IPs are passed to the rack awareness script. We use 'dig' to do the reverse lookup to find the hostname, as we also embed the rack id in the worker node hostnames.

--Mike

On 11/18/2009 08:20 AM, David J. O'Dell wrote:
I'm trying to figure out if I should use ip addresses or dns names in my
rack awareness script.

Its easier for me to use dns names because we have the row and rack
number in the name which means I can dynamically determine the rack
without having to manually update the list when adding nodes.

However this won't work if the script is passed ips as arguments.
Does anyone know what is being passed on to the script(ip's or dns names)

Relevant docs:
http://hadoop.apache.org/common/docs/r0.20.1/cluster_setup.html#Hadoop+Rack+Awareness

and
http://hadoop.apache.org/common/docs/r0.20.1/api/org/apache/hadoop/net/DNSToSwitchMapping.html#resolve(java.util.List)





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