JobQueueJobInProgressListener.jobUpdated() might not work as expected
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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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