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From Adam DeConinck <adeconi...@rsystemsinc.com>
Subject NameNode not registering DataNodes for unknown reason
Date Tue, 16 Aug 2011 19:48:28 GMT
Hi all,

I've been seeing an HDFS issue I don't understand, and I'm hoping
someone else has seen this before.

I'm currently attempting to set up a simple-stupid Hadoop
test cluster on two Dell PE1950s running a minimal installation of RHEL
5.6.  The master node, wd0031, is running a NameNode, DataNode and
SecondaryNameNode.  A single slave node, wd0032, is running a DataNode. 
The Hadoop processes are starting up fine and I'm not seeing any errors
in the log files; but the DataNodes never join the filesystem.  There
are never any log entries in the NameNode about their registration,
doing a "hadoop fsck /" lists zero data-nodes, and I can't write files. 
The config and log files, and some ngrep traces, are up on
https://gist.github.com/1149869 .

What's weird is that exactly the same configuration works on a two-node
EC2 cluster running CentOS 5.6: the filesystem works, fsck lists the
datanodes, and the logs show the right entries.  See
https://gist.github.com/1149823 .  As far as I can tell there should be
no difference between these cases.

Jstack traces on a DataNode and NameNode for both cases, local and EC2,
are here: https://gist.github.com/1149843

I'm a relative newbie to Hadoop, and I cannot figure out why I'm having
this problem on local hardware but not EC2.  There's nothing in the logs
or the jstacks which is obvious to me, but hopefully someone who knows
Hadoop better can let me know.

Please feel free to let me know if you need more information.


Adam DeConinck | Applications Specialist | adeconinck@rsystemsinc.com

Enabling Innovation Through Fast and Flexible HPC Resources

R Systems NA, inc. | 1902 Fox Drive, Champaign, IL 61820 | 217.954.1056 | www.rsystemsinc.com

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