The Real-Time Web (and Other Buzzwords)

Chris Wanstrath http://defunkt.github.com hi everyone, i’m chris wanstrath

i love randy rhoads

and kurt vonnegut

i live in san francisco

and work at github

(which is written in rails)

but! i’m not gonna talk about any of that stuff

today i want to talk about python

and comet (among other things)

the real-time web (And other buzzwords) By Chris Wanstrath this talk is titled “the real-time web (and other buzzwords)”

so what is the “real-time” web? ?

techcrunch and readwriteweb would have you believe it’s a way to get your RSS stories

faster

but is that it?

no.

it’s all about pushing

instead of polling

it’s getting told what’s new !

? instead of asking for what’s new

instant chat in the browser

and information the moment it’s available

Server Client one persistent connection

Client Server instead of many, short lived connections

right now when we say “real-time web” we usually mean one of three things

comet

ﬂash’s XMLSocket

or HTML5’s WebSocket

let’s start with comet

? 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

i think it has a big marketing problem. !

see, comet is a cleaning product.

just like ajax

so it’s kind of like,

Me, too! “me too”

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.”

... and you’re like

Uhh... uh...

AJAX!!!

if i had my way...

i’d call it something else

like maybe asteroid

i dunno, there’s some cool imagery there

anything but comet

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

how about an example well, for this year’s django dash

me

alex gaynor... whoops...

alex gaynor

and leah culver

( World’s smallest park ) (seen here next to the world’s smallest park)

built leafychat irc in your browser using comet

you can connect to freenode channels

see who’s online

and do the irc thing right in your browser (demo?)

all without ajax

how? ?

well, there are a few components at play here

Browser ﬁrst you’ve got the browser (naturally)

Browser Apache 80 then we have apache

Django 8000 Browser Apache 80 sitting behind apache is django (via mod_wsgi or whatever)

Django 8000 Browser Apache 80 the browser hits leafychat.com, port 80, which hits apache. apache sees it’s a django request

Django 8000 Browser Apache 80 and hands off the request.

Django 8000 Browser Apache 80 once django generates a response, apache takes it and delivers it

Django 8000 Browser Apache 80 back to the browser. that’s, more or less, our HTTP request cycle

Browser comet connections work in a similar fashion

Browser Orbited 8100 instead of apache, we have Orbited sitting on port 8100

orbited is an open source, python comet server powered...

by twisted. it does all of the comet heavy-lifting for us

Browser Orbited 8100 so.

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

Orbited 8100 orbited handles generic browser stuff...

Zeddicus 8200 while our app-speciﬁc daemon (zeddicus) deals with the business logic. in this case, irc stuff

Zeddicus 8200 Browser Orbited 8100 does this look familiar?

Django 8000 Browser Apache 80 no? ok.

Zeddius Zeddicus 8200 Browser Orbited 8100 anyway, the browser (using orbited’s bundled js library) makes a request...

Zeddius Zeddicus 8200 Browser Orbited 8100 to port 8100. orbited sees it’s a request for zeddicus and hands it off to our backend

Zeddius Zeddicus 8200 Browser Orbited 8100 zeddicus sees a new socket connection open, does some stuff, then writes to the socket

Zeddius Zeddicus 8200 Browser Orbited 8100 orbited reads what zeddicus wrote to the socket connection they share

Zeddius Zeddicus 8200 Browser Orbited 8100 then sends it back the browser via comet

Django 8000 Browser Apache 80 just like before

<!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">  <li>Hi <span id="welcome-user">there</span>!</li> but while apache and django deal with html

Zeddius Zeddicus 8200 Browser Orbited 8100 zeddicus, our back-end daemon, concerns itself only...

with json. orbited supports STOMP, XMPP, and raw IRC, too, but JSON is the way to go. why do i say that?

well, unfortunately this is where orbited does not rock

orbited only cares about giving you a socket, you have to do everything else yourself. that’s the deal

so you need to design your own protocol...

how it interacts with your back-end daemon

how events are ﬁred and responded to

all that boring stuff

we ended up using a combination of django signals and json

Zeddius Zeddicus 8200 Browser Orbited 8100 so this is our overview, except with one small change

Zeddius Zeddicus 8200 Browser Orbited 8100 these are actually persistent connections

Zeddius Zeddicus 8200 Browser Orbited 8100 between orbited and zeddicus it’s a tcpsocket

Zeddius Zeddicus 8200 Browser Orbited 8100 between the browser and orbited it’s a comet technique

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

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.

fast communication

Zeddius Zeddicus 8200 Browser Orbited 8100 alright, so let’s talk about this part a bit more the comet part

Zeddius Zeddicus 8200 Browser Orbited 8100 there are a few different ways to fake a persistent connection to a server with modern browsers

xhr long polling - hang an xhr request until we get a response or 30s, then re-open and wait again

xhr streaming - set content-encoding: chunked and trigger onreadystate callback with each chunk

so now you know our white lie: we don’t have real persistence, or a real socket. we fake it at both ends.

or, really, orbited fakes it at both ends

all that to get irc in your browser

well, kinda

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

in fact you can demo a (somewhat functional) irc connection on the orbited website

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?

logging.

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.

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.

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

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

using java? jetty has comet support

the ruby world has juggernaut

while perl has meteor

there’s the interesting in-progress Ajax Push Engine

and in erlang there’s erlycomet (built on mochiweb)

so, ﬂash’s XMLSocket

Zeddius Zeddicus 8200 Browser Orbited 8100 it turns this

Zeddicus Browser 8200 into this

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

no lying needed

of course, it may be non-standard and might not work great across ﬁrewalls. but if you can use it, it’s pretty great

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

there are a few nice libraries for xml socket on github

tmm1 / jssocket my favorite is tmm1’s jssocket

defunkt / jssocket (i have a fork which removes the jquery dependencies)

ﬁnally: HTML5’s WebSocket

it’s still a proposed draft but it’ll let you open a socket to any serve that speaks the special WebSocket protocol

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

so, in review ?

comet

should be called asteroid

ﬂash’s XMLSocket

is non-standard but nice

HTML5’s WebSocket

not yet here but futuristic

you should give orbited a shot

with json

0 probably null terminated

Django Orbited 8000 don’t load orbited in django

Orbited 8100 use them alongside each other

is that it? ?

that’s it !

Thank You

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The Real-Time Web (and Other Buzzwords)

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