class AMQP::Utilities::EventLoopHelper

A helper that starts EventMachine reactor the optimal way depending on what Web server (if any) you are running. It should not be considered a 100% safe, general purpose EventMachine reactor “on/off switch” but is very useful in Web applications and some stand-alone applications.

This helper was inspired by Qusion project by Dan DeLeo.

h2. Key methods

Public Class Methods

eventmachine_thread() click to toggle source
# File lib/amqp/utilities/event_loop_helper.rb, line 23
def self.eventmachine_thread
  @eventmachine_thread
end
reactor_running?() click to toggle source
# File lib/amqp/utilities/event_loop_helper.rb, line 27
def self.reactor_running?
  EventMachine.reactor_running?
end
run(&block) click to toggle source

A helper that detects what app server (if any) is running and starts EventMachine reactor in the most optimal way. For event-driven servers like Thin and Goliath, this means relying on them starting the reactor but delaying execution of a block you pass to {EventLoopHelper.run} until reactor is actually running.

For Unicorn, Passenger, Mongrel and other servers and standalone apps EventMachine is started in a separate thread.

@example Using EventLoopHelper.run to start EventMachine reactor the optimal way without blocking current thread

AMQP::Utilities::EventLoopHelper.run do
  # Sets up default connection, accessible via AMQP.connection, and opens a channel
  # accessible via AMQP.channel for convenience
  AMQP.start

  exchange          = AMQP.channel.fanout("amq.fanout")

  AMQP.channel.queue("", :auto_delete => true, :exclusive => true).bind(exchange)
  AMQP::channel.default_exchange.publish("Started!", :routing_key => AMQP::State.queue.name)
end

@return [Thread] A thread EventMachine event loop will be started in (there is no guarantee it is already running).

@note This method, unlike EventMachine.run, DOES NOT block current thread.

# File lib/amqp/utilities/event_loop_helper.rb, line 63
def self.run(&block)
  if reactor_running?
    EventMachine.run(&block)

    return
  end

  @eventmachine_thread  ||= begin
                              case self.server_type
                              when :thin, :goliath, :evented_mongrel then
                                EventMachine.next_tick { block.call }
                                Thread.current
                              when :unicorn, :passenger, :mongrel, :scgi, :webrick, nil then
                                t = Thread.new { EventMachine.run(&block) }
                                # give EventMachine reactor some time to start
                                sleep(0.25)

                                t
                              else
                                t = Thread.new { EventMachine.run(&block) }
                                # give EventMachine reactor some time to start
                                sleep(0.25)

                                t
                              end
                            end

  @eventmachine_thread
end
server_type() click to toggle source

Type of server (if any) that is running.

@see AMQP::Utilities::ServerType.detect

# File lib/amqp/utilities/event_loop_helper.rb, line 34
def self.server_type
  @server_type ||= ServerType.detect
end