Reverse Proxy dynamic webserver loading

Question

Is there any way to dynamically load and unload webservers from a reverse proxy?

For example let's say I have a cluster of 100 apache servers and I want to patch the servers. I would like the have a setup where I have a pool of updated servers and a pool of "being updated" servers. I would like the reverse proxy be aware of what is being patched and not read from these webservers.

I don't want to use just a config file to configure the reverse proxy.

Answer 1

You can use varnish's backend polling. You put simple check script on each server in backend and let varnish to poll it. Each poll will mean asking some "master server" if "slave" has got right version, enough disk space etc...