[
https://issues.apache.org/jira/browse/HADOOP-3155?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12638475#action_12638475
]
Devaraj Das commented on HADOOP-3155:
-------------------------------------
bq. I deduced this scenario from looking at the tasktracker logs. So, my theory
is indeed validated. In out cluster, it typically ocurs during periods of high
load. The TaskTracker.close() already clears most data structures. In this
case, after the data strctures are cleared, the first instance of the fercher
thread re-populated the data structure and then exited. The second instance of
the fetcher thread continued using the data structure. Hence the duplicate
values. Does this make sense?
Dhruba, I don't quite see how this could happen (maybe I am missing something
and I hope so *smile*). Even if you have two threads live at some point, both
of them would be sharing the same object (FetchStatus) and hence should be
seeing the same fromEventId, no?
So if the first thread repopulated the datastructure, the second thread should
be seeing the same fromEventId object (and hence would be seeing the same
value), no? Also, note that two concurrent fetching of map completion events
for the same job cannot happen since the fetch is synchronized on the
fromEventId object.
I do agree that we should not have two concurrent fetcher threads live
simultaneously.
> 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
> Assignee: dhruba borthakur
> Fix For: 0.19.0
>
> Attachments: events-job_200807311630_0007.txt, fetcherThread.patch,
> fetcherThread.patch, fetcherThread.patch, hadoop-3155-logs.tar.gz,
> jobevents_1007.txt, patch-3155-debug-0.16.txt, patch-3155-debug-0.17.txt,
> task_200807311630_0007_r_000006_0.syslog.gz
>
>
> 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...
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
