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From "Runping Qi" <runp...@yahoo-inc.com>
Subject RE: reducers hanging problem
Date Mon, 30 Jun 2008 16:38:28 GMT

Looks like the reducer stuck at shuffling phase.
What is the progression percentage do you see for the reducer from web
GUI?

It is known that 0.17 does not handle shuffling well.

Runping


> -----Original Message-----
> From: Andreas Kostyrka [mailto:andreas@kostyrka.org]
> Sent: Monday, June 30, 2008 8:30 AM
> To: core-user@hadoop.apache.org
> Subject: reducers hanging problem
> 
> Hi!
> 
> I'm running streaming tasks on hadoop 0.17.0, and wondered, if anyone
has
> an
> approach to debugging the following situation:
> 
> -) map have all finished (100% in http display),
> -) some reducers are hanging, with the messages below.
> 
> Notice, that the task had 100 map tasks at allo, so 58 seems like an
> extraordinary high number of missing parts, long after map has
officially
> finished. Plus it seems to be deterministic, it always stop at 3
reduce
> parts
> not finishing, although I haven't yet checked if they are always the
same
> errors or not.
> 
> > 2008-06-30 15:25:41,953 INFO org.apache.hadoop.mapred.ReduceTask:
> > task_200806300847_0002_r_000014_0 Need 58 map output(s) 2008-06-30
> > 15:25:41,953 INFO org.apache.hadoop.mapred.ReduceTask:
> > task_200806300847_0002_r_000014_0: Got 0 new map-outputs & 0
obsolete
> > map-outputs from tasktracker and 0 map-outputs from previous
failures
> > 2008-06-30 15:25:41,954 INFO org.apache.hadoop.mapred.ReduceTask:
> > task_200806300847_0002_r_000014_0 Got 0 known map output
location(s);
> > scheduling... 2008-06-30 15:25:41,954 INFO
> > org.apache.hadoop.mapred.ReduceTask:
task_200806300847_0002_r_000014_0
> > Scheduled 0 of 0 known outputs (0 slow hosts and 0 dup hosts)
2008-06-30
> > 15:25:46,770 INFO org.apache.hadoop.streaming.PipeMapRed:
MRErrorThread
> > done 2008-06-30 15:25:46,963 INFO
org.apache.hadoop.mapred.ReduceTask:
> > task_200806300847_0002_r_000014_0 Need 58 map output(s) 2008-06-30
> > 15:25:46,963 INFO org.apache.hadoop.mapred.ReduceTask:
> > task_200806300847_0002_r_000014_0: Got 0 new map-outputs & 0
obsolete
> > map-outputs from tasktracker and 0 map-outputs from previous
failures
> > 2008-06-30 15:25:46,964 INFO org.apache.hadoop.mapred.ReduceTask:
> > task_200806300847_0002_r_000014_0 Got 0 known map output
location(s);
> > scheduling... 2008-06-30 15:25:46,964 INFO
> > org.apache.hadoop.mapred.ReduceTask:
task_200806300847_0002_r_000014_0
> > Scheduled 0 of 0 known outputs (0 slow hosts and 0 dup hosts)
> 
> TIA,
> 
> Andreas

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