Null pointer exception in JobTracker when the task tracker is not yet resolved
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Key: HADOOP-3590
URL: https://issues.apache.org/jira/browse/HADOOP-3590
Project: Hadoop Core
Issue Type: Bug
Components: mapred
Reporter: Amar Kamat
Assignee: Amar Kamat
Priority: Blocker
Fix For: 0.18.0
2008-06-17 13:29:56,711 INFO org.apache.hadoop.mapred.JobTracker: Got heartbeat
from: xxx (initialContact: false acceptNewTasks: true) with responseId: 0
2008-06-17 13:29:56,711 INFO org.apache.hadoop.ipc.Server: IPC Server handler 7
on 123, call heartbeat([EMAIL PROTECTED], true, true, -1) from xxx error:
java.io.IOException: java.lang.NullPointerException
java.io.IOException: java.lang.NullPointerException
at
org.apache.hadoop.mapred.JobTracker.getParentNode(JobTracker.java:1327)
at
org.apache.hadoop.mapred.JobInProgress.findNewMapTask(JobInProgress.java:1142)
at
org.apache.hadoop.mapred.JobInProgress.obtainNewMapTask(JobInProgress.java:685)
at
org.apache.hadoop.mapred.JobTracker.getNewTaskForTaskTracker(JobTracker.java:1708)
at org.apache.hadoop.mapred.JobTracker.heartbeat(JobTracker.java:1431)
at sun.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.hadoop.ipc.RPC$Server.call(RPC.java:452)
at org.apache.hadoop.ipc.Server$Handler.run(Server.java:888)
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Looks like a corner case. This happens when the task tracker just joins the JT
and asks for a task to run. In a case where the task tracker is not yet
resolved, this can lead to null pointer exception. Remember that the task
trackers are added to separate queue and resolved by a separate thread i.e
there is no forced resolution for task trackers. There is no side effect of
this bug since the task tracker will try again and also the job runs to
completion.
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