# module Rack::Handler

Handlers connect web servers with `Rack`.

`Rack` includes Handlers for `Thin`, `WEBrick`, `FastCGI`, `CGI`, `SCGI` and LiteSpeed.

Handlers usually are activated by calling `MyHandler.run(myapp)`. A second optional hash can be passed to include server-specific configuration.

### Constants

SERVER_NAMES

### Public Class Methods

default() click to toggle source

    # File lib/rack/handler.rb, line 51
    def self.default
      # Guess.
      if ENV.include?("PHP_FCGI_CHILDREN")
        Rack::Handler::FastCGI
      elsif ENV.include?(REQUEST_METHOD)
        Rack::Handler::CGI
      elsif ENV.include?("RACK_HANDLER")
        self.get(ENV["RACK_HANDLER"])
      else
        pick SERVER_NAMES
      end
    end

get(server) click to toggle source

    # File lib/rack/handler.rb, line 13
    def self.get(server)
      return unless server
      server = server.to_s

      unless @handlers.include? server
        load_error = try_require('rack/handler', server)
      end

      if klass = @handlers[server]
        const_get(klass)
      else
        const_get(server, false)
      end

    rescue NameError => name_error
      raise load_error || name_error
    end

pick(server_names) click to toggle source

Select first available `Rack` handler given an `Array` of server names. Raises `LoadError` if no handler was found.

    > pick ['thin', 'webrick']
    => Rack::Handler::WEBrick

    # File lib/rack/handler.rb, line 36
    def self.pick(server_names)
      server_names = Array(server_names)
      server_names.each do |server_name|
        begin
          return get(server_name.to_s)
        rescue LoadError, NameError
        end
      end

      raise LoadError, "Couldn't find handler for: #{server_names.join(', ')}."
    end

register(server, klass) click to toggle source

    # File lib/rack/handler.rb, line 85
    def self.register(server, klass)
      @handlers ||= {}
      @handlers[server.to_s] = klass.to_s
    end

try_require(prefix, const_name) click to toggle source

Transforms server-name constants to their canonical form as filenames, then tries to require them but silences the LoadError if not found

Naming convention:

    Foo # => 'foo'
    FooBar # => 'foo_bar.rb'
    FooBAR # => 'foobar.rb'
    FOObar # => 'foobar.rb'
    FOOBAR # => 'foobar.rb'
    FooBarBaz # => 'foo_bar_baz.rb'

    # File lib/rack/handler.rb, line 75
    def self.try_require(prefix, const_name)
      file = const_name.gsub(/^[A-Z]+/) { |pre| pre.downcase }.
        gsub(/[A-Z]+[^A-Z]/, '_\&').downcase

      require(::File.join(prefix, file))
      nil
    rescue LoadError => error
      error
    end