bunny_rpc_fib_client.rb

#!/usr/bin/env ruby
require 'bunny'
require 'securerandom'

conn = Bunny.new
conn.start

class FibonacciClient
  def initialize(conn, server_queue)
    ch              = conn.create_channel
    @x              = ch.default_exchange
    @reply_queue    = ch.queue("", :exclusive => true)
    @server_queue   = server_queue

    @results = Hash.new { |h,k| h[k] = Queue.new }
    @reply_queue.subscribe(block: false) do |delivery_info, properties, payload|
      @results[properties[:correlation_id]].push(payload.to_i)
    end
  end

  def call(n)
    correlation_id = SecureRandom.uuid

    @x.publish(n.to_s,
               :routing_key    => @server_queue,
               :correlation_id => correlation_id,
               :reply_to       => @reply_queue.name)

    result = @results[correlation_id].pop
    @results.delete correlation_id # to prevent memory leak
    result
  end
end

client   = FibonacciClient.new(conn, "rpc_queue")
puts " [x] Requesting fib(30)"
response = client.call(30)
puts " [.] Got #{response}"

conn.close