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From "Amareshwari Sriramadasu (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5374) NPE in JobTracker.getTasksToSave() method
Date Tue, 17 Mar 2009 06:44:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5374?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12682571#action_12682571

Amareshwari Sriramadasu commented on HADOOP-5374:

There are three threads in JobTracker updating the TaskStatuses : ExpireTrackers, ExpireLaunchingTasks
and heartbeat threads.
1. If heartbeat runs first, there is no issue with ExpireTrackers and  ExpireLaunchingTasks
threads, since the entry will removed from them.
2. If ExpireTrackers runs first, there is no issue with heartbeat(The tracker will be re-inited)
and ExpireLaunchingTasks(he task-entry will removed from the thread).
3. If ExpireLaunchingTasks runs first,
    a) If ExpireTrackers runs second, the task attempt will be Killed again. The task will
have FAILED, followed by KILLED update.
    b) If heartbeat runs second, If the TaskStatus is UNASSIGNED, RUNNING, COMMIT_PENDING
or SUCCEDED, the task will be added to taskToKill map and the update is ignored. So, the tasks
will be sent KillTaskAction(fixed by HADOOP-5280). If the state is COMMIT_PENDING, it throws
NPE as described in this jira.
I propose this issue can fix both 3(a) and 3(b).

> NPE in JobTracker.getTasksToSave() method
> -----------------------------------------
>                 Key: HADOOP-5374
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5374
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.20.0
>            Reporter: Vinod K V
>            Assignee: Amareshwari Sriramadasu
>         Attachments: patch-5374-1.txt

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