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https://issues.apache.org/jira/browse/HADOOP-1111?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12480489
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David Bowen commented on HADOOP-1111:
-------------------------------------


I don't see the rationale for using a DelayQueue here, since no delay is 
required.  A LinkedBlockingQueue would seem more appropriate.

Is there some reason for using GET rather than POST?

Looks like the notification thread can only end with the error message that it 
is ending unexpectedly.  Right?

I think the running flag should be declared volatile.

Stylistically, I think a singleton class is generally preferable to a class 
with only static members.  But others may disagree.



> Job completion notification to a job configured URL
> ---------------------------------------------------
>
>                 Key: HADOOP-1111
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1111
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: mapred
>    Affects Versions: 0.12.0
>         Environment: all
>            Reporter: Alejandro Abdelnur
>         Attachments: patch-1111.txt, patch-1111.txt
>
>
> Currently clients have to poll the JobTracker to find if a job has completed 
> or not.
> When invoking Hadoop from other systems is desirable to have a notification 
> mechanism on job completion. 
> The notification approach simplifies the client waiting for completion and 
> removes load from the JobTracker as polling can be avoided. 
> Proposed solution:
> When the JobTracker processes the completion of a job (success and failure)  
> if the job configuration has a jobEnd.notificationUrl property it will make a 
> HTTP GET request to the specified URL.
> The jobEnd.notificationUrl property may include 2 variables in it '${jobId}' 
> and '${jobStatus}'. if they are present, they will be replaced with tehe job 
> ID and status of the job and the URL will be invoked.
> Two additional properties, 'jobEnd.retries' and 'jobEnd.retryInterval', will 
> indicate retry behavior.
> Not to delay the JobTracker processing while doing notifications, a 
> ConsumerProducer Queue will be used to queue up job notification upon 
> completion.
> A daemon thread will consume job notifications from the above Queue and will 
> make the URL invocation. 
> On notification failure, the job notification is  queue up again on the 
> notification queue.
> The queue will be a java.util.concurrent.DelayQueue. This will make job 
> notifications (on retries) to be avaiable on the consumer side only when the 
> retry time is up.
> The changes will be done in the JobTracker and in the LocalJobRunner.

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