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From Brian Bockelman <bbock...@cse.unl.edu>
Subject Re: Hadoop+log4j
Date Mon, 24 Nov 2008 15:56:02 GMT

On Nov 24, 2008, at 9:49 AM, Steve Loughran wrote:

> Scott Whitecross wrote:
>> Thanks Brian.  So you have had luck w/ log4j?
> We grab logs off machines by not using lo4j and routing to our own  
> logging infrastructure that can feed events to other boxes via RMI  
> and queues. This stuff slots in behind commons-logging, with a  
> custom commons-logging bridge specified on the command line. To get  
> this into Hadoop I had to patch hadoop.jar and remove the properties  
> file that bound it only to log4j. The central receiver/SPOF logs  
> events by sent time and received time and can store all results into  
> text files intermixed for post-processing. It's good for testing,  
> but on a big production cluster you'd want something more robust and  
> scaleable

Hey Steve,

Sounds like a cool setup, but might be a little much for Scott's  
purposes (trying to debug a single Map phase...).  Scott, I have been  
able to successfully add new log4j loggers, but in Hadoop code, not in  
a M-R task.  If you try things in local mode, you'll be guaranteed to  
have the same JVM, so the configuration should be loaded the same way.

Then again, I might be putting words into Scott's mouth: maybe he does  
indeed want to scale this way up and turn it into a "logging  

Scott, did you have any luck debugging the job through the wiki  
document on debugging mapreduce?  I'd make sure to start there before  
you take too much of a detour into log4j-land.


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