[jira] Commented: (HADOOP-3155) reducers stuck at shuffling

["Derek Wollenstein (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-3155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12612949#action_12612949 ] 

Derek Wollenstein commented on HADOOP-3155:
-------------------------------------------

I noticed something similar occuring to the original issue description (
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))
) repeated over and over again
It seems that this is triggered if different nodes are configured to use a different dfs name, including the following

on the TaskTracker and JobTracker instances

fs.default.name = "foo.example.com:50001"

on the DataNode instances

fs.default.name = "hdfs://foo.example.com:50001/"

This seems to cause the reducers to be unable to find the mapper output

> 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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