Developing Revolutionary Web Applications using Comet and Ajax Push

Developing Revolutionary Web Applications using Comet and AjaxDoris Chen Ph.D.Staff Engineer/Technology Evangelist1Agenda" Web 2.0• Introduction to Comet• Asynchronous HTTP and the Server• Develop a Slideshow Chat Application using Cometd (demo)• Develop a Two Player Game using Comet (demo)• Future, Summary and Resources2Web 2.0A Web by the people, for the people.Documents on the web increasingly generated by usersOut of the Information Age, into the Participation Age Are web user interfaces becoming more powerful?Is the user an HTTP client?3The Asynchronous Web RevolutionThe Web enters the Participation Age.• Ajax is still typically synchronous with user events• Full asynchrony has updates pushed from server any time> Update pages after they load> Send users notifications• Al ow users to communicate and collaborate within the web application• Cal ed “Ajax Push”, “Comet”, or “Reverse Ajax”> This is the ful realization of Ajax, now ful y asynchronous4Applications in the Participation AgeApplication-mediated communication.• Distance learning• Col aborative authoring• Auctions• Shared WebDAV filesystem• Blogging and reader comments• SIP-coordinated mobile applications• Hybrid chat/email/discussion forums• Customer assistance on sales/support pages• Multi-step business process made col aborative• Shared trip planner or restaurant selector with maps• Shared calendar, “to do” list, project plan• Games5Agenda• Web 2.0• Introduction to Comet• Asynchronous HTTP and the Server• Develop a Slideshow Chat Application using Cometd (demo)• Develop a Two Player Game using Comet (demo)• Future, Summary and Resources6Server-mediated CollaborationExternal ApplicationServer• User InitiatedUserPushPushAction• Application InitiatedClient 1Client 2, 3, ..n7What is Comet (Ajax Push)?Responsive, low-latency interaction for the web• A programming technique that enables web servers to send data to the client without having any need for the client to request for it• Al ows creation of highly responsive, event-driven web applications > Keep clients up-to-date with data arriving or changing on the server, without frequent pol ing• Pros> Lower latency, not dependent on pol ing frequency> Server and network do not have to deal with frequent pol ing requests to check for updates8Ajax Poll vs Ajax PushBending the rules of HTTP.• Comet Refers to both the Long Pol ing and Streaming methods of web programming9Ajax Poll vs Ajax PushBending the rules of HTTP.• Poll: > Send a request to the server every X seconds > The response is “empty” if there is no update• Long Pol : (most popular, demo use)> Send a request to the server, wait for an event to happen, then send the response> The response is never empty• Http Streaming: > Send a request, wait for events, stream multi-part/chunked response, and then wait for the events> The response is continual y appended to10