[HADOOP-3489] NPE in SafeModeMonitor

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.18.0
• Fix Version/s: 0.18.0
• Hadoop Flags: Reviewed
• Assignee: Lohit Vijaya Renu
• Reporter: Konstantin Shvachko
• Created: 04/Jun/08 22:32
• Updated: 08/Jul/09 16:43
• Resolved: 07/Jun/08 00:02

Description

If dfsadmin issues -safemode leave command when name-node is in the extended period of safe mode the SafeModeMonitor throws the following exception:

Exception in thread "org.apache.hadoop.dfs.FSNamesystem$SafeModeMonitor@dc86eb" java.lang.NullPointerException
	at org.apache.hadoop.dfs.FSNamesystem$SafeModeMonitor.run(FSNamesystem.java:3914)
	at java.lang.Thread.run(Thread.java:619)

The problem is that when SafeModeMonitor.run() wakes up it tries to check whether it canLeave() the safe mode, but the safe mode is off already,
and therefore the "safemode" field is null.