[HBASE-7259] Deadlock in HBaseClient when KeeperException occured

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 0.94.0, 0.94.1, 0.94.2
• Fix Version/s: 0.94.4
• Component/s: Zookeeper
• Assignee: Unassigned
• Reporter: Wei Li
• Created: 03/Dec/12 07:38
• Updated: 13/Jan/13 06:28
• Resolved: 19/Dec/12 23:49

Description

HBaseClient was running after a period of time, all of get operation became too slow.

From the client logs I could see the following:

1. Unable to get data of znode /hbase/root-region-server

java.lang.InterruptedException
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:485)
        at org.apache.zookeeper.ClientCnxn.submitRequest(ClientCnxn.java:1253)
        at org.apache.zookeeper.ZooKeeper.getData(ZooKeeper.java:1129)
        at org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper.getData(RecoverableZooKeeper.java:264)
        at org.apache.hadoop.hbase.zookeeper.ZKUtil.getDataInternal(ZKUtil.java:522)
        at org.apache.hadoop.hbase.zookeeper.ZKUtil.getDataAndWatch(ZKUtil.java:498)
        at org.apache.hadoop.hbase.zookeeper.ZooKeeperNodeTracker.getData(ZooKeeperNodeTracker.java:156)
        at org.apache.hadoop.hbase.zookeeper.RootRegionTracker.getRootRegionLocation(RootRegionTracker.java:62)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:821)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:801)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegionInMeta(HConnectionManager.java:933)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:832)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:801)
        at org.apache.hadoop.hbase.client.HTable.finishSetup(HTable.java:234)
        at org.apache.hadoop.hbase.client.HTable.<init>(HTable.java:174)
        at org.apache.hadoop.hbase.client.MetaScanner.metaScan(MetaScanner.java:150)
        at org.apache.hadoop.hbase.client.MetaScanner.access$000(MetaScanner.java:48)
        at org.apache.hadoop.hbase.client.MetaScanner$1.connect(MetaScanner.java:126)
        at org.apache.hadoop.hbase.client.MetaScanner$1.connect(MetaScanner.java:123)
        at org.apache.hadoop.hbase.client.HConnectionManager.execute(HConnectionManager.java:359)
        at org.apache.hadoop.hbase.client.MetaScanner.metaScan(MetaScanner.java:123)
        at org.apache.hadoop.hbase.client.MetaScanner.metaScan(MetaScanner.java:99)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.prefetchRegionCache(HConnectionManager.java:894)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegionInMeta(HConnectionManager.java:948)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:836)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:801)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getRegionLocation(HConnectionManager.java:725)
        at org.apache.hadoop.hbase.client.ServerCallable.connect(ServerCallable.java:82)
        at org.apache.hadoop.hbase.client.ServerCallable.withRetries(ServerCallable.java:162)
        at org.apache.hadoop.hbase.client.HTable.get(HTable.java:685)
        at org.apache.hadoop.hbase.client.HTablePool$PooledHTable.get(HTablePool.java:366)

2. Catalina.out found one Java-level deadlock:

=============================

"catalina-exec-800":
  waiting to lock monitor 0x000000005f1f6530 (object 0x0000000731902200, a java.lang.Object),
  which is held by "catalina-exec-710"
"catalina-exec-710":
  waiting to lock monitor 0x00002aaab9a05bd0 (object 0x00000007321f8708, a org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation),
  which is held by "catalina-exec-29-EventThread"
"catalina-exec-29-EventThread":
  waiting to lock monitor 0x000000005f9f0af0 (object 0x0000000732a9c7e0, a org.apache.hadoop.hbase.zookeeper.RootRegionTracker),
  which is held by "catalina-exec-710"
Java stack information for the threads listed above:

===================================================

"catalina-exec-800":
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegionInMeta(HConnectionManager.java:943)
        - waiting to lock <0x0000000731902200> (a java.lang.Object)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:836)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.relocateRegion(HConnectionManager.java:807)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getRegionLocation(HConnectionManager.java:725)
        at org.apache.hadoop.hbase.client.ServerCallable.connect(ServerCallable.java:82)
        at org.apache.hadoop.hbase.client.ServerCallable.withRetries(ServerCallable.java:162)
        at org.apache.hadoop.hbase.client.HTable.get(HTable.java:685)
        at org.apache.hadoop.hbase.client.HTablePool$PooledHTable.get(HTablePool.java:366)
"catalina-exec-710":
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.resetZooKeeperTrackers(HConnectionManager.java:599)
        - waiting to lock <0x00000007321f8708> (a org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.abort(HConnectionManager.java:1660)
        at org.apache.hadoop.hbase.zookeeper.ZooKeeperNodeTracker.getData(ZooKeeperNodeTracker.java:158)
        - locked <0x0000000732a9c7e0> (a org.apache.hadoop.hbase.zookeeper.RootRegionTracker)
        at org.apache.hadoop.hbase.zookeeper.RootRegionTracker.getRootRegionLocation(RootRegionTracker.java:62)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:821)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:801)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegionInMeta(HConnectionManager.java:933)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:832)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:801)
        at org.apache.hadoop.hbase.client.HTable.finishSetup(HTable.java:234)
        at org.apache.hadoop.hbase.client.HTable.<init>(HTable.java:174)
        at org.apache.hadoop.hbase.client.MetaScanner.metaScan(MetaScanner.java:150)
        at org.apache.hadoop.hbase.client.MetaScanner.access$000(MetaScanner.java:48)
        at org.apache.hadoop.hbase.client.MetaScanner$1.connect(MetaScanner.java:126)
        at org.apache.hadoop.hbase.client.MetaScanner$1.connect(MetaScanner.java:123)
        at org.apache.hadoop.hbase.client.HConnectionManager.execute(HConnectionManager.java:359)
        at org.apache.hadoop.hbase.client.MetaScanner.metaScan(MetaScanner.java:123)
        at org.apache.hadoop.hbase.client.MetaScanner.metaScan(MetaScanner.java:99)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.prefetchRegionCache(HConnectionManager.java:894)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegionInMeta(HConnectionManager.java:948)
        - locked <0x0000000731902200> (a java.lang.Object)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.locateRegion(HConnectionManager.java:836)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.relocateRegion(HConnectionManager.java:807)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.getRegionLocation(HConnectionManager.java:725)
        at org.apache.hadoop.hbase.client.ServerCallable.connect(ServerCallable.java:82)
        at org.apache.hadoop.hbase.client.ServerCallable.withRetries(ServerCallable.java:162)
        at org.apache.hadoop.hbase.client.HTable.get(HTable.java:685)
        at org.apache.hadoop.hbase.client.HTablePool$PooledHTable.get(HTablePool.java:366)
"catalina-exec-29-EventThread":
        at org.apache.hadoop.hbase.zookeeper.ZooKeeperNodeTracker.stop(ZooKeeperNodeTracker.java:98)
        - waiting to lock <0x0000000732a9c7e0> (a org.apache.hadoop.hbase.zookeeper.RootRegionTracker)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.resetZooKeeperTrackers(HConnectionManager.java:604)
        - locked <0x00000007321f8708> (a org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation)
        at org.apache.hadoop.hbase.client.HConnectionManager$HConnectionImplementation.abort(HConnectionManager.java:1660)
        at org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.connectionEvent(ZooKeeperWatcher.java:374)
        at org.apache.hadoop.hbase.zookeeper.ZooKeeperWatcher.process(ZooKeeperWatcher.java:271)
        at org.apache.zookeeper.ClientCnxn$EventThread.processEvent(ClientCnxn.java:521)
        at org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:497)
Found 1 deadlock.

From the source code , the reason for this problem is doing ZooKeeperNodeTracker.getData that lead to KeeperException. And try to resetZookeeperTracker. At the same time, ClientCnxn.EventThread also do resetZookeeperTracker ,too. Because of getData have already held the lock of ZooKeeperNodeTracke , that lead to the order of the lock two threads to obtain does not accord. So deadlock happened.

In order to avoid the problem, we can add if reseting condition in abortable.abort()
See the patch.