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From Steve Loughran <ste...@apache.org>
Subject Re: hadoop hangs on reduce
Date Mon, 21 Sep 2009 10:09:40 GMT
himanshu chandola wrote:
> Just as an update. I made a dummy map job so that the map outputs a unique key for every
input and hence the input to reduce is unique too. Still my reduce jobs hang at 76.02 % now
(I've added a few nodes into my cluster so I suspect what was earlier 96.49 is 76.02). So
this is definitely not a memory or io issue. 
> 
> Do I restart my task trackers ? (ive tried once but didnt help)
> 

I see reduce hangs when the TT's cant talk to each other, when they 
can't get data from the other TTs

check the value of mapred.task.tracker.report.address , that it is on an 
external address (not 127.0.0.1) and that the port in use is open on all 
the machines.

-steve


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