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https://issues.apache.org/jira/browse/HADOOP-1111?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12480560
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Tom White commented on HADOOP-1111:
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Alejandro - I don't think you're missing anything. The Hadoop retry framework
is currently only appropriate for synchronous retries, whereas this patch uses
asynchronous retries to avoid tying up the JobTracker.
Stepping back a moment, though, I wonder why we need retries for job
notification - could we start out simple and add them later? If not, could we
look at the retry mechanisms that HttpClient provides
(http://jakarta.apache.org/commons/httpclient/exception-handling.html). Or
perhaps synchronous retries (using the Hadoop retry framework) from a
LinkedBlockingQueue (as David suggests) would do.
Why is there a special case for local runner notification? Could it not use the
same mechanism as the more general case? (Also, I think the code in
localRunnerNotification may go into an infinite loop if exceptions keep
occurring, since I can't see where the number of retries is decremented.)
> 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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