AWS (Amazon Web Services) is pretty nice. It not only has what's needed to deploy and scale a web service, but everything can be controlled through their REST (or SOAP) API, so that everything can be automated.

One thing that should have been obvious was how a service would start when an instance starts. The first time, I created an instance from a prebuilt image, copied the code to it, then logged in and started it manually. Eventually, I created an image that included all the code. I finally figured out that I could start it in /etc/rc.local.

The next thing I needed to figure out was how to update the software. Everything would be in a single war file (except for static assets pushed up to the CloudFront CDN (Content Delivery Network)), but automatically building a new image from an existing image with the war file replaced looked difficult. I could do it manually by starting an instance, replacing the war file, and then creating a new image. I could automate that manual process. Another way seems to involve turning the image into a loopback filesystem, replacing the war file in the filesystem, then turning the filesystem back into an image, then uploading the image. Finally, I figured out that I could just upload the war file to Amazon S3 (Simple Storage Service), and the instance could download the war file from S3 when it starts up, and creating new images is unnecessary.

However, the process of getting a working image was slow and tedious, since starting and stopping instances, and creating images were all really slow. Once I had an image that worked, setting up load balancing was trivially easy. Setting up Auto Scaling also looks very easy, once I figure out what metrics to use for launching and terminating instances.