Comet: an Overview and a New Solution Called Jabbify

Comet Overview

Brian MoschelJupiter IT

Overview

Why Comet?

Comet Overvie

wJabbify How It

Works Demo Showcase

Why Comet?

• Web 2.0 Trends1. Time Spent on a Page

Why Comet?

• Web 2.0 Trends2. Half life of a Page’s Content

Why Comet?

• Demand for Comet is growing• Desktop apps moving to the web

• Chat• Real time updates• Don’t like to reload

• Ajax:2003::Comet:2009

Uses

• Multi user collaboration apps– Wiki– Presentation

• Communication– Chat

• Preventing stale data– Stock ticker– Social web updates

• Others?

Polling

Comet Long Polling

Server

Client

Server

Client

Are weThere yet? No

Are weThere yet? No

Are weThere yet? No

Wait for data

Polling vs. Comet

Wait for data

How Comet Works: Client Side• Long Poll

– How?• XHR, JSONP, or any transport, with connection held open

– Pro• It works cross browser

– Con• More overhead

• Forever Frame– How?

• Iframe• Multipart XHR

– Pro• Less overhead, quicker responses

– Con• Lack of error handling, not cross browser

Client Side Issues

• Cross Browser– Duh

• 2 Connection Limit– Use wildcard DNS– Xxx.mywebsite.com -> mywebsite.com

• Synchronous request s (for JSONP)– Long poll has to close to allow other requests to

process

How Comet Works: Server Side

• Simultaneous connections– Traditional servers can’t scale– A thread shared multiple connections

• Wake up when you’re ready to send data

How Comet Works: Server Side

• Python– Orbited– Cometd

• Java– Jetty

• Erlang– ErlyComet

• .NET– Lightstreamer

• Service– Jabbify

Server Side Issues

• Scaling– Every user = 1 connection

• Complexity– Threading– Learning Curve

What is Jabbify?

• Comet, simplified• No server• No setup• JavaScript API and GET requests

Why Jabbify?

Simple to use

Scale easily

Rapid setup

Simple to usesynchronized (_continuations) { for(Iterator<Map.Entry <String, ArrayList<Continuation>>> iter = _continuations.entrySet().iterator(); iter.hasNext();){ Map.Entry<String, ArrayList<Continuation>> entry = iter.next(); ArrayList<Continuation> continuations = entry.getValue(); for(Continuation c : continuations){ c.resume(); } }_continuations.clear();}

Jabbify.connect({name: this.username}, this.continue_to('after_connect'))after_connect: function(){ Jabbify.send('vote','submit', {result: this.result})}

vs

Scale easily

• Scaling comet >> Scaling traditional web applications

• Resource intensive• Jabbify is built to scale as usage grows

Rapid Setup<New id="cf" class="org.mortbay.jetty.plus.naming.Resource"> <Arg>jms/connectionFactory</Arg> <Arg> <New class="org.apache.activemq.ActiveMQConnectionFactory"> <Arg>failover:(tcp://localhost:61616)?initialReconnectDelay=20&amp;maxReconnectDelay=900</Arg> </New> </Arg></New>

<script language="javascript" type="text/javascript" src="jabbify.js"></script>

vs

Comet is complex• Client

– Transports (JSONP, Window.name, Flash, XHR, iframe)

• Server– Special server– Setup time– Learning curve

• Scaling– Resource consumption– Threading issues

Jabbify is simple• Client to Client Comet

– JavaScript API• Jabbify.send(“message”,”create”,{message: “hi there”});

• Server to Client Comet– GET requests

• https://jabbify.com/message_push?key=123&type=message...

How It Works

Demo

Take Home Points

Comet is coming

Jabbify = easy Comet

Showcase• Jabbify Simple Chat Client• Keyboard Demo• Chat.unwrongest.com