slow reduce copies - map output locations not being fetched even when map
complete
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Key: HADOOP-2980
URL: https://issues.apache.org/jira/browse/HADOOP-2980
Project: Hadoop Core
Issue Type: Bug
Affects Versions: 0.15.3
Reporter: Joydeep Sen Sarma
maps are long finished. reduces are stuck looking for map locations. they make
progress - but slowly. it almost seems like they get new map locations every
minute or so:
2008-03-07 18:50:52,737 INFO org.apache.hadoop.mapred.ReduceTask:
task_200803041231_3586_r_000021_0 done copying
task_200803041231_3586_m_004620_0 output from hadoop082.sf2p.facebook.com..
2008-03-07 18:50:53,733 INFO org.apache.hadoop.mapred.ReduceTask:
task_200803041231_3586_r_000021_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-03-07 18:50:53,733 INFO org.apache.hadoop.mapred.ReduceTask:
task_200803041231_3586_r_000021_0 Got 0 known map output location(s);
scheduling...
...
2008-03-07 18:51:49,767 INFO org.apache.hadoop.mapred.ReduceTask:
task_200803041231_3586_r_000021_0 Got 50 known map output location(s);
scheduling...
2008-03-07 18:51:49,767 INFO org.apache.hadoop.mapred.ReduceTask:
task_200803041231_3586_r_000021_0 Scheduled 41 of 50 known outputs (0 slow
hosts and 9 dup hosts)
they get about 50 locations at a time and this 1 minute delay pattern is
surprisingly common ..
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