Growing a larger server farm
Adding new machines
Adding a new machine to a cluster is simple. The key step is to update each frontend Load Balancer so that it is aware of this extra machine, and so can distribute HTTP requests to it. Follow these instructions to add the new machine:
First, you must install the Zeus Webserver on the new machine in the cluster. Follow the same instructions described in the original cluster installation documentation (do not forget to set up the webserver in 'clustered' mode).
Next, go to the Adminserver for the cluster and select the 'clustering' button. Then select the 'configuration' option at the bottom of the page, underneath the network layout diagram. From here, enter the new details of the machine being added into the cluster.
You will also need to copy from the adminserver the $ZEUSHOME/webadmin/conf/hosts file. This is a simple text file that contains information on the back-end webservers that are in the system. The front-end machines need to know this information so they know which back-end machines are available to them to send their requests to. Copy the file $ZEUSHOME/webadmin/conf/hosts from the admin machine to $ZEUSHOME/balancer/workers on the front-end machines.
There is no need to restart the Load Balancers - they will notice that the workers file has been updated, and will add the new machine into the cluster automatically. Use the Adminserver to check that the new machine is receiving requests and is functioning correctly.
Troubleshooting
If there are problems, the first place to look is the error log on the Load Balancers. This file is found in $ZEUSHOME/balancer/log/errors. Warning messages will be printed if the Balancer cannot find the backend machine. Also, check the 'summary' page on the admin server - theres a link to it from the cluster network layout page. The summary page gives a brief diagnosis of your clustered setup, and can spot many common configuration problems.