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Diffstat (limited to 'guides/source/initialization.textile')
| -rw-r--r-- | guides/source/initialization.textile | 108 |
1 files changed, 75 insertions, 33 deletions
diff --git a/guides/source/initialization.textile b/guides/source/initialization.textile index 155a439e64..12b2eb7458 100644 --- a/guides/source/initialization.textile +++ b/guides/source/initialization.textile @@ -1,13 +1,15 @@ h2. The Rails Initialization Process -This guide explains the internals of the initialization process in Rails as of Rails 3.1. It is an extremely in-depth guide and recommended for advanced Rails developers. +This guide explains the internals of the initialization process in Rails +as of Rails 4. It is an extremely in-depth guide and recommended for advanced Rails developers. * Using +rails server+ * Using Passenger endprologue. -This guide goes through every single file, class and method call that is required to boot up the Ruby on Rails stack for a default Rails 3.1 application, explaining each part in detail along the way. For this guide, we will be focusing on how the two most common methods (+rails server+ and Passenger) boot a Rails application. +This guide goes through every single file, class and method call that is +required to boot up the Ruby on Rails stack for a default Rails 4 application, explaining each part in detail along the way. For this guide, we will be focusing on how the two most common methods (+rails server+ and Passenger) boot a Rails application. NOTE: Paths in this guide are relative to Rails or a Rails application unless otherwise specified. @@ -22,16 +24,15 @@ The actual +rails+ command is kept in _bin/rails_: <ruby> #!/usr/bin/env ruby -begin - require "rails/cli" -rescue LoadError - railties_path = File.expand_path('../../railties/lib', __FILE__) +if File.exists?(File.join(File.expand_path('../../..', __FILE__), '.git')) + railties_path = File.expand_path('../../lib', __FILE__) $:.unshift(railties_path) - require "rails/cli" end +require "rails/cli" </ruby> -This file will attempt to load +rails/cli+. If it cannot find it then +railties/lib+ is added to the load path (+$:+) before retrying. +This file will first attempt to push the +railties/lib+ directory if +present, and then require +rails/cli+. h4. +railties/lib/rails/cli.rb+ @@ -46,7 +47,7 @@ require 'rails/script_rails_loader' Rails::ScriptRailsLoader.exec_script_rails! require 'rails/ruby_version_check' -Signal.trap("INT") { puts; exit } +Signal.trap("INT") { puts; exit(1) } if ARGV.first == 'plugin' ARGV.shift @@ -56,7 +57,7 @@ else end </ruby> -The +rbconfig+ file from the Ruby standard library provides us with the +RbConfig+ class which contains detailed information about the Ruby environment, including how Ruby was compiled. We can see this in use in +railties/lib/rails/script_rails_loader+. +The +rbconfig+ file from the Ruby standard library provides us with the +RbConfig+ class which contains detailed information about the Ruby environment, including how Ruby was compiled. We can see thisin use in +railties/lib/rails/script_rails_loader+. <ruby> require 'pathname' @@ -120,6 +121,9 @@ exec RUBY, SCRIPT_RAILS, *ARGV if in_rails_application? This is effectively the same as running +ruby script/rails [arguments]+, where +[arguments]+ at this point in time is simply "server". +TIP: If you execute +script/rails+ directly from your Rails app you will +avoid executing the code that we just described. + h4. +script/rails+ This file is as follows: @@ -134,23 +138,23 @@ The +APP_PATH+ constant will be used later in +rails/commands+. The +config/boot h4. +config/boot.rb+ -+config/boot.rb+ contains this: ++config/boot.rb+ contains: <ruby> # Set up gems listed in the Gemfile. -gemfile = File.expand_path('../../Gemfile', __FILE__) -begin - ENV['BUNDLE_GEMFILE'] = gemfile - require 'bundler' - Bundler.setup -rescue Bundler::GemNotFound => e - STDERR.puts e.message - STDERR.puts "Try running `bundle install`." - exit! -end if File.exist?(gemfile) +ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../../Gemfile', __FILE__) + +require 'bundler/setup' if File.exists?(ENV['BUNDLE_GEMFILE']) </ruby> -In a standard Rails application, there's a +Gemfile+ which declares all dependencies of the application. +config/boot.rb+ sets +ENV["BUNDLE_GEMFILE"]+ to the location of this file, then requires Bundler and calls +Bundler.setup+ which adds the dependencies of the application (including all the Rails parts) to the load path, making them available for the application to load. The gems that a Rails 3.1 application depends on are as follows: +In a standard Rails application, there's a +Gemfile+ which declares all +dependencies of the application. +config/boot.rb+ sets ++ENV['BUNDLE_GEMFILE']+ to the location of this file. If the Gemfile +exists, +bundler/setup+ is then required. + +The gems that a Rails 4 application depends on are as follows: + +TODO: change these when the Rails 4 release is near. * abstract (1.0.0) * actionmailer (3.1.0.beta) @@ -183,6 +187,8 @@ h4. +rails/commands.rb+ Once +config/boot.rb+ has finished, the next file that is required is +rails/commands+ which will execute a command based on the arguments passed in. In this case, the +ARGV+ array simply contains +server+ which is extracted into the +command+ variable using these lines: <ruby> +ARGV << '--help' if ARGV.empty? + aliases = { "g" => "generate", "c" => "console", @@ -195,6 +201,9 @@ command = ARGV.shift command = aliases[command] || command </ruby> +TIP: As you can see, an empty ARGV list will make Rails show the help +snippet. + If we used <tt>s</tt> rather than +server+, Rails will use the +aliases+ defined in the file and match them to their respective commands. With the +server+ command, Rails will run this code: <ruby> @@ -361,8 +370,9 @@ This method is defined like this: <ruby> def start + url = "#{options[:SSLEnable] ? 'https' : 'http'}://#{options[:Host]}:#{options[:Port]}" puts "=> Booting #{ActiveSupport::Inflector.demodulize(server)}" - puts "=> Rails #{Rails.version} application starting in #{Rails.env} on http://#{options[:Host]}:#{options[:Port]}" + puts "=> Rails #{Rails.version} application starting in #{Rails.env} on #{url}" puts "=> Call with -d to detach" unless options[:daemonize] trap(:INT) { exit } puts "=> Ctrl-C to shutdown server" unless options[:daemonize] @@ -372,6 +382,15 @@ def start FileUtils.mkdir_p(Rails.root.join('tmp', dir_to_make)) end + unless options[:daemonize] + wrapped_app # touch the app so the logger is set up + + console = ActiveSupport::Logger.new($stdout) + console.formatter = Rails.logger.formatter + + Rails.logger.extend(ActiveSupport::Logger.broadcast(console)) + end + super ensure # The '-h' option calls exit before @options is set. @@ -380,10 +399,18 @@ ensure end </ruby> -This is where the first output of the Rails initialization happens. This method creates a trap for +INT+ signals, so if you +CTRL+C+ the server, it will exit the process. As we can see from the code here, it will create the +tmp/cache+, +tmp/pids+, +tmp/sessions+ and +tmp/sockets+ directories if they don't already exist prior to calling +super+. The +super+ method will call +Rack::Server.start+ which begins its definition like this: +This is where the first output of the Rails initialization happens. This +method creates a trap for +INT+ signals, so if you +CTRL-C+ the server, +it will exit the process. As we can see from the code here, it will +create the +tmp/cache+, +tmp/pids+, +tmp/sessions+ and +tmp/sockets+ +directories. It then calls +wrapped_app+ which is responsible for +creating the Rack app, before creating and assignig an +instance of +ActiveSupport::Logger+. + +The +super+ method will call +Rack::Server.start+ which begins its definition like this: <ruby> -def start +def start &blk if options[:warn] $-w = true end @@ -403,22 +430,37 @@ def start pp wrapped_app pp app end -end -</ruby> -In a Rails application, these options are not set at all and therefore aren't used at all. The first line of code that's executed in this method is a call to this method: + check_pid! if options[:pid] -<ruby> -wrapped_app + # Touch the wrapped app, so that the config.ru is loaded before + # daemonization (i.e. before chdir, etc). + wrapped_app + + daemonize_app if options[:daemonize] + + write_pid if options[:pid] + + trap(:INT) do + if server.respond_to?(:shutdown) + server.shutdown + else + exit + end + end + + server.run wrapped_app, options, &blk +end </ruby> -This method calls another method: +The interesting part for a Rails app is the last line, +server.run+. Here we encounter the +wrapped_app+ method again, which this time +we're going to explore more. <ruby> @wrapped_app ||= build_app app </ruby> -Then the +app+ method here is defined like so: +The +app+ method here is defined like so: <ruby> def app @@ -440,7 +482,7 @@ The +options[:config]+ value defaults to +config.ru+ which contains this: # This file is used by Rack-based servers to start the application. require ::File.expand_path('../config/environment', __FILE__) -run YourApp::Application +run <%= app_const %> </ruby> |