8 minutes on
Rack
Dan Webb (dan@danwebb.net)

Web Framework

Web Server

Library

A Convention

If you have a
Ruby object...

that has a call method which
takes one argument...
app.call(env)

and that method returns an
array with 3 elements...
[200, { 'Content-Type' => 'text/plain' }, 'Hello World!']

then you can connect it to any
web server that supports Rack
require 'thin'
Rack::Handler::Thin.run(app, :Port => 4000)

and you've got
yourself a web
application

Fin

app = Proc.new do |env|
[200, { 'Content-Type' => 'text/plain' },
'Hello World!']
end
require 'rubygems'
require 'thin'
Rack::Handler::Thin.run(app, :Port => 4000)

class HelloWorld
def initialize(name)
@name = name
end
def call(env)
[200, { 'Content-Type' => 'text/plain' },
\"Hello #{@name}!\"]
end
end
require 'rubygems'
require 'rack'
Rack::Handler::Mongrel.run(HelloWorld.new(\"Dan\"),
:Port => 4000)

// Courtesy of Pratik Naik!
#include \"ruby.h\"
VALUE method_call(VALUE self, VALUE env) {
VALUE response = rb_ary_new();
VALUE headers = rb_hash_new();
rb_hash_aset(headers,
rb_str_new2(\"Content-Type\"), rb_str_new2(\"text/plain\"));
rb_ary_push(response, INT2NUM(200));
rb_ary_push(response, headers);
rb_ary_push(response, rb_str_new2(\"Hello World!\"));
return response;
}
void Init_rock() {
VALUE Rock = rb_define_class(\"Rock\", rb_cObject);
rb_define_method(Rock, \"call\", method_call, 1);
}
// run.rb
require 'rock'
require 'thin'
Rack::Handler::Thin.run Rock.new, :Port => 4000

def call(env)

{
\"SERVER_NAME\"=>\"localhost\",
\"HTTP_ACCEPT_ENCODING\"=>\"gzip,deflate\",
\"HTTP_USER_AGENT\"=>\"Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-
GB; rv:1.9.0.4) Gecko/2008102920 Firefox/3.0.4\",
\"PATH_INFO\"=>\"/\",
\"SCRIPT_NAME\"=>\"\",
\"SERVER_PROTOCOL\"=>\"HTTP/1.1\",
\"HTTP_ACCEPT_LANGUAGE\"=>\"en-gb,en;q=0.5\",
\"HTTP_HOST\"=>\"localhost:4000\",
\"REMOTE_ADDR\"=>\"127.0.0.1\",
\"HTTP_KEEP_ALIVE\"=>\"300\",
\"REQUEST_PATH\"=>\"/\",
\"SERVER_SOFTWARE\"=>\"thin 0.8.2 codename Double Margarita\",
\"HTTP_ACCEPT_CHARSET\"=>\"ISO-8859-1,utf-8;q=0.7,*;q=0.7\",
\"HTTP_VERSION\"=>\"HTTP/1.1\",
\"REQUEST_URI\"=>\"/\",
\"SERVER_PORT\"=>\"4000\",
\"QUERY_STRING\"=>\"\",
\"GATEWAY_INTERFACE\"=>\"CGI/1.2\",
\"HTTP_ACCEPT\"=>\"text/html,application/xhtml+xml,application/xml;q=0.9,
*/*;q=0.8\",
\"HTTP_CONNECTION\"=>\"keep-alive\",
\"REQUEST_METHOD\"=>\"GET\"
}

[200, { 'Content-Type' => 'text/plain' }, \"Hello #{@name}!\"]
Status Code

[200, { 'Content-Type' => 'text/plain' }, \"Hello #{@name}!\"]
HTTP Headers

[200, { 'Content-Type' => 'text/plain' }, \"Hello #{@name}!\"]
Response Body

Response body can be any
object that respond_to?(:each)
file = File.new('myfile.xml')
[200, { 'Content-Type' => 'application/xml' }, file]

class StreamingFile
def initialize(file)
@file = file
end
def length
File.size(@file)
end
def last_modified
File.mtime(@file).rfc822
end
def each
File.open(@file, \"rb\") do |file|
while part = file.read(8192)
yield part
end
File.delete(@file)
end
end

[200, {
'Content-Type' => 'audio/mp3',
'Content-Length' => file.length.to_s
}, file]

Duck typing!
• Streaming
• Clean up after response sent
• Complex responses
• Loads more...

Why?

Common interface

• Passenger
• Mongrel
• CGI
• SCGI
• FastCGI
• Thin
• Ebb
• Fuzed
• Webrick
• Litespeed

Write once,
serve however...

Convienient way
to write
micro apps

Example:
Development
Server

class StaticOrRedirect
def initialize(options={})
@redirect_base = options[:redirect_base]
root = options[:root] || Dir.pwd
@file_server = Rack::File.new(root)
end
def call(env)
path = env[\"PATH_INFO\"]
resp = @file_server.call(env)
if resp.first == 404
[302, {
'Content-Type' => 'text/plain',
'Location' => \"#{@redirect_base}#{env['PATH_INFO']}\"
}, 'Not here!']
else
resp
end
end
end
Rack::Handler::Thin.run(
StaticOrRedirect.new( :redirect_base => 'http://bbc.co.uk' )
)

There's more...
• The Rack Gem
• Middleware
• Rack and Passenger
• rackup

rack.rubyforge.org

danwebb.net

Questions?