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:[email protected]] > Sent: December-09-09 1:31 PM > To: [email protected] > 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
