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The Real-Time Web (and Other Buzzwords)

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The Real-Time Web (and Other Buzzwords)

  1. Chris Wanstrath http://defunkt.github.com hi everyone, i’m chris wanstrath
  2. i love randy rhoads
  3. and kurt vonnegut
  4. i live in san francisco
  5. and work at github
  6. (which is written in rails)
  7. but! i’m not gonna talk about any of that stuff
  8. today i want to talk about python
  9. and comet (among other things)
  10. the real-time web (And other buzzwords) By Chris Wanstrath this talk is titled “the real-time web (and other buzzwords)”
  11. so what is the “real-time” web? ?
  12. techcrunch and readwriteweb would have you believe it’s a way to get your RSS stories
  13. faster
  14. but is that it?
  15. no.
  16. it’s all about pushing
  17. instead of polling
  18. it’s getting told what’s new !
  19. ? instead of asking for what’s new
  20. instant chat in the browser
  21. and information the moment it’s available
  22. Server Client one persistent connection
  23. Client Server instead of many, short lived connections
  24. right now when we say “real-time web” we usually mean one of three things
  25. comet
  26. flash’s XMLSocket
  27. or HTML5’s WebSocket
  28. let’s start with comet
  29. ? how many people know what comet is? how many people know how it differs from XML socket or WebSocket? good! for a long time i had no idea what comet was
  30. i think it has a big marketing problem. !
  31. see, comet is a cleaning product.
  32. just like ajax
  33. so it’s kind of like,
  34. Me, too! “me too”
  35. I, too, am a revolutionary web technique you didn’t know existed and can start using today that will forever change the way you imagine the web experience. “I, too, am a revolutionary web technique you didn’t know existed and can start using today that will forever change the way you think about the web experience.”
  36. ... and you’re like
  37. Uhh... uh...
  38. AJAX!!!
  39. if i had my way...
  40. i’d call it something else
  41. like maybe asteroid
  42. i dunno, there’s some cool imagery there
  43. i dunno, there’s some cool imagery there
  44. i dunno, there’s some cool imagery there
  45. i dunno, there’s some cool imagery there
  46. i dunno, there’s some cool imagery there
  47. i dunno, there’s some cool imagery there
  48. i dunno, there’s some cool imagery there
  49. anything but comet
  50. anyway, comet is any standards compliant technique which pushes or streams data to the browser over HTTP with comet you can essentially fake a socket connection between a browser and a backend server
  51. how about an example well, for this year’s django dash
  52. me
  53. alex gaynor... whoops...
  54. alex gaynor
  55. and leah culver
  56. ( World’s smallest park ) (seen here next to the world’s smallest park)
  57. built leafychat irc in your browser using comet
  58. you can connect to freenode channels
  59. see who’s online
  60. and do the irc thing right in your browser (demo?)
  61. all without ajax
  62. how? ?
  63. well, there are a few components at play here
  64. Browser first you’ve got the browser (naturally)
  65. Browser Apache 80 then we have apache
  66. Django 8000 Browser Apache 80 sitting behind apache is django (via mod_wsgi or whatever)
  67. Django 8000 Browser Apache 80 the browser hits leafychat.com, port 80, which hits apache. apache sees it’s a django request
  68. Django 8000 Browser Apache 80 and hands off the request.
  69. Django 8000 Browser Apache 80 once django generates a response, apache takes it and delivers it
  70. Django 8000 Browser Apache 80 back to the browser. that’s, more or less, our HTTP request cycle
  71. Browser comet connections work in a similar fashion
  72. Browser Orbited 8100 instead of apache, we have Orbited sitting on port 8100
  73. orbited is an open source, python comet server powered...
  74. by twisted. it does all of the comet heavy-lifting for us
  75. Browser Orbited 8100 so.
  76. Zeddicus 8200 Browser Orbited 8100 sitting behind orbited we have our app-specific comet code. for leafy chat it was a twisted- based daemon named zeddicus. it handled all the IRC stuff - connecting to channels, sending messages, receiving private messages, logging, all that
  77. Orbited 8100 orbited handles generic browser stuff...
  78. Zeddicus 8200 while our app-specific daemon (zeddicus) deals with the business logic. in this case, irc stuff
  79. Zeddicus 8200 Browser Orbited 8100 does this look familiar?
  80. Django 8000 Browser Apache 80 no? ok.
  81. Zeddius Zeddicus 8200 Browser Orbited 8100 anyway, the browser (using orbited’s bundled js library) makes a request...
  82. Zeddius Zeddicus 8200 Browser Orbited 8100 to port 8100. orbited sees it’s a request for zeddicus and hands it off to our backend
  83. Zeddius Zeddicus 8200 Browser Orbited 8100 zeddicus sees a new socket connection open, does some stuff, then writes to the socket
  84. Zeddius Zeddicus 8200 Browser Orbited 8100 orbited reads what zeddicus wrote to the socket connection they share
  85. Zeddius Zeddicus 8200 Browser Orbited 8100 then sends it back the browser via comet
  86. Django 8000 Browser Apache 80 just like before
  87. <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> <head> <script> // session data var session_nick = "" var session_channels = [] </script> <script type="text/javascript" src="/static/js/soundmanager2/soundmanager2-nodebug-jsmin.js"></script <script type="text/javascript" src="/static/js/audio-player.js"></script> <title>Leafy Chat</title> <link rel="icon" href="/static/img/favicon.ico"/> <link rel="stylesheet" href="/static/css/reset.css" type="text/css" media="screen" /> <link rel="stylesheet" href="/static/css/facebox.css" type="text/css" media="screen/> <link rel="stylesheet" href="/static/css/base.css" type="text/css" media="screen" /> <script> document.domain = document.domain; </script> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"> <script type="text/javascript" src="http://leafychat.com:8100/static/Orbited.js"></script> <script type="text/javascript" src="/static/js/facebox.js" charset="utf-8"></script> <script type="text/javascript" src="/static/js/cookie.js" charset="utf-8"></script> <script type="text/javascript" src="/static/js/leafy.js" charset="utf-8"></script> <script type="text/javascript" src="/static/js/kahlan.js" charset="utf-8"></script> <div id="main"> <div id="header"> <div id="navigation" class="rounded"> <ul class="nav-list"> <!-- this should be a list --> <li>Hi <span id="welcome-user">there</span>!</li> but while apache and django deal with html
  88. Zeddius Zeddicus 8200 Browser Orbited 8100 zeddicus, our back-end daemon, concerns itself only...
  89. with json. orbited supports STOMP, XMPP, and raw IRC, too, but JSON is the way to go. why do i say that?
  90. well, unfortunately this is where orbited does not rock
  91. orbited only cares about giving you a socket, you have to do everything else yourself. that’s the deal
  92. so you need to design your own protocol...
  93. how it interacts with your back-end daemon
  94. how events are fired and responded to
  95. all that boring stuff
  96. we ended up using a combination of django signals and json
  97. Zeddius Zeddicus 8200 Browser Orbited 8100 so this is our overview, except with one small change
  98. Zeddius Zeddicus 8200 Browser Orbited 8100 these are actually persistent connections
  99. Zeddius Zeddicus 8200 Browser Orbited 8100 between orbited and zeddicus it’s a tcpsocket
  100. Zeddius Zeddicus 8200 Browser Orbited 8100 between the browser and orbited it’s a comet technique
  101. Zeddicus Browser 8200 we jump through all these hoops because it allows us to write our app as if the browser is connecting DIRECTLY to zeddicus via a tcpsocket
  102. Zeddicus Browser 8200 which is what the “real time” web is all about and what comet gives us the browser writes to and reads from a socket, our back-end daemon does the same.
  103. fast communication
  104. Zeddius Zeddicus 8200 Browser Orbited 8100 alright, so let’s talk about this part a bit more the comet part
  105. Zeddius Zeddicus 8200 Browser Orbited 8100 there are a few different ways to fake a persistent connection to a server with modern browsers
  106. xhr long polling - hang an xhr request until we get a response or 30s, then re-open and wait again
  107. <script> script tag long polling - dynamically create a script tag pointing to a url that hangs or times out, rinse and repeat
  108. <iframe> forever frame - open a Content-Encoded: chunked url in an iframe, each chunk is a <script> tag that runs
  109. xhr streaming - set content-encoding: chunked and trigger onreadystate callback with each chunk
  110. so now you know our white lie: we don’t have real persistence, or a real socket. we fake it at both ends.
  111. or, really, orbited fakes it at both ends
  112. all that to get irc in your browser
  113. well, kinda
  114. Zeddius freenode Zeddicus 8200 6667 Browser Orbited 8100 see, with orbited, you can connect directly to an irc server and why not? it’s just a socket connection
  115. in fact you can demo a (somewhat functional) irc connection on the orbited website
  116. Zeddius Zeddicus 8200 Browser Orbited 8100 Zeddius freenode Zeddicus 8200 6667 but with leafychat we wrote our own backend daemon that connected to irc. why?
  117. logging.
  118. Zeddius Zeddicus 8200 Browser Orbited 8100 if we loaded our django code into zeddicus, we could easily log irc chats you’re interested in based on your session id. it works very well.
  119. Django Orbited 8000 Browser Apache 80 Zeddius 8200 at this point i should mention the older tutorials online explaining how to load orbited into django.
  120. Apache Django 80 8000 Browser Orbited Zeddicus 8100 8200 but i the best (and simplest) way is to let each component be its own daemon it works great for production as well as dev mode - the django dash judges were able to start and run our app locally, despite the number of daemons that needed to run
  121. if you want to get a comet app up and running locally, check out orbited it supports a ton of comet transports and is actively maintained
  122. using java? jetty has comet support
  123. the ruby world has juggernaut
  124. while perl has meteor
  125. there’s the interesting in-progress Ajax Push Engine
  126. and in erlang there’s erlycomet (built on mochiweb)
  127. so, flash’s XMLSocket
  128. Zeddius Zeddicus 8200 Browser Orbited 8100 it turns this
  129. Zeddicus Browser 8200 into this
  130. how? flash allows you to make tcp connections in actionscript. by providing a javascript api to those tcp connections, we can use flash to create persistent, socket connections from the browser
  131. no lying needed
  132. of course, it may be non-standard and might not work great across firewalls. but if you can use it, it’s pretty great
  133. a popular technique is to attempt to open a flash socket, then fall back to standards based comet methods if it fails it’s good backup
  134. there are a few nice libraries for xml socket on github
  135. tmm1 / jssocket my favorite is tmm1’s jssocket
  136. defunkt / jssocket (i have a fork which removes the jquery dependencies)
  137. finally: HTML5’s WebSocket
  138. it’s still a proposed draft but it’ll let you open a socket to any serve that speaks the special WebSocket protocol
  139. ws:// servers need to speak the WebSocket protocol - you can’t open arbitrary connections to irc or xmpp gateways this plugs up the obvious security holes but also makes it a bit harder to implement than something like XMLSocket your server needs to speak ws
  140. so, in review ?
  141. comet
  142. should be called asteroid
  143. flash’s XMLSocket
  144. is non-standard but nice
  145. HTML5’s WebSocket
  146. not yet here but futuristic
  147. you should give orbited a shot
  148. with json
  149. 0 probably null terminated
  150. Django Orbited 8000 don’t load orbited in django
  151. Orbited 8100 use them alongside each other
  152. is that it? ?
  153. that’s it !
  154. Thank You
  155. http://www.flickr.com/photos/mojombo/3785549701/sizes/l/ http://www.flickr.com/photos/voteprime/2361330726/sizes/o/ http://www.flickr.com/photos/johnkerr/2371310025/sizes/l/ http://www.flickr.com/photos/h19/182898904/ http://www.flickr.com/photos/ukinindia/3595042998/sizes/l/ http://www.flickr.com/photos/scott1027/3189137578/sizes/l/ http://www.flickr.com/photos/foxypar4/2124673642/sizes/l/ http://www.flickr.com/photos/nickwheeleroz/2166114756/sizes/l/ http://www.flickr.com/photos/nickwheeleroz/2178146080/sizes/l/ http://www.flickr.com/photos/diyromarcade/3006368260/sizes/o/ http://www.flickr.com/photos/boopsiedaisy/3611187885/sizes/o/ http://www.flickr.com/photos/bastispicks/2834869959/sizes/l/ http://www.flickr.com/photos/courtenay/2536259393/sizes/l/ http://www.flickr.com/photos/jardinle/3335907363/sizes/o/ http://www.flickr.com/photos/tim-miley/3569809538/ http://www.flickr.com/photos/dexterousartisan/3209508363/sizes/l/ http://www.flickr.com/photos/equanimity/3763158824/sizes/l/ http://www.flickr.com/photos/24617281@N04/2329660856/sizes/o/ http://farm4.static.flickr.com/3555/3767120120_8f43f885e1.jpg http://www.flickr.com/photos/raffaella/64701476/ http://www.flickr.com/photos/monicareyes/405402858/sizes/o/ http://www.flickr.com/photos/11016633@N07/2232831953/ flickr