Tomcat 6 / Apache 2.2 Cluster Issue

["Alston, Brian (US SSA)" <br...@baesystems.com>]

I have one Apache http server version 2.2.3  (on Red Hat Enterprise Linux 5) and three Tomcat 6 servers (on Windows Server 2003) running in my cluster. Everything "appears" to be working well. It looks like it is using RoundRobin because every time I refresh the page it goes from web001 -> web002 -> web003 -> web001 -> etc. I used some of the examples that are provided with Tomcat in the "examples" directory - specifically the "Sessions" servlet and it looks like my sessions are staying the same and holding information. My issue is this. When I stop one of the Tomcat servers (let's say web002), I will sometimes get the following error message when I refresh the page:

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Proxy Error

The proxy server received an invalid response from an upstream server.
The proxy server could not handle the request GET /examples/instance.html.

Reason: Error reading from remote server

Apache/2.2.3 (Red Hat) Server at 150.37.0.20 Port 80

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I don't get this error message every single time I refresh the page but I do get it often. It looks like Apache http server is still trying to access the Tomcat server web002 even though it is down. Does this sound like I have an incorrect configuration to anybody or is this normal? I would not think that it was normal, as clustering is supposed to prevent errors like this.

I have been following the examples in the O'Reilly book "Tomcat: The Definitive Guide" in chapter 10 - "Tomcat Clustering".

Any help anybody can provide will be greatly appreciated.

Thank you for reading, have a good day.
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