Cloud application programming interfaces

One of the key characteristics that distinguishes cloud computing from standard enterprise computing is that the infrastructure itself is programmable. Instead of physically deploying servers, storage, and network resources to support applications, developers specify how the same virtual components are configured and interconnected, including how virtual machine images and application data are stored and retrieved from a storage cloud. They specify how and when components are deployed through an API that is specified by the cloud provider.

An analogy is the way in which File Transfer Protocol (FTP) works: FTP servers maintain a control connection with the client that is kept open for the duration of the session. When files are to be transferred, the control connection is used to provide a source or destination file name to the server, and to negotiate a source and destination port for the file transfer itself. In a sense, a cloud computing API is like an FTP control channel: it is open for the duration of the cloud’s use, and it controls how the cloud is harnessed to provide the end services envisioned by the developer. The use of APIs to control how cloud infrastructure is harnessed has a pitfall: unlike the FTP protocol, cloud APIs are not yet standardized, so each cloud provider has its own specific APIs for managing its services. This is the typical state of an industry in its infancy, where each vendor has its own proprietary technology that tends to lock in customers to their services because proprietary APIs make it difficult to change providers.

Look for providers that use standard APIs wherever possible. Standard APIs can be used today for access to storage; APIs for deploying and scaling applications are likely to be standardized over time. Also look for cloud providers that understand their own market and provide, for example, ways to archive and deploy libraries of virtual machine images and preconfigured appliances.

Source of Information : Introduction to Cloud Computing architecture White Paper 1st Edition, June 2009


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