I don't know if I've written about it here or not, but I have spent some time over the past couple of months contributing to an open source project started by Chris Richardson, of "POJOs in Action" fame, called Cloud Tools. It's a set of tools to launch Java based web applications onto Amazon EC2. I've been in charge of moving a lot of the functionality that exists in Maven commands over to Gant scripts for use with Grails. It's pretty rad.
You can launch your Grails application onto a server by simply typing: "grails cloud-tools-deploy". It support all sorts of clustering and master/slave arrangements with DBs and so forth... totally rad.
Anyway, back in October my company, -yoink-, got the go ahead from our client to run one of our web sites on EC2 -yoink-. I elected to use Cloud Tools because it looked great, and I had read Chris's book in the past, so I knew it would be quality.
I can't tell you how much time it saves to be able to bootstrap a server from the command line with a simple "grails cloud-tools-deploy" If you've built any web sites then you know what a pain in the ass deployment is, and you know what a pain in the ass server configuration is. Cloud Tools and EC2 eliminate the need for both and allows you to focus on what you're good at: writing code.
Continuing... today we had a massive email drop, which drove a ton of traffic to the site, that I had no idea was going to happen. The only way I found out is an external monitoring service I had hooked up alerted me to the fact that my server was unable to serve pages. The solution was as simple as opening my app, changing the config to run with 4 app servers, and running "grails cloud-tools-deploy." Once deployed, I switched the Elastic IP address of the old deployment to the load balancing server of my new deployment and voila! My site was hauling ass again.
Had we been using the traditional managed hosting services that we typically use, like those offered by Rackspace, we'd have been totally screwed. It would have taken them at least a week to get another server up and running, which would have been way too long. Using EC2 and Cloud Tools, I simply started servers as I needed them, and I'll shut them down tomorrow when the traffic dies down. It will probably only cost our client about $20 at the most, and think of the time and money that would have been lost if the server configuration had not been able to handle the load being thrown at it.
EC2 is pretty rad.