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From "Fuad Efendi" <f...@efendi.ca>
Subject RE: Copyphase dies on timeout
Date Wed, 09 Dec 2009 18:39:14 GMT
I had similar issues before; Reduce can do some 'additional' processing and have dependency
on external services.

For instance, in my case it sends documents to SOLR (Lucene based). So that I have dependency
on Lucene in a reducer. And, Lucene sometimes needs 30-50 minutes to perform index merge.
If your timeout settings are not enough, job will be killed. You may also execute reporter.keepAlive()
each 60 seconds (in a separate thread spawned by your reducer).

See at <name>mapred.task.timeout</name>, and use reporter.progress(), keepAlive(),
etc.


Fuad Efendi
+1 416-993-2060
http://www.tokenizer.ca
Data Mining, Vertical Search


> -----Original Message-----
> From: Simon Willnauer [mailto:simon.willnauer@googlemail.com]
> Sent: December-09-09 1:31 PM
> To: mapreduce-user@hadoop.apache.org
> Subject: Copyphase dies on timeout
> 
> Hi folks,
> 
> I do have a questions regarding a map-reduce job who gets killed
> during the copy phase due to a timeout. I don't really understand the
> output completely so I first look for some help to understand what is
> going on.
> There are about 50 mapper running where each mapper succeeds. the job
> is configured with a single reduces (I assume this could be closely
> related to that?!)
> So this is the output:
> 
> 2009-12-09 15:01:45,103 INFO org.apache.hadoop.mapred.Merger: Merging
> 5 sorted segments
> 2009-12-09 15:01:45,103 INFO org.apache.hadoop.mapred.Merger: Down to
> the last merge-pass, with 5 segments left of total size: 216092233
> bytes
> 2009-12-09 15:01:50,727 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Merge of the 5 files in-memory
> complete. Local file is
> /data/hadoop-
> data/mapred/local/taskTracker/jobcache/job_200912081402_0042/attempt_20091
> 2081402_0042_r_000000_0/output/map_275.out
> of size 216092229
> 2009-12-09 15:01:50,728 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Thread waiting: Thread for
> merging on-disk files
> 2009-12-09 15:01:58,109 INFO org.apache.hadoop.mapred.ReduceTask: Read
> 53281055 bytes from map-output for
> attempt_200912081402_0042_m_000253_0
> 2009-12-09 15:01:58,148 INFO org.apache.hadoop.mapred.ReduceTask: Rec
> #1 from attempt_200912081402_0042_m_000253_0 -> (71, 103) from
> hadoop32
> 2009-12-09 15:01:58,273 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Need another 44 map output(s)
> where 3 is already in progress
> 2009-12-09 15:01:58,273 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Scheduled 0 outputs (0 slow hosts
> and41 dup hosts)
> 2009-12-09 15:02:40,174 INFO org.apache.hadoop.mapred.ReduceTask: Read
> 81297732 bytes from map-output for
> attempt_200912081402_0042_m_000112_0
> 2009-12-09 15:02:40,175 INFO org.apache.hadoop.mapred.ReduceTask: Rec
> #1 from attempt_200912081402_0042_m_000112_0 -> (129, 153) from
> hadoop31
> 2009-12-09 15:02:40,175 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Scheduled 1 outputs (0 slow hosts
> and16 dup hosts)
> 2009-12-09 15:02:40,223 INFO org.apache.hadoop.mapred.ReduceTask:
> Shuffling 82364774 bytes (82364778 raw bytes) into RAM from
> attempt_200912081402_0042_m_000121_0
> 2009-12-09 15:02:45,044 INFO org.apache.hadoop.mapred.ReduceTask: Read
> 82722679 bytes from map-output for
> attempt_200912081402_0042_m_000196_0
> 2009-12-09 15:02:45,044 INFO org.apache.hadoop.mapred.ReduceTask: Rec
> #1 from attempt_200912081402_0042_m_000196_0 -> (114, 137) from
> hadoop21
> 2009-12-09 15:02:45,044 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Scheduled 1 outputs (0 slow hosts
> and32 dup hosts)
> 2009-12-09 15:02:45,143 INFO org.apache.hadoop.mapred.ReduceTask:
> Shuffling 82639206 bytes (82639210 raw bytes) into RAM from
> attempt_200912081402_0042_m_000195_0
> 2009-12-09 15:02:58,274 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Need another 42 map output(s)
> where 3 is already in progress
> 2009-12-09 15:02:58,274 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Scheduled 0 outputs (0 slow hosts
> and39 dup hosts)
> 2009-12-09 15:03:58,275 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Need another 42 map output(s)
> where 3 is already in progress
> 2009-12-09 15:03:58,275 INFO org.apache.hadoop.mapred.ReduceTask:
> attempt_200912081402_0042_r_000000_0 Scheduled 0 outputs (0 slow hosts
> and39 dup hosts)
> ......
> 
> Task attempt_200912081402_0042_r_000000_0 failed to report status for
> 902 seconds. Killing!
> 
> my first guess would be some IO problem but I don not have any
> indicator that those logs. If somebody can clarify or give me a hint
> would be great. Even if it is something like: use more reducers
> because of ... <-- this is the interesting part at the moment!
> btw: this is hadoop-0.20
> 
> simon



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