Hello Arun,
Thanks for the quick reply. I totally understand the CDH issue but figured I'd ask the broader community as well in case there was any upstream known issue as I've noticed some patches relating to "somewhat similar" issues. The jstack was currently on my radar but I hadn't even thought about tcpdump to catch weather the tasks were heartbeating or not so thanks for the tip, will make sure to check that out! We are also planning our release update to CDH 3u2 vs. 3u0 which will give us the updated hadoop 0.20.2+923.142 vs. our current 0.20.2+923.21 which may inadvertently fix the issue as well, in which case I'll at least let everyone here know if it does. Any further ideas or if anyone else has experienced this similar issue my ears are open. Thanks again Arun! J John Miller | Sr. Linux Systems Administrator <http://mybuys.com/> 530 E. Liberty St. Ann Arbor, MI 48104 Direct: 734.922.7007 http://mybuys.com/ <http://mybuys.com/> From: Arun C Murthy [mailto:a...@hortonworks.com] Sent: Thursday, December 15, 2011 2:03 PM To: mapreduce-user@hadoop.apache.org Subject: Re: Tasktracker Task Attempts Stuck (mapreduce.task.timeout not working) Hi John, It's hard for folks on this list to diagnose CDH (you might have to ask their lists). However, I haven't seen similar issues with hadoop-0.20.2xx in a while. One thing to check would be to grab a stack trace (jstack) on the tasks to see what they are upto. Next, try get a tcpdump to see if the tasks are indeed sending heartbeats to the TT, which might be the reason the TTs aren't timing them out. hth, Arun On Dec 15, 2011, at 7:58 AM, John Miller wrote: I've recently come across some interesting things happening within a 50-node cluster regarding the tasktrackers and task attempts. Essentially tasks are being created but they are sticking at 0.0% and it seems the 'mapreduce.task.timeout' isn't taking effect and they just sit there (for days if we let them) and the jobs have to get killed. Its interesting to note that the HDFS datanode service and HBASE regionserver running on these nodes work fine and we've been simply shutting down the tasktracker service on them in order to get around jobs stalling forever. Some historical information... We're running Cloudera's cdh3u0 release, and this has so far only happened on a handful of random tasktracker nodes and it seems to only effected those that have been taken down for maintenance and then brought back into the cluster, or alternatively one node was brought into the cluster after it had been running for a while and we ran into the same issue. After re-adding the nodes back into the cluster the tasktracker service starts getting these stalls. Also know that this has not happened to every node that has been taken out of service for a time and then re-added... I would say about 1/3'rd of them or so has ran into this issue after maintenance. The particular maintenance issues on the effected nodes were NOT the same, i.e. one was bad ram another was a bad sector on a disk etc... never the same initial problem only the same outcome after rejoining the cluster. It's also never the same mapred job that sticks, nor is there any time related evidence relating the stalls to a specific time of day. Rather the node will run fine for many jobs and then just all of a sudden some tasks will stall and stick at 0.0%. There are no visible errors in the log outputs, although nothing will move forward nor will it release the mappers for any other jobs to use until the stalled job is killed. It seems that the default 'mapreduce.task.timeout' just isn't working for some reason. Has anyone come across anything similar to this? I can provide more details/data as needed. John Miller | Sr. Linux Systems Administrator <image001.png> <http://mybuys.com/> 530 E. Liberty St. Ann Arbor, MI 48104 Direct: 734.922.7007 http://mybuys.com/ <http://mybuys.com/>
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