Rackspace Hosting, the San Antonio, Texas, facilities provider that has geared its offerings to cloud computing, is making public an API that allows cloud users to write code that detects a workload in the cloud and scales up the number of servers meeting it as needed.

Rackspace said the API will remain open and standards-based and give cloud users greater control and flexibility in managing their workloads in the Rackspace cloud. The API is still in beta form and is known as the Rackspace Cloud Servers API.

Amazon also uses APIs to give its customers programmatic access to EC2, but those APIs are proprietary, not public. It has come under some pressure to make them public as the Eucalyptus project has duplicated its core APIs and made them available as open source code. The Amazon APIs for EC2, Elastic Block Storage, and S3 persistent storage have so far been matched by Eucalyptus.

"We're looking forward to working with the developer community to create a powerful cloud ecosystem, which we believe will generate new tools and applications," said Emil Sayegh, general manager of the Rackspace Cloud.

The Cloud Servers API was lauched earlier this year as a REST-based or representational state transfer Web service interface. Such interfaces are intended to be lightweight and fast in making Web services connections. Such services would share a common token system to allow a service to be authenticated as it is accessed by a user or another service.

Among other things, the API would include the ability to identify the type of virtualized server created through access to its metadata; an ability to inject files into the server file system before startup for configuration or other purposes; allow a customer to concentrate virtual servers on a host or set of hosts instead of having them automatically spread out over available hardware; and the ability to access a shared IP group, which might be used to access a high availability hardware cluster.

The new API allows Rackspace Cloud users to manage their servers off their iPhones, thanks to an iPhone application created by developer Michael Mayo, that makes use of the new API. It is expected to be available in the Apple App Store in the next 30 days.

"We see programmatic control as essential for igniting an ecosystem around the Rackspace Cloud," said Sayegh in the announcement.

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