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https://issues.apache.org/jira/browse/HADOOP-4016?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12646287#action_12646287
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Steve Loughran commented on HADOOP-4016:
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-to get DNS changes picked up then, we need two things
1. JVM settings to limit DNS caching in the TaskTracker to something everyone
is happy with.
2. renew hostname lookup after failures
I'd still push for a complete lookup of the mapred.job.tracker string. It is
easier to write tests for this, and on systems that have used alternate
configuration back ends (I know, still on my todo list), they get to pick these
values up from the CM infrastructure. That would let people roll out new
JobTracker locations without playing with DNS, just edit the tracker URL to
point to the new host
> TaskTrackers never (re)connect back to the JobTracker if the JobTracker
> node/machine is changed
> -----------------------------------------------------------------------------------------------
>
> Key: HADOOP-4016
> URL: https://issues.apache.org/jira/browse/HADOOP-4016
> Project: Hadoop Core
> Issue Type: Bug
> Components: mapred
> Reporter: Amar Kamat
>
> I tried the following
> 1) Started a hadoop cluster.
> 2) Killed the JT
> 3) Selected a new node for starting JT.
> 4) Changed the entry on the tasktracker to reflect the new (old) hostname to
> (new) ip mapping. Checked if the tracker node correctly resolves the hostname
> to the new ip.
> 5) Start the JT on the new node
> The tasktracker fails to connect to the new jobtracker. It seems that the
> hostname resolution remains stale and is never updated.
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