EM-PosixMQ

EM-PosixMQ integrates posix_mq Ruby library into EventMachine, allowing asynchronous reading from a POSIX message queue.

For detailed information about the usage of POSIX message queues check the manpages of POSIX message queues and documentation of the Ruby bindings.

Server (reads from a POSIX message queue):

require "em-posixmq"

class MyPosixMQ < EM::PosixMQ::Watcher
  def receive_message(message, priority)
    puts "received message with priority #{priority}: #{message.inspect}"
  end
end

EM.run do
  posix_mq = POSIX_MQ.new "/my_posix_mq", IO::CREAT | IO::RDONLY | IO::NONBLOCK
  EM::PosixMQ.run posix_mq, MyPosixMQ
end

Client (writes into a POSIX message queue):

require "posix_mq"
require "securerandom"

posix_mq = POSIX_MQ.new "/my_posix_mq", IO::CREAT | IO::WRONLY | IO::NONBLOCK

while true do
  message = SecureRandom.hex 6
  priority = SecureRandom.random_number 9
  
  puts "sending message '#{message}' with priority #{priority} to the queue..."
  posix_mq.send message, priority
  
  sleep SecureRandom.random_number
end

The client script will write random messages with random priority into a POSIX message queue named "/my_posix_mq" at variable intervals.

In order to use EM-PosixMQ a class handler must be created. Such class must inherit from EM::PosixMQ::Watcher and define the method receive_message which would be called with parameters message (a String) and priority (a Fixnum) upon receipt of a message from the message queue.

class MyPosixMQ < EM::PosixMQ::Watcher
  def receive_message(message, priority)
    # do something with the message (and priority).
  end
end

EM::PosixMQ.run posix_mq, Handler

Attaches a POSIX_MQ instance to the EventMachine reactor for asynchronous reading. The method requires two parameters:

• posix_mq - Instance of POSIX_MQ class being managed by EventMachine. The instance must be opened with read access.
• Handler - The name of the class inheriting from EM::PosixMQ::Watcher and defining the method receive_message.

EM-PosixMQ is provided as a Ruby Gem:

~$ gem install em-posixmq

EM-PosixMQ depends on POSIX message queues which are implemented in Linux and BSD.

Many thanks to Eric Wong, the author of posix_mq Ruby library.