EventMachine support for ZeroMQ

Tested and functional with Rubinius, jRuby, and 1.9.2.

If using 1.9.2 you must gem install ffi before using.

MRI 1.8.7 does not work with libzmq.

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To ensure your zeromq context won't be reclaimed by the ruby garbage collector you need to keep a reference to it in scope, this is what you don't want to do:

EM.run do
  context = EM::ZeroMQ::Context.new(1)
  dealer_socket = context.connect(...)
  dealer_socket.send_msg('', "ping")
end

If you do this everything will appear to work fine at first but as soon as the garbage collector is triggered your context will get destroyed and your application will hang.

The same should be true for references to socket.
It should not be a major problem anyway since code like above is only written for examples but I just pulled my hair trying to figure out why my test code was not working so now you have been warned !

require 'rubygems'
require 'em-zeromq'
    
Thread.abort_on_exception = true

class EMTestPullHandler
  attr_reader :received
  def on_readable(socket, messages)
    messages.each do |m|
      puts m.copy_out_string
    end
  end
end


ctx = EM::ZeroMQ::Context.new(1)
EM.run do
  # setup push sockets
  push_socket1 = ctx.bind( ZMQ::PUSH, 'tcp://127.0.0.1:2091')
  push_socket2 = ctx.bind( ZMQ::PUSH, 'ipc:///tmp/a')
  push_socket3 = ctx.bind( ZMQ::PUSH, 'inproc://simple_test')
  
  # setup one pull sockets listening to both push sockets
  pull_socket = ctx.connect( ZMQ::PULL, 'tcp://127.0.0.1:2091', EMTestPullHandler.new)
  pull_socket.connect('ipc:///tmp/a')
  pull_socket.connect('inproc://simple_test')
  
  n = 0
  
  # push_socket.hwm = 40
  # puts push_socket.hwm
  # puts pull_socket.hwm
  
  EM::PeriodicTimer.new(0.1) do
    puts '.'
    push_socket1.send_msg("t#{n += 1}_")
    push_socket2.send_msg("i#{n += 1}_")
    push_socket3.send_msg("p#{n += 1}_")
  end
end

(The MIT License)

Copyright (c) 2011

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