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Hadoop, mail # user - Tasktracker appearing from "nowhere"

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Re: Tasktracker appearing from "nowhere"
Hemanth Yamijala 2010-05-28, 09:51

> I'm getting the following errors:
> WARN org.apache.hadoop.mapred.JobTracker: Serious problem, cannot find record of 'previous' heartbeat for 'tracker_m351.ra.wink.com:localhost/';
> reinitializing the tasktracker
> INFO org.apache.hadoop.mapred.JobTracker: Adding task 'attempt_201005271529_0004_r_000042_1' to tip task_201005271529_0004_r_000042, for tracker
> 'tracker_m351.ra.wink.com:localhost/'
> INFO org.apache.hadoop.mapred.JobTracker: Removed completed task 'attempt_201005271529_0004_m_000112_0' from 'tracker_m351.ra.wink.com:localhost/'
> despite not having m351 in any of the config files except racks.txt.
> If I take it out of there I can't start any jobs at all.
> Question is - what would make a machine be contacted as a tasktracker when it is not in the slave or *.xml files?

If m351 has Hadoop and a mapred-site.xml or hadoop-site.xml pointing
to the right JobTracker, it would register itself as a TaskTracker
when Hadoop starts on it. The slave file is used primarily to start
the daemons from a central place and is not a way to specify which
nodes must join the Hadoop cluster.