The document discusses Rack, a Ruby web server interface. Rack provides a standard interface between web servers and Ruby frameworks/applications. If a Ruby object has a "call" method that takes an environment hash and returns a status, headers, and response body array, it can be run by any Rack-compatible web server. This allows Ruby web applications to be run using many different servers without code changes. The document provides examples of Rack applications and integrating them with servers like Thin and Mongrel.

1. 8 minutes on
Rack
Dan Webb (dan@danwebb.net)

2. Web Framework

3. Web Server

4. Library

5. A Convention

6. If you have a
Ruby object...

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

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

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

10. and you've got
yourself a web
application

11. Fin

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

13. 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)

14. // 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

15. def call(env)

16. {
"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"
}

17. [200, { 'Content-Type' => 'text/plain' }, "Hello #{@name}!"]
Status Code

18. [200, { 'Content-Type' => 'text/plain' }, "Hello #{@name}!"]
HTTP Headers

19. [200, { 'Content-Type' => 'text/plain' }, "Hello #{@name}!"]
Response Body

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

21. 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

22. [200, {
'Content-Type' => 'audio/mp3',
'Content-Length' => file.length.to_s
}, file]

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

24. Why?

25. Common interface

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

27. Write once,
serve however...

28. Convienient way
to write
micro apps

29. Example:
Development
Server

31. 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' )
)

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

33. rack.rubyforge.org

34. danwebb.net

35. Questions?