Scalr - Open Source Auto-scaling Hosting on Amazon EC2

Scalr is a fully redundant, self-curing and self-scaling hosting environment utilizing Amazon's EC2. It has been recently open sourced on Google Code.

Scalr allows you to create server farms through a web-based interface using prebuilt AMI's for load balancers (pound or nginx), app servers (apache, others), databases (mysql master-slave, others), and a generic AMI to build on top of.
Scalr promises automatic high-availability and scaling for developers by health and load monitoring.

The health of the farm is continuously monitored and maintained. When the Load Average on a type of node goes above a configurable threshold a new node is inserted into the farm to spread the load and the cluster is reconfigured. When a node crashes a new machine of that type is inserted into the farm to replace it.

4 AMI's are provided for load balancers, mysql databases, application servers, and a generic base image to customize. Scalr allows you to further customize each image, bundle the image and use that for future nodes that are inserted into the farm. You can make changes to one machine and use that for a specific type of node. New machines of this type will be brought online to meet current levels and the old machines are terminated one by one.

The open source scalr platform with the combination of the static EC2 IP addresses makes elastic computing easier to implement. Check out the blog announcement by Intridea for more info.

As AWS conquers the scalable web application hosting space it is time to check out the new
Programming Amazon Web Services: S3, EC2, SQS, FPS, and SimpleDB (Programming)

book on

What do you think of the opportunities of using scalr for automatic scalability?