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From "Vivek Ratan (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4149) JobQueueJobInProgressListener.jobUpdated() might not work as expected
Date Mon, 06 Oct 2008 22:03:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12637266#action_12637266
] 

Vivek Ratan commented on HADOOP-4149:
-------------------------------------

HADOOP-3445 faces the same issue. JobQueuesManager.QueueInfo implements its own removal method
that deletes an object from a TreeSet based on referential equality, rather than value equality
that the TreeSet uses. 

> JobQueueJobInProgressListener.jobUpdated() might not work as expected
> ---------------------------------------------------------------------
>
>                 Key: HADOOP-4149
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4149
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: mapred
>    Affects Versions: 0.19.0
>            Reporter: Amar Kamat
>            Assignee: Amar Kamat
>            Priority: Blocker
>             Fix For: 0.19.0
>
>
> {{JobQueueJobInProgressListener}} uses a {{TreeSet}} to store the sorted collection of
{{JobInProgress}} objects. The comparator used to sort the JIPs follow the following order
> - priority (>=)
> - start time (<=)
> - job id [jt-identifier, job-index] (<=)
> If any JIP object is changed w.r.t priority or start-time, then the TreeSet will be inconsistent.
Hence doing  a delete might not work. Consider the following
> 1) jobs are submitted in the following order 
> ||number||jobid||priority||
> |1|j1|NORMAL|
> |2|j2|LOW|
> |3|j3|NORMAL|
> 2) The sorted collection will be in the order : {{j1,j3,j2}}
> 3) If job3's priority is changed to LOW then the collection wont change but delete will
bail out on j1 itself as the comparator will return a -ve number. TreeSet uses the comparator
both for sorting and deleting. If  i indicates the index in the collection and obj represents
the object under consideration, then looks like TreeSet.remove(obj) follows something like
 :
> - continue to search if the compare(i, obj) is -ve
> - bail out if the compare(i, obj) is +ve
> - delete the obj of compare(i,obj) == 0

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