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Date: Fri, 10 Oct 2008 09:17:44 -0700 (PDT)
From: "Vivek Ratan (JIRA)" <jira@apache.org>
To: core-dev@hadoop.apache.org
Subject: [jira] Commented: (HADOOP-4053) Schedulers need to know when a job
 has completed
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    [ https://issues.apache.org/jira/browse/HADOOP-4053?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12638582#action_12638582 ] 

Vivek Ratan commented on HADOOP-4053:
-------------------------------------

bq. Do we need JobStatusChangeEvent(JobInProgress jip, EventType eventType, JobStatus status) ?

I also feel we don't need this. Whether the old state or new state matters or not is a decision left to the code that consumes the event change. The creator of this event shouldn't make that decision. I think we should ensure that there is always an old state and new state (so 'null' should not be used). _finalizeJob()_ should also provide an old and new state. If the Capacity Scheduler chooses to ignore the old state, so be it, but some other listener may not. So I'm basically recommending that: 
* have only one constructor in JobStatusChangeEvent, which accepts both an old state and new state. 
* Neither of these states should be null. 
* Can these two states be the same object? I don't see why not. I can't think of a situation where they would be, but forcing the restriction that the states be different seems unnecessary. 

Seems OK to have _JonInProgress.initTasks()_ do the event notification. _initTasks()_ changes the state of a job, so the event notification should always happen. 

> Schedulers need to know when a job has completed
> ------------------------------------------------
>
>                 Key: HADOOP-4053
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4053
>             Project: Hadoop Core
>          Issue Type: Improvement
>    Affects Versions: 0.19.0
>            Reporter: Vivek Ratan
>            Assignee: Amar Kamat
>            Priority: Blocker
>         Attachments: HADOOP-4053-v1.patch, HADOOP-4053-v2.patch, HADOOP-4053-v3.1.patch, HADOOP-4053-v3.2.patch, HADOOP-4053-v4.1.patch, HADOOP-4053-v4.patch
>
>
> The JobInProgressListener interface is used by the framework to notify Schedulers of when jobs are added, removed, or updated. Right now, there is no way for the Scheduler to know that a job has completed. jobRemoved() is called when a job is retired, which can happen many hours after a job is actually completed. jobUpdated() is called when a job's priority is changed. We need to notify a listener when a job has completed (either successfully, or has failed or been killed). 

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