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From Christopher Schultz <>
Subject Re: Different apps clustering on the same Tomcat?
Date Thu, 21 Jan 2010 15:21:49 GMT
Hash: SHA1


On 1/20/2010 10:28 PM, John Tangney wrote:
> We use a cluster to do seamless deploys. We use Nginx on the front end
> to direct traffic to one or other of the nodes in the cluster. To
> deploy, we bring up the new version of the app in a one node, tell Nginx
> to send traffic to that node, then bring down the other node. Because
> sessions are propagated, users never notice that one node has been
> exchanged for another.

Careful: if you change the definition of any of the classes whose
objects are in the session, you'll get a nasty replication error
(because de-serialization will fail). Be careful with anything you
modify that might be lurking in a user's session.

> We need to add two more nodes that run on Windows (we have
> platform-specific code, and Nginx sends windows traffic to one of the
> windows nodes based on URL) but we only have one Windows box. We thought
> that perhaps we could just run a second instance of the app on the
> Windows node.
> From what you said previously, this does not appear to be possible. So
> we'll be looking new hardware.

Oh, you can certainly do it. Knowing why you want to do it certainly
helps clear things up. I'm still as confused as Chuck is, though :)

- -chris
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