[HBASE-8536] Possible NullPointerException in ZKInterProcessLockBase#reapExpiredLocks

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.98.0, 0.95.1
• Hadoop Flags: Reviewed
• Assignee: Ted Yu
• Reporter: Ted Yu
• Created: 13/May/13 17:06
• Updated: 23/Sep/13 19:08
• Resolved: 14/May/13 18:15

Description

When I ran TestHBaseFsck, I sometimes saw:

testNoVersionFile(org.apache.hadoop.hbase.util.TestHBaseFsck)  Time elapsed: 0.003 sec  <<< ERROR!
java.io.IOException: java.lang.NullPointerException
        at org.apache.hadoop.hbase.master.TableLockManager$ZKTableLockManager.reapAllExpiredLocks(TableLockManager.java:433)
        at org.apache.hadoop.hbase.util.hbck.TableLockChecker.fixExpiredTableLocks(TableLockChecker.java:83)
        at org.apache.hadoop.hbase.util.HBaseFsck.checkAndFixTableLocks(HBaseFsck.java:2483)
        at org.apache.hadoop.hbase.util.HBaseFsck.onlineHbck(HBaseFsck.java:460)
        at org.apache.hadoop.hbase.util.hbck.HbckTestingUtil.doFsck(HbckTestingUtil.java:65)
        at org.apache.hadoop.hbase.util.hbck.HbckTestingUtil.doFsck(HbckTestingUtil.java:41)
        at org.apache.hadoop.hbase.util.hbck.HbckTestingUtil.doFsck(HbckTestingUtil.java:36)
        at org.apache.hadoop.hbase.util.TestHBaseFsck.testNoVersionFile(TestHBaseFsck.java:1086)
...
Caused by: java.lang.NullPointerException
        at org.apache.hadoop.hbase.zookeeper.lock.ZKInterProcessLockBase.reapExpiredLocks(ZKInterProcessLockBase.java:393)
        at org.apache.hadoop.hbase.master.TableLockManager$ZKTableLockManager.reapAllExpiredLocks(TableLockManager.java:427)
        ... 37 more

This was due to null being returned from ZKUtil.listChildrenNoWatch() at line 384:

      children = ZKUtil.listChildrenNoWatch(zkWatcher, parentLockNode);