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From Chris Dean <ctd...@sokitomi.com>
Subject Re: webhcat: running callbacks when one webhcat server goes down.
Date Thu, 02 May 2013 01:22:03 GMT
Andrew Mains <andrew.mains@kontagent.com> writes:
> 1. Start up two webhcat instances, server1 and server2.
> 2. Submit a query to server1 with a callback.
> 3. Kill server1
>
> The callback was never received in this case.
>
> Is this the expected behavior?

That is not the expected behavior.  If you wish to setup multiple
webhcat servers here are a few things to check:

1. Configure the storage engine used to store the job information.  The
   config vars are templeton.storage.class and templeton.storage.root

   The defaults are fine, but if you use HDFS (the default) make sure
   that the webhcat servers are actually writing to
   templeton.storage.root (which is "/templeton-hadoop" by default).

2. Make sure that you are accessing your servers using a common url.
   For example, you might have a load balancer at
   http://webhcat.mydomain.com that points to your http://server1 and
   http://server2

   The common url must also be accessible from the JobTracker.

   The common url is needed because the JobTracker notifies webhcat that
   the job has been completed by accessing the webhcat server using this
   url.

I'm not sure if this is documented anywhere and I'm afraid the
information logged is of little help.

Cheers,
Chris Dean


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