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From Doug Cutting <cutt...@apache.org>
Subject Re: map task in initializing phase for too long
Date Thu, 21 Jun 2007 16:21:13 GMT
Jun Rao wrote:
> I am wondering if anyone has experienced this problem. Sometimes when I 
> ran a job, a few map tasks (often just one) hang in the initializing phase 
> for more than 3 minutes (it normally finishes in a couple seconds). They 
> will eventually finish, but the whole job is slowed down considerably. The 
> weird thing is that the slow task is not deterministic. It doesn't always 
> occur and if does, can occur on any split and on any host.

I have not seen this.

Perhaps you can get a stack trace from the tasktracker while this is 
happening?

Owen described how to get such stack traces in:

http://mail-archives.apache.org/mod_mbox/lucene-hadoop-user/200706.mbox/%3c3AB557D4-4B71-4286-BB36-1A449F28BAD5@yahoo-inc.com%3e

Owen wrote:
> One side note is that all of the servers have a servlet such that if  
> you do http://<node>:<port>/stacks you'll get a stack trace of all  
> the threads in the server. I find that useful for remote debugging.  
> *smile* Although if it is a task jvm that has the problem, then there  
> isn't a server for them.

(This should probably be added to the documentation or the wiki...)

Doug

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