[MAPREDUCE-754] NPE in expiry thread when a TT is lost

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.20.1
• Fix Version/s: 0.21.0
• Component/s: jobtracker
• Hadoop Flags: Reviewed

Release Note

Fixes the NPE in 'refreshNodes', ExpiryTracker thread and heartbeat. NPE occurred in the following cases
- a blacklisted tracker is either decommissioned or expires.
- a lost tracker gets blacklisted

• Assignee: Amar Kamat
• Reporter: Ramya Sunil
• Created: 13/Jul/09 12:03
• Updated: 24/Aug/10 21:14
• Resolved: 08/Dec/09 15:22

Description

NullPointerException is obtained in Tracker Expiry Thread. Below is the exception obtained in the JT logs

ERROR org.apache.hadoop.mapred.JobTracker: Tracker Expiry Thread got exception: java.lang.NullPointerException
        at org.apache.hadoop.mapred.JobTracker.updateTaskTrackerStatus(JobTracker.java:2971)
        at org.apache.hadoop.mapred.JobTracker.access$300(JobTracker.java:104)
        at org.apache.hadoop.mapred.JobTracker$ExpireTrackers.run(JobTracker.java:381)
        at java.lang.Thread.run(Thread.java:619)

The steps to reproduce this issue are:

• Blacklist a TT.
• Restart it.
• The above exception is obtained when the first instance of TT is marked as lost.

However the above exception does not break any functionality.

Issue Links

• is related to: MAPREDUCE-1188 NPE in decommissioning blacklisted nodes
• is related to: MAPREDUCE-746 When a task tracker is killed, there is a Null Pointer exception thrown.