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From Fredrik Möllerstrand <fred...@mollerstrand.se>
Subject HMaster and /etc/hosts
Date Mon, 15 Jun 2009 17:00:07 GMT
Hello list!

I've spent the better part of the afternoon upgrading from 0.19.3 to
trunk, and I did fall into a hole or two. Specifically, it turns out
that we rely on DNS lookups to find out what address HMaster binds to,
which caused me some grief. The documentation is also weak on what
part Zookeeper plays in the process; a stronger write-up of how HBase
utilizes Zookeeper would be a great help in troubleshooting issues
like this.

Basically, I saw the region servers trying to connect to
127.0.0.1:6000 without any hint as to why, neither in the (default)
configuration nor the logs.

HMaster happily reported this:
INFO org.apache.hadoop.hbase.master.HMaster: My address is
master2.internal.net:6000
quickly followed by:
INFO org.apache.hadoop.hbase.master.HMaster: HMaster initialized on
127.0.0.1:6000

The cause was simple and my face-palm genuine as the realization
struck me: there was a record for master2 in the hosts file, and it
was pointing to 127.0.0.1.

I suggest that an hbase.master.address option (that overrides any
resolved address) would make it easier to get the installation up and
running.


Cheers,
Fredrik

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