Recently, someone gave me some server space and root. I could do what I wanted to the server, as long as I kept the PHP and Drupal configurations working. While I at first was somewhat annoyed with it, being a fan of nginx and mongrel, I tried to install an Apache + Mongrel configuration, similar to what we deploy on other severs over and over again. The problem is that this was an Ubuntu server, therefore mod_php needs apache2-mpm-prefork to work, while mod_proxy needs apache2-mpm-worker. This will probably explain the oh-so-misleading error log:
[Mon Jun 02 18:01:26 2008] [warn] proxy: No protocol handler was valid for the URL /. If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule.
and the even worse
[Mon Jun 02 18:08:44 2008] [error] proxy: BALANCER: (balancer://mongrel_cluster). All workers are in error state
Of course, Google has told me that I wasn't running the right modules, while Ubuntu's documentation told me that I needed apache2-mpm-worker. After apt-getting the stuff, and realizing that the two are mutually exclusive, I decided to give passenger a try.
The setup is way simpler, but there are definitely some downsides to it. It appears that mod_rails is about as fast as mongrel so far (although I am not using it on a live environment), but when things go wrong, going through the trace stack is definitely a lot more painful. Also, another thing that I noticed is that with every deploy change, that I have to restart Apache now, which disrupts the other apps on the server. This is probably more of the case of getting your own box, but of course if I had my own box to play with, I wouldn't be using Apache.
Overall, if you are stuck sharing a box with some Drupal users, Passenger is your friend, since you won't have to explain why their PHP is now using FastCGI. It's clearly the path of least resistance as far as some Rails deployments go. This also means though that things like Capistrano will have to change to reflect this. I guess this is my assignment to lazyweb. Go find Cap scripts that deploy to Passenger. :P