EZMQ (Effortless ZeroMQ)

Overview

EZMQ is a wrapper around the wonderful ffi-rzmq gem, which (as the name suggests) uses FFI, and exposes a fairly raw C-like interface. As elegant as 0MQ is, C doesn't feel like Ruby, and FFI bindings feel like C. EZMQ makes some reasonable assumptions to help you focus on what makes your code special, and not worry about setting up 0MQ.

Any of the magical hand-wavey bits (contexts, sockets, etc) are still exposed for tinkering, EZMQ just starts you off with some sane defaults.

Examples

Most of these examples are trivial, because ZMQ is just the fabric of your networked application(s).

Echo Server

Waits for a request, replies with the same request.

require 'ezmq'

server = EZMQ::Server.new
server.listen do |message|
  message
end

Synchronous Client Request

Sends a message, prints the reply when it arrives.

require 'ezmq'

client = EZMQ::Client.new
puts client.request 'test'

Confirming Logging Server

Waits for a request, prints it to STDOUT, and thanks the client for it.

require 'ezmq'

server = EZMQ::Server.new
server.listen do |message|
  puts message
  'Thanks for the message!' # The return of the block is sent to the client.
end

JSON Echo Server

Waits for JSON message, decodes it, re-encodes it, and sends it back.

require 'ezmq'
require 'json'

server = EZMQ::Server.new encode: -> m { JSON.dump m }, decode: -> m { JSON.load m }
server.listen do |message|
  message
end

JSON Synchronous Client Request

Encodes a message in JSON, sends it twice, prints the first one raw, and decodes the second.

require 'ezmq'
require 'json'

client = EZMQ::Client.new encode: -> m { JSON.dump m }
puts client.request 'test'
client.decode = -> m { JSON.load m }
puts client.request 'test'

'foorever' Publisher

Publishes an endless stream of 'foo's with a topic of 'foorever'.

require 'ezmq'

publisher = EZMQ.Publisher.new

loop do
  publisher.send 'foo', topic: 'foorever'
end

'foorever' Subscriber

Subscribes to topic 'foorever', prints any messages it receives.

require 'ezmq'

subscriber = EZMQ.Subscriber.new topic: 'foorever'
subscriber.listen do |message, topic|
  puts "[#{ topic }] #{ message }"
end

Pipeline Work Generator

Generates work, distributes it to workers via PUSH socket.

require 'ezmq'
require 'json'

generator = EZMQ::Pusher.new :bind, encode: -> m { JSON.dump m }

15.times do |id|
  work = { 'id' => "task_#{ id }", 'request' => '100' }
  puts "Generated work #{work}"
  generator.send work
end

Pipeline Workers

3 worker threads PULL work from the Generator and PUSH results to the Collector.

The 'work' here is generating a random number between 1 and a requested maximum.

require 'ezmq'
require 'json'

workers = []

3.times do |id|
  workers << Thread.new do
    input = EZMQ::Puller.new :connect, decode: -> m { JSON.load m }
    output = EZMQ::Pusher.new port: 5556, encode: -> m { JSON.dump m }
    input.listen do |work|
      puts "Worker #{id} pulled #{work}"
      result = rand(1..work['request'].to_i)
      report = { 'id' => work['id'], 'result' => result }
      output.send report
    end
  end
end

workers.each(&:join)

Pipeline Results Collector

PULLs results from workers and prints it to STDOUT.

require 'ezmq'
require 'json'

collector = EZMQ::Puller.new port: 5556
collector.listen do |message|
  puts message
end

Operating System Notes

As this relies on ffi-rzmq, you will need to have the zeromq libraries available.

For OSX, Homebrew is probably the easiest way to handle this:

brew install zeromq

For Ubuntu, Chris Lea's PPA is a good choice:

sudo add-apt-repository ppa:chris-lea/zeromq
sudo aptitude update
sudo aptitude install libzmq3-dev

For Windows, you should really consult the ØMQ documentation.