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From "Amar Kamat (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4068) JobTracker might wrongly log a tip as failed
Date Fri, 05 Sep 2008 03:15:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4068?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12628537#action_12628537
] 

Amar Kamat commented on HADOOP-4068:
------------------------------------

+1

> JobTracker might wrongly log a tip as failed
> --------------------------------------------
>
>                 Key: HADOOP-4068
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4068
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>            Reporter: Amar Kamat
>
> Consider the following case
> 1) attempt _attempt_1_0_ from tip _tip_1_ that ran on tracker _tracker_1_ failed
> 2) jobtracker will mark _attempt_1_0_ for removal under _tracker_1_. Marking basically
means removal of the mapping _tracker_1_->_attempt_1_0_
> 3) Marked attempts are removed only on next heartbeat from _tracker__1 or when _tracker_1_
is lost.
> 4) Consider a case where _tracker_1_ goes down.
> 5) In the meanwhile attempt _attempt_1_1_ succeeds on _tracker_2_ and the jobtracker
marks the tip _tip_1_ as complete
> 6) Now the expiry-tracker thread detect that _tracker_1_ is lost and fails all the attempt
under _tracker_1_. 
> 7) Here the jobtracker will kill _attempt_1_0_ *again* and log tip _tip_1_ as failed
in the history although tip _tip_1_ is really complete/succeeded.
> The events in the history file would be something like
> {noformat}
> tip_1 start
> ---------
> attempt_1_0 start
> attempt_1_0 failed
> ---------
> attempt_1_1 start
> attempt_1_1 finished
> tip_1 finished
> ---------
> tip_1 failed
> {noformat}
> Note that this true even for tasks that expire. Tasks that are scheduled and never come
back are killed by the {{ExpireLaunchingTasks}} thread. It will also call {{JobInProgress.failedTask()}}
which will fail the attempt and log the TIP as failed.

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