Push technology for Google's App Engine

Google has released version 1.4.0 of its App Engine SDK. For the first time, it allows a persistent bi-directional communication channel to be established between the parts of the application running in the browser and those on the server.

The Channel API responsible for this functionality is similar to the WebSockets functionality planned for HTML 5 in that it defines open, message, error and close events. These events are processed by client-side handler functions. Rather than a URL as in WebSockets, Google's API communicates via a channel generated by the server and standard HTTP POST requests.

In addition to this API, the App Engine SDK also now has an 'Always On' function, which reserves three instances of an application and never turns them off. This is intended to dispense with loading times for applications with low or variable traffic levels. The service costs $9 per month. It is also possible to set up 'Warm Up Requests' in an application's configuration file. These are intended to ensure that new instances are started in good time in response to increased data traffic.

Further information about the release can be found in the release notes. Version 1.4.0 of the Google App Engine SDK is available to download from Google Code.

See also:

• Google's App Engine now multi-tenant capable, a report from The H.

(crve)