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From Gautama Kowshik <gautamkows...@gmail.com>
Subject Re: Reducer getting stuck after 66% processing
Date Fri, 07 Jan 2011 05:12:50 GMT
Reducers are supposed to stream out data. Do not wait for the last  
value to arrive in the reduce to put it out in the collector. Call  
output.collect on each value.

Sent from my iPhone

On Jan 6, 2011, at 1:26 AM, Dhaval Makawana<dhaval.makawana@gmail.com>  
wrote:

> Hi,
>
>
>
> I have 1 GB of input data with 10954103 records going to 7 reducer  
> tasks.
> The cluster is set up is such that each reducer gets 1 GB of RAM and  
> 256 MB
> out of it is reserved for sorting.  The reducer simply sums up one  
> field of
> values and outputs all the values along with the sum value. The  
> problem is
> all reducers are getting stuck after around 66% of processing. Tail  
> of task
> tracker log reads as below.
>
>
>
> 2011-01-06 08:39:31,309 INFO org.apache.hadoop.mapred.ReduceTask:
> Interleaved on-disk merge complete: 0 files left.
>
> 2011-01-06 08:39:31,309 INFO org.apache.hadoop.mapred.ReduceTask: In- 
> memory
> merge complete: 2 files left.
>
> 2011-01-06 08:39:31,333 INFO org.apache.hadoop.mapred.Merger:  
> Merging 2
> sorted segments
>
> 2011-01-06 08:39:31,334 INFO org.apache.hadoop.mapred.Merger: Down  
> to the
> last merge-pass, with 1 segments left of total size: 25352535 bytes
>
> 2011-01-06 08:39:31,343 INFO  
> org.apache.hadoop.io.compress.CodecPool: Got
> brand-new compressor
>
> 2011-01-06 08:39:31,704 INFO org.apache.hadoop.mapred.ReduceTask:  
> Merged 2
> segments, 25352537 bytes to disk to satisfy reduce memory limit
>
> 2011-01-06 08:39:31,704 INFO org.apache.hadoop.mapred.ReduceTask:  
> Merging 1
> files, 2947959 bytes from disk
>
> 2011-01-06 08:39:31,705 INFO org.apache.hadoop.mapred.ReduceTask:  
> Merging 0
> segments, 0 bytes from memory into reduce
>
> 2011-01-06 08:39:31,705 INFO org.apache.hadoop.mapred.Merger:  
> Merging 1
> sorted segments
>
> 2011-01-06 08:39:31,709 INFO org.apache.hadoop.mapred.Merger: Down  
> to the
> last merge-pass, with 1 segments left of total size: 2947955 bytes
>
>
> Please help solving the problem.
>
>
> Regards,
>
> Dhaval

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