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From "Steve Loughran (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4016) TaskTrackers never (re)connect back to the JobTracker if the JobTracker node/machine is changed
Date Mon, 10 Nov 2008 16:17:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4016?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12646287#action_12646287

Steve Loughran commented on HADOOP-4016:

-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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