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From "John Zhuge (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-12125) Retrying UnknownHostException on a proxy does not actually retry hostname resolution
Date Thu, 15 Mar 2018 01:09:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12125?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16399707#comment-16399707
] 

John Zhuge commented on HADOOP-12125:
-------------------------------------

[~shahrs87] and [~jlowe], any progress? We hit the same issue when the non-HA NN went down
and AWS spun up another NN instance with a different IP address. Both Job History Server
and Spark History Server were stuck because NameNodeProxy held on to the old IP address.

> Retrying UnknownHostException on a proxy does not actually retry hostname resolution
> ------------------------------------------------------------------------------------
>
>                 Key: HADOOP-12125
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12125
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: ipc
>            Reporter: Jason Lowe
>            Assignee: Rushabh S Shah
>            Priority: Major
>
> When RetryInvocationHandler attempts to retry an UnknownHostException the hostname fails
to be resolved again.  The InetSocketAddress in the ConnectionId has cached the fact that
the hostname is unresolvable, and when the proxy tries to setup a new Connection object with
that ConnectionId it checks if the (cached) resolution result is unresolved and immediately
throws.
> The end result is we sleep and retry for no benefit.  The hostname resolution is never
attempted again.



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