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redis_pubsub_demo.rb
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# Author: Pieter Noordhuis
# Description: Simple demo to showcase Redis PubSub with EventMachine
#
# Update 7 Oct 2010:
# - This example does *not* appear to work with Chrome >=6.0. Apparently,
# the WebSocket protocol implementation in the cramp gem does not work
# well with Chrome's (newer) WebSocket implementation.
#
# Requirements:
# - rubygems: eventmachine, thin, cramp, sinatra, yajl-ruby
# - a browser with WebSocket support
#
# Usage:
# ruby redis_pubsub_demo.rb
#
 
require 'rubygems'
require 'eventmachine'
require 'stringio'
require 'sinatra/base'
require 'cramp/controller'
require 'yajl'
 
# Incomplete evented Redis implementation specifically made for
# the new PubSub features in Redis.
class EventedRedis < EM::Connection
def self.connect
host = (ENV['REDIS_HOST'] || 'localhost')
port = (ENV['REDIS_PORT'] || 6379).to_i
EM.connect host, port, self
end
 
def post_init
@blocks = {}
end
def subscribe(*channels, &blk)
channels.each { |c| @blocks[c.to_s] = blk }
call_command('subscribe', *channels)
end
def publish(channel, msg)
call_command('publish', channel, msg)
end
def unsubscribe
call_command('unsubscribe')
end
def receive_data(data)
buffer = StringIO.new(data)
begin
parts = read_response(buffer)
if parts.is_a?(Array)
ret = @blocks[parts[1]].call(parts)
close_connection if ret === false
end
end while !buffer.eof?
end
private
def read_response(buffer)
type = buffer.read(1)
case type
when ':'
buffer.gets.to_i
when '*'
size = buffer.gets.to_i
parts = size.times.map { read_object(buffer) }
else
raise "unsupported response type"
end
end
def read_object(data)
type = data.read(1)
case type
when ':' # integer
data.gets.to_i
when '$'
size = data.gets
str = data.read(size.to_i)
data.read(2) # crlf
str
else
raise "read for object of type #{type} not implemented"
end
end
# only support multi-bulk
def call_command(*args)
command = "*#{args.size}\r\n"
args.each { |a|
command << "$#{a.to_s.size}\r\n"
command << a.to_s
command << "\r\n"
}
send_data command
end
end
 
class ChatController < Cramp::Controller::Websocket
on_start :create_redis
on_finish :handle_leave, :destroy_redis
on_data :received_data
def create_redis
@pub = EventedRedis.connect
@sub = EventedRedis.connect
end
def destroy_redis
@pub.close_connection_after_writing
@sub.close_connection_after_writing
end
def received_data(data)
msg = parse_json(data)
case msg[:action]
when 'join'
handle_join(msg)
when 'message'
handle_message(msg)
else
# skip
end
end
def handle_join(msg)
@user = msg[:user]
subscribe
publish :action => 'control', :user => @user, :message => 'joined the chat room'
end
def handle_leave
publish :action => 'control', :user => @user, :message => 'left the chat room'
end
def handle_message(msg)
publish msg.merge(:user => @user)
end
private
def subscribe
@sub.subscribe('chat') do |type,channel,message|
render message
end
end
def publish(message)
@pub.publish('chat', encode_json(message))
end
def encode_json(obj)
Yajl::Encoder.encode(obj)
end
def parse_json(str)
Yajl::Parser.parse(str, :symbolize_keys => true)
end
end
 
class StaticController < Sinatra::Base
enable :inline_templates
get('/') { erb :main }
end
 
EventMachine.run {
Cramp::Controller::Websocket.backend = :thin
Rack::Handler::Thin.run ChatController, :Port => 8081
Rack::Handler::Thin.run StaticController, :Port => 8082
}
 
__END__
@@ main
<html>
<head>
<script src='http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js'></script>
<script src='http://jquery-json.googlecode.com/files/jquery.json-2.2.min.js'></script>
<script src='http://datejs.googlecode.com/svn/trunk/build/date.js'></script>
<script>
$(document).ready(function(){
if (typeof WebSocket != 'undefined') {
$('#ask').show();
} else {
$('#error').show();
}
// join on enter
$('#ask input').keydown(function(event) {
if (event.keyCode == 13) {
$('#ask a').click();
}
})
// join on click
$('#ask a').click(function() {
join($('#ask input').val());
$('#ask').hide();
$('#channel').show();
$('input#message').focus();
});
 
function join(name) {
var host = window.location.host.split(':')[0];
var ws = new WebSocket("ws://" + host + ":8081/websocket");
 
var container = $('div#msgs');
ws.onmessage = function(evt) {
var obj = $.evalJSON(evt.data);
if (typeof obj != 'object') return;
 
var action = obj['action'];
var struct = container.find('li.' + action + ':first');
if (struct.length < 1) {
console.log("Could not handle: " + evt.data);
return;
}
var msg = struct.clone();
msg.find('.time').text((new Date()).toString("HH:mm:ss"));
 
if (action == 'message') {
var matches;
if (matches = obj['message'].match(/^\s*[\/\\]me\s(.*)/)) {
msg.find('.user').text(obj['user'] + ' ' + matches[1]);
msg.find('.user').css('font-weight', 'bold');
} else {
msg.find('.user').text(obj['user']);
msg.find('.message').text(': ' + obj['message']);
}
} else if (action == 'control') {
msg.find('.user').text(obj['user']);
msg.find('.message').text(obj['message']);
msg.addClass('control');
}
if (obj['user'] == name) msg.find('.user').addClass('self');
container.find('ul').append(msg.show());
container.scrollTop(container.find('ul').innerHeight());
}
$('#channel form').submit(function(event) {
event.preventDefault();
var input = $(this).find(':input');
var msg = input.val();
ws.send($.toJSON({ action: 'message', message: msg }));
input.val('');
});
// send name when joining
ws.onopen = function() {
ws.send($.toJSON({ action: 'join', user: name }));
}
}
});
</script>
<style type="text/css" media="screen">
* {
font-family: Georgia;
}
a {
color: #000;
text-decoration: none;
}
a:hover {
text-decoration: underline;
}
div.bordered {
margin: 0 auto;
margin-top: 100px;
width: 600px;
padding: 20px;
text-align: center;
border: 10px solid #ddd;
-webkit-border-radius: 20px;
}
#error {
background-color: #BA0000;
color: #fff;
font-weight: bold;
}
#ask {
font-size: 20pt;
}
#ask input {
font-size: 20pt;
padding: 10px;
margin: 0 10px;
}
#ask span.join {
padding: 10px;
background-color: #ddd;
-webkit-border-radius: 10px;
}
#channel {
margin-top: 100px;
height: 480px;
position: relative;
}
#channel div#descr {
position: absolute;
left: -10px;
top: -190px;
font-size: 13px;
text-align: left;
line-height: 20px;
padding: 5px;
width: 630px;
}
div#msgs {
overflow-y: scroll;
height: 400px;
}
div#msgs ul {
list-style: none;
padding: 0;
margin: 0;
text-align: left;
}
div#msgs li {
line-height: 20px;
}
div#msgs li span.user {
color: #ff9900;
}
div#msgs li span.user.self {
color: #aa2211;
}
div#msgs li span.time {
float: right;
margin-right: 5px;
color: #aaa;
font-family: "Courier New";
font-size: 12px;
}
div#msgs li.control {
text-align: center;
}
div#msgs li.control span.message {
color: #aaa;
}
div#input {
text-align: left;
margin-top: 20px;
}
div#input #message {
width: 600px;
border: 5px solid #bbb;
-webkit-border-radius: 3px;
font-size: 30pt;
}
</style>
</head>
<body>
<a href="http://gist.github.com/348262">
<img style="position: absolute; top: 0; right: 0; border: 0;" src="http://s3.amazonaws.com/github/ribbons/forkme_right_darkblue_121621.png" alt="Fork me on GitHub" />
</a>
<div id="error" class="bordered" style="display: none;">
This browser has no native WebSocket support.<br/>
Use a WebKit nightly or Google Chrome.
</div>
<div id="ask" class="bordered" style="display: none;">
Name: <input type="text" id="name" /> <a href="#"><span class="join">Join!</span></a>
</div>
<div id="channel" class="bordered" style="display: none;">
<div id="descr" class="bordered">
<strong>Note:</strong> your messages make a round-trip up and down the stack (including Redis)
before being displayed here.<br/>
<strong>Tip:</strong> open up another browser window
to see how quickly your messages are distributed.
</div>
<div id="msgs">
<ul>
<li class="message" style="display: none">
<span class="user"></span><span class="message"></span>
<span class="time"></span>
</li>
<li class="control" style="display: none">
<span class="user"></span>&nbsp;<span class="message"></span>
<span class="time"></span>
</li>
</ul>
</div>
<div id="input">
<form><input type="text" id="message" /></form>
</div>
</div>
</body>
</html>

Zeokat time to learn a few ruby, thanks.

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