Google App Engine Adds Comet Support

by Dylan SchiemannDecember 3rd, 2010

Per the recent announcement on the Google App Engine Blog, app engine now supports a Comet API:

The Channel API - A bi-directional channel for communicating directly with user browsers by pushing notifications directly to the JavaScript running on the client, eliminating the need for polling. This service makes it easy to build real-time applications such as multi-player games, chat rooms, or any collaboration centric app and is built on the same Google infrastructure that powers Google Talk.

2 Responses to “Google App Engine Adds Comet Support”

  1. James Mortensen Says:

    Hi Dylan,

    I put together a chat demo of the ChannelAPI, located here:

    Using Firebug, you can see that the resulting comet connection is with the server. Yet any messages that I send are sent to a servlet on my application and not through an API “publish” mechanism.

    It’s still two-way communication, but I think it’s worth pointing out that Google should create an interface or wrapper around the message send calls so that when the ChannelAPI Comet functionality is replaced with WebSockets functionality we all won’t have to upgrade our message sending code to use a “publish” API instead of making AJAX calls directly to our application.

    Dojo is setup using the Bayeux protocol publish/subscribe model. This allows the Dojo developers to swap out the behind-the-scenes business logic with a WebSocket/Comet fallback mechanism. I really think Google’s API could benefit by following this same standard.

    The “publish” function does not appear to exist in the ChannelAPI. Although I’m really excited to see comet available on App Engine, we need to get the actual “sending” mechanism bound to a socket.publish() method so that developers can seamlessly switch between Comet and WebSockets.

    In this area, the Dojo development team definitely made the right architectural decisions, and I encourage you to share your experiences with the Google ChannelAPI team.

    Thank you,

  2. DylanSchiemann Says:


    Thanks for digging deeper into Google’s API and for making points which I of course agree with. I’ll make sure your feedback gets back to them, if they haven’t seen it already.


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