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https://issues.apache.org/jira/browse/MAPREDUCE-5576?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Zhijie Shen updated MAPREDUCE-5576:
-----------------------------------

    Summary: MR AM unregistration should not be failed due to 
UnknownHostException on getting history url  (was: MR AM unregistration should 
be failed due to UnknownHostException on getting history url)

> MR AM unregistration should not be failed due to UnknownHostException on 
> getting history url
> --------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-5576
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-5576
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>            Reporter: Zhijie Shen
>            Assignee: Zhijie Shen
>
> Before RMCommunicator sends the request to RM to finish the application, it 
> will try to get the JHS url, which may throw UnknownHostException. The 
> current code path will skip sending the request to RM when the exception is 
> raised, which sounds not a reasonable behavior, because RM's unregistering an 
> AM will not affected by the tracking URL. The URL can be empty or null. 
> AFAIK, the impact of null URL will be that the URL to redirect users from RM 
> web page to JHS will be unavailable, and the job report will not show the URL 
> as well. However, is it much much better than failing an application because 
> of UnknownHostException here? Anyway, users can go to JHS directly to find 
> the application history info.
> Therefore, the reasonable code path here should be catching 
> UnknownHostException and set historyUrl = null



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