[jira] [Created] (MAPREDUCE-5576) MR AM unregistration should be failed due to UnknownHostException on getting history url

["Zhijie Shen (JIRA)" <ji...@apache.org>]

Zhijie Shen created MAPREDUCE-5576:
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             Summary: MR AM unregistration should 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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