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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