reducers stuck at shuffling
----------------------------
Key: HADOOP-3155
URL: https://issues.apache.org/jira/browse/HADOOP-3155
Project: Hadoop Core
Issue Type: Bug
Reporter: Runping Qi
This happened with hadoop-0.16.2:
In relatively small job (a few hundreds of mappers and reducers), reducers were
stuck at shuffling.
I saw the lines like the following repeated hundreds of thousands of times over
a few hours:
2008-04-02 17:17:44,640 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:17:44,641 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:17:44,641 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:17:44,641 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:17:46,643 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:17:46,643 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:17:46,643 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:17:46,643 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:17:48,645 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:17:48,645 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:17:48,645 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:17:48,645 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:17:50,647 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:17:50,647 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:17:50,647 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:17:50,647 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:17:52,649 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:17:52,650 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:17:52,650 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:17:52,650 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:17:54,651 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:17:54,652 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:17:54,652 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:17:54,652 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:17:56,654 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:17:56,654 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:17:56,654 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:17:56,654 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:17:58,656 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:17:58,656 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:17:58,656 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:17:58,656 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:00,658 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:00,658 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:00,658 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:00,658 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:02,660 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:02,661 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:02,661 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:02,661 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:04,662 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:04,663 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:04,663 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:04,663 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:06,664 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:06,665 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:06,665 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:06,665 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:08,667 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:08,667 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:08,667 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:08,667 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:10,669 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:10,669 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:10,669 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:10,669 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:12,671 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:12,671 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:12,671 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:12,671 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:14,673 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:14,674 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:14,674 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:14,674 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:16,675 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:16,676 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:16,676 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:16,676 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:18,678 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:18,678 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:18,678 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:18,678 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:20,680 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:20,680 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:20,680 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
2008-04-02 17:18:20,680 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Scheduled 0 of 0 known outputs (0 slow hosts
and 0 dup hosts)
2008-04-02 17:18:22,682 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Need 2 map output(s)
2008-04-02 17:18:22,682 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0: Got 0 new map-outputs & 0 obsolete
map-outputs from tasktracker and 0 map-outputs from previous failures
2008-04-02 17:18:22,682 INFO org.apache.hadoop.mapred.ReduceTask:
task_200804021200_0337_r_000008_0 Got 0 known map output location(s);
scheduling...
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