Scalr is an open source alternative to RightScale. It is a Cloud management tool that allows you to host applications on the Cloud through a web-based interface.


Company: Cloud in Code
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Amazon Web Services Used: Amazon Simple Queue Service (Beta)
Solution URL:
Audience: Developers
Pricing: For a fee
How does this application use Amazon Web Services?: Scalr uses EC2 for its Web, App, and DNS servers, and S3 to store its custom AMIs, scripts, and plugins.
Created On: June 23, 2009 8:21 PM GMT
Last Updated: July 2, 2009 7:25 PM GMT
Scalr is an open source alternative to RightScale.

It is a fully redundant, self-curing and self-scaling hosting environment utilizing Amazon's EC2.

It allows you to create server farms through a web-based interface using prebuilt AMI's for load balancers (pound, nginx, or Amazon's load balancing service), app servers (apache, rails, etc.), databases (mysql master-slave, others), and a generic AMI to build on top of.

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.

Multiple 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.

While the project has matured a lot in 2 years, we're hoping that by open sourcing it, the AWS development community will contribute towards making it a premier hosting platform and give users an alternative to the current fee based services available.

Scalr is now available as a pay service at
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