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Cometd / ShortBus Slide Presentation
 

Cometd / ShortBus Slide Presentation

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Cometd / ShortBus Slide Presentation (PowerPoint)

Cometd / ShortBus Slide Presentation (PowerPoint)

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    Cometd / ShortBus Slide Presentation Cometd / ShortBus Slide Presentation Presentation Transcript

    • ShortBus HTTP based event system
    • What is ShortBus
      • Perlbal plugin (reproxy service)
      • Suite of libraries
        • JavaScript
        • Perl
      • ShortBus is funny name for a serious project
    • Perlbal Plugin
      • Runs as a perlbal proxy service
      • Browser connects to shortbus without user interaction
      • Long lived connections
      • 1 minute event queue with lazy acknowledgments. (configurable)
      • Event replay (starting at an event id)
    • JavasScript Library
      • Continuous IFrame
        • Firefox
          • Loading Icon problem (may use xmlhttp instead)
        • IE
          • Htmlfile trick
            • htmlfile object with iframe inside
            • Gets around IE *click*
      • Xmlhttp
        • Firefox, IE, Others
          • Needs to be reused more often to avoid using large amounts of memory
    • Perl Modules
      • ShortBus
        • Contains Perlbal plugin, utils
        • Will contain examples
          • Chat server
          • Web server
          • Client monitor
    • Connection Process
      • Browser connects to Perlbal
        • http://[ random].example.com/shortbus
      • Perlbal requests /shortbus from web server
      • Web server script authorizes request by sending 2 headers:
        • X-REPROXY-SERVICE: shortbus
        • X-SHORTBUS: ID=55B4C1EC-DBBC-11DA-8F28-BEE8F8B0946C; action=bind; channels=foo,bar;
      • Web server stores Perlbal server and client ID for future use
      • Perlbal redirects request to shortbus plugin, and events start streaming
    • Benefits of ShortBus
      • Normal authorization techniques can be used
        • Basic, Digest, etc
        • Cookie based
      • Cookies can be processed normally
      • The web server authorizes each client connection to enter the event system
      • Perlbal can handle the large amount of open connections
      • Uses standard JSON
        • Pluggable
          • Atom, YAML, etc
    • Client Posts
      • Client sends POST data
      • Web server processes it normally
      • Can ack events by returning 2 headers:
        • X-REPROXY-SERVICE: shortbus
        • X-SHORTBUS: ID=55B4C1EC-DBBC-11DA-8F28-BEE8F8B0946C; action=ack; eid=<event id>
      • Shortbus returns data normally (does not enter event loop)
      • Transparent to the client
    • Potential Uses
      • Live chat
      • Stock ticker
      • Live website updates
        • Same user, two browsers
        • (Delete asset on one, dissapears on the other)
      • Games
        • Card games (Texas Hold’em  )
        • Ajax MMORPG! (VRML anyone?)
    •