Ruby: RPC examples.

ruby/rpc_client.rb

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+#!/usr/bin/env ruby
+# encoding: utf-8
+
+# Note: This is just proof of concept. For
+# real-world usage, you are strongly advised
+# to use https://github.com/ruby-amqp/rpc
+# or some other RPC library.
+
+require "amqp"
+
+class FibonacciRpcClient
+  def initialize
+    subscribe_to_callback_queue
+  end
+
+  def connection
+    @connection ||= AMQP.connect(:host => "localhost")
+  end
+
+  def channel
+    @channel ||= AMQP::Channel.new(self.connection)
+  end
+
+  def callback_queue
+    @callback_queue ||= self.channel.queue("", :exclusive => true)
+  end
+
+  def requests
+    @requests ||= Hash.new
+  end
+
+  def call(n, &block)
+    corr_id = rand(10_000_000).to_s
+    self.requests[corr_id] = nil
+    self.callback_queue.append_callback(:declare) do
+      AMQP::Exchange.default.publish(n.to_s, :routing_key => "rpc_queue", :reply_to => self.callback_queue.name, :correlation_id => corr_id)
+
+      EM.add_periodic_timer(0.1) do
+        # p self.requests
+        if result = self.requests[corr_id]
+          block.call(result.to_i)
+          EM.stop
+        end
+      end
+    end
+  end
+
+  private
+  def subscribe_to_callback_queue
+    self.callback_queue.subscribe do |header, body|
+      corr_id = header.correlation_id
+      unless self.requests[corr_id]
+        self.requests[corr_id] = body
+      end
+    end
+  end
+end
+
+EM.run do
+  fibonacci_rpc = FibonacciRpcClient.new()
+
+  puts " [x] Requesting fib(30)"
+  fibonacci_rpc.call(30) do |response|
+    puts " [.] Got #{response}"
+  end
+end

ruby/rpc_server.rb

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+#!/usr/bin/env ruby
+# encoding: utf-8
+
+require "amqp"
+
+def fib(n)
+  return n if n == 0 || n == 1
+  return fib(n - 1) + fib(n - 2)
+end
+
+AMQP.start(:host => "localhost") do |connection|
+  channel = AMQP::Channel.new(connection)
+  queue   = channel.queue("rpc_queue")
+
+  channel.prefetch(1)
+
+  queue.subscribe(:ack => true) do |header, body|
+    n = body.to_i
+
+    puts " [.] fib(#{n})"
+    response = fib(n)
+
+    AMQP::Exchange.default.publish(response.to_s, :routing_key => header.reply_to, :correlation_id => header.correlation_id)
+    header.ack
+  end
+
+  puts " [x] Awaiting RPC requests"
+end