSG_REPORT_PROCESS_OPEN: test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464. from h136.sfo.stumble.net,60365,1277332849712; 1 of 4
2010-06-23 15:42:05,867 INFO  [RegionServer:1.worker] regionserver.HRegionServer$Worker(1338): Worker: MSG_REGION_OPEN: test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
2010-06-23 15:42:05,870 DEBUG [RegionServer:1.worker] regionserver.RSZookeeperUpdater(157): Updating ZNode /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464 with [RS2ZK_REGION_OPENING] expected version = 0
2010-06-23 15:42:05,871 DEBUG [main-EventThread] master.HMaster(1158): Event NodeDataChanged with state SyncConnected with path /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:05,871 DEBUG [main-EventThread] master.ZKMasterAddressWatcher(64): Got event NodeDataChanged with path /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:05,871 DEBUG [main-EventThread] master.ZKUnassignedWatcher(95): ZK-EVENT-PROCESS: Got zkEvent NodeDataChanged state:SyncConnected path:/1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:05,872 INFO  [main-EventThread] regionserver.HRegionServer(379): Got ZooKeeper event, state: SyncConnected, type: NodeDataChanged, path: /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:05,872 DEBUG [MASTER_OPENREGION-10.10.1.136:60362-1] handler.MasterOpenRegionHandler(77): Event = RS2ZK_REGION_OPENING, region = 13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:05,874 DEBUG [RegionServer:1.worker] regionserver.HRegion(297): Creating region test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
2010-06-23 15:42:06,154 INFO  [RegionServer:1.worker] regionserver.HRegion(366): Onlined test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.; next sequenceid=1
2010-06-23 15:42:06,154 DEBUG [RegionServer:1.worker] regionserver.RSZookeeperUpdater(157): Updating ZNode /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464 with [RS2ZK_REGION_OPENED] expected version = 1\
org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:06,249 ERROR [RegionServer:1.worker] regionserver.HRegionServer(1488): Failed to mark region test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464. as opened
java.io.IOException: org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
Caused by: org.apache.zookeeper.KeeperException$ConnectionLossException: KeeperErrorCode = ConnectionLoss for /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:06,993 DEBUG [RegionServer:1] regionserver.HRegionServer(1569): closing region test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
2010-06-23 15:42:06,993 DEBUG [RegionServer:1] regionserver.HRegion(487): Closing test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.: disabling compactions & flushes
2010-06-23 15:42:06,993 DEBUG [RegionServer:1] regionserver.HRegion(512): Updates disabled for region, no outstanding scanners on test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
2010-06-23 15:42:06,993 DEBUG [RegionServer:1] regionserver.HRegion(519): No more row locks outstanding on region test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
2010-06-23 15:42:06,994 INFO  [RegionServer:1] regionserver.HRegion(531): Closed test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
2010-06-23 15:42:09,105 INFO  [master] master.ProcessServerShutdown(126): Region test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464. was in transition 
name=test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464., state=PENDING_OPEN on dead server h136.sfo.stumble.net,60365,1277332849712 - marking unassigned
2010-06-23 15:42:10,065 INFO  [IPC Server handler 2 on 60362] master.RegionManager(340): Assigning region test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464. to h136.sfo.stumble.net,60363,1277332849671
2010-06-23 15:42:10,067 DEBUG [IPC Server handler 2 on 60362] zookeeper.ZooKeeperWrapper(1079): While creating UNASSIGNED region 13bef4950ac6827ac32d87682b8b2464 exists, state = RS2ZK_REGION_OPENING
2010-06-23 15:42:10,126 WARN  [IPC Server handler 2 on 60362] zookeeper.ZooKeeperWrapper(1024): <localhost:/1,org.apache.hadoop.hbase.master.HMaster>Failed to create ZNode /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464 in ZooKeeper
org.apache.zookeeper.KeeperException$NodeExistsException: KeeperErrorCode = NodeExists for /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:10,127 DEBUG [IPC Server handler 2 on 60362] master.RegionManager(350): Created UNASSIGNED zNode test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464. in state M2ZK_REGION_OFFLINE
2010-06-23 15:42:10,245 INFO  [RegionServer:0] regionserver.HRegionServer(511): MSG_REGION_OPEN: test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
2010-06-23 15:42:11,248 INFO  [IPC Server handler 1 on 60362] master.ServerManager(457): Processing MSG_REPORT_PROCESS_OPEN: test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464. from h136.sfo.stumble.net,60363,1277332849671; 7 of 13
2010-06-23 15:42:13,795 INFO  [RegionServer:0.worker] regionserver.HRegionServer$Worker(1338): Worker: MSG_REGION_OPEN: test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
2010-06-23 15:42:13,797 ERROR [RegionServer:0.worker] regionserver.RSZookeeperUpdater(107): ZNode /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464 is not in CLOSED/OFFLINE state (state = RS2ZK_REGION_OPENING), will NOT open region.
2010-06-23 15:42:13,798 ERROR [RegionServer:0.worker] regionserver.HRegionServer(814): Error opening test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
java.io.IOException: ZNode /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464 is not in CLOSED/OFFLINE state (state = RS2ZK_REGION_OPENING), will NOT open region.
2010-06-23 15:42:13,800 ERROR [RegionServer:0.worker] regionserver.RSZookeeperUpdater(141): Aborting open of region 13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:13,800 DEBUG [RegionServer:0.worker] regionserver.RSZookeeperUpdater(157): Updating ZNode /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464 with [RS2ZK_REGION_CLOSED] expected version = 0
org.apache.zookeeper.KeeperException$BadVersionException: KeeperErrorCode = BadVersion for /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
2010-06-23 15:42:13,802 ERROR [RegionServer:0.worker] regionserver.HRegionServer(1473): Failed to abort open region test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464.
java.io.IOException: org.apache.zookeeper.KeeperException$BadVersionException: KeeperErrorCode = BadVersion for /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464
Caused by: org.apache.zookeeper.KeeperException$BadVersionException: KeeperErrorCode = BadVersion for /1/UNASSIGNED/13bef4950ac6827ac32d87682b8b2464

Basically:

1. A region server was opening the region
2. It was expired just before reporting that the region is opened, leaving the znode in the state RS2ZK_REGION_OPENING
3. The region gets reassigned, it sees that state, doesn't change it, but still outputs in the end "Created UNASSIGNED zNode test,lll,1277332918248.13bef4950ac6827ac32d87682b8b2464. in state M2ZK_REGION_OFFLINE"
4. When the region server opens the region, it sees that the state is wrong and aborts opening the region

I think that the way to fix it is to change the state to what it should be.