em-zeromq

This gem is currently maintained by schmurfy, it will stay here for now but may be moved to my account later.

EventMachine support for ZeroMQ

Supported on:

• MRI 1.9+
• Rubinius
• JRuby

While the gem should work on Rubinius and JRuby I mainly use it with MRI 1.9+ so there may be some glitchs.

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To ensure your zeromq context won't be reclaimed by the garbage collector you need to keep a reference to it in scope, this is what you don't want to do (that's how the example used to be written):

EM.run do
  context = EM::ZeroMQ::Context.new(1)
  dealer_socket = context.socket(...)
  dealer_socket.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 may be true for references to socket but I have no evidence of that.
It should not be a major problem anyway since code like above is only written for examples/tests but I just pulled my hair trying to figure out why my test code was not working so now you have been warned !

Until the gem hit the 1.0 mark you should not use the "~>" operator in your Gemfile, lock yourself to the exact version you want. That said I will use the second digit to flag api changes but be aware that small changes can still occur between releases.

require 'em-zeromq'

zmq = EM::ZeroMQ::Context.new(1)

EM.run {
  push = zmq.socket(ZMQ::PUSH)
  push.connect("tcp://127.0.0.1:2091")

  pull = zmq.socket(ZMQ::PULL)
  pull.bind("tcp://127.0.0.1:2091")

  pull.on(:message) { |part|
    puts part.copy_out_string
    part.close
  }

  EM.add_periodic_timer(1) {
    push.send_msg("Hello")
  }
}

Note that it's important to close message parts to avoid memory leaks.

(The MIT License)

Copyright (c) 2011 - 2012

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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