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https://issues.apache.org/jira/browse/HADOOP-4149?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12635954#action_12635954
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Hemanth Yamijala commented on HADOOP-4149:
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To see an impact of this bug, I submitted three jobs (using the default
scheduler), and changed the priority of one of them. In the
jobqueue_details.jsp page, I saw that the job which changed priority is listed
twice ! It is the same object being referred to, but as Amar pointed out, since
it is not deleted, it shows up twice. I think schedulers could be affected by
this, for e.g. if they do not check for a job's run state, they may think the
job in the run list or queued list is still to be considered and work on them.
It seems like a blocker based on this. Setting it as such. If someone feels
not, please comment here.
> 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
> Reporter: Amar Kamat
>
> {{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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