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# frozen_string_literal: true
module Rack
# *Handlers* connect web servers with Rack.
#
# Rack includes Handlers for Thin, WEBrick, FastCGI, CGI, SCGI
# and LiteSpeed.
#
# Handlers usually are activated by calling <tt>MyHandler.run(myapp)</tt>.
# A second optional hash can be passed to include server-specific
# configuration.
module Handler
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
# Select first available Rack handler given an `Array` of server names.
# Raises `LoadError` if no handler was found.
#
# > pick ['puma', 'webrick']
# => Rack::Handler::WEBrick
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
RACK_HANDLER = 'RACK_HANDLER'
SERVER_NAMES = %w(puma falcon webrick).freeze
private_constant :SERVER_NAMES
def self.default
if rack_handler = ENV[RACK_HANDLER]
self.get(rack_handler)
else
pick SERVER_NAMES
end
end
# 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'
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
def self.register(server, klass)
@handlers ||= {}
@handlers[server.to_s] = klass.to_s
end
autoload :WEBrick, "rack/handler/webrick"
register 'webrick', 'Rack::Handler::WEBrick'
end
end
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