NPE in SafeModeMonitor

• Key: HADOOP-3489
• Type: Bug
• Status: Closed
• Resolution: Fixed
• Priority: Major
• Assignee: Lohit Vijayarenu
• Reporter: Konstantin Shvachko
• Affects Version/s: 0.18.0
• Fix Version/s: 0.18.0

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.

Comments

[Lohit Vijayarenu]

How about just checking if it is not null before trying canLeave?

[Konstantin Shvachko]

+1

[Lohit Vijayarenu]

[exec] +1 @author. The patch does not contain any @author tags.
[exec]
[exec] -1 tests included. The patch doesn't appear to include any new or modified tests.
[exec] Please justify why no tests are needed for this patch.
[exec]
[exec] +1 javadoc. The javadoc tool did not generate any warning messages.
[exec]
[exec] +1 javac. The applied patch does not increase the total number of javac compiler warnings.
[exec]
[exec] +1 findbugs. The patch does not introduce any new Findbugs warnings.
[exec]

[Konstantin Shvachko]

I just committed this. Thank you Lohit.