add Elixir source for tutorial 6

elixir/rpc_client.exs

@@ -0,0 +1,36 @@
+defmodule FibonacciRpcClient do
+  def wait_for_messages(_channel, correlation_id) do
+    receive do
+      {:basic_deliver, payload, %{correlation_id: ^correlation_id}} ->
+        {n, _} = Integer.parse(payload)
+        n
+    end
+  end
+  def call(n) do
+    {:ok, connection} = AMQP.Connection.open
+    {:ok, channel} = AMQP.Channel.open(connection)
+
+    {:ok, %{queue: queue_name}} = AMQP.Queue.declare(channel, "", exclusive: true)
+    AMQP.Basic.consume(channel, queue_name, nil, no_ack: true)
+    correlation_id = :erlang.unique_integer |> :erlang.integer_to_binary |> Base.encode64
+    request = to_string(n)
+    AMQP.Basic.publish(channel, "", "rpc_queue", request, reply_to: queue_name, correlation_id: correlation_id)
+
+    FibonacciRpcClient.wait_for_messages(channel, correlation_id)
+  end
+end
+
+num =
+  case System.argv do
+    []    -> 30
+    param ->
+      {x, _} =
+        param
+        |> Enum.join(" ")
+        |> Integer.parse
+      x
+  end
+
+IO.puts " [x] Requesting fib(#{num})"
+response = FibonacciRpcClient.call(num)
+IO.puts " [.] Got #{response}"

elixir/rpc_server.exs

@@ -0,0 +1,33 @@
+defmodule FibServer do
+  def fib(0), do: 0
+  def fib(1), do: 1
+  def fib(n) when n > 1, do: fib(n-1) + fib(n-2)
+
+  def wait_for_messages(channel) do
+    receive do
+      {:basic_deliver, payload, meta} ->
+        {n, _} = Integer.parse(payload)
+        IO.puts " [.] fib(#{n})"
+        response = fib(n)
+
+        AMQP.Basic.publish(channel, "", meta.reply_to, "#{response}", correlation_id: meta.correlation_id)
+        AMQP.Basic.ack(channel, meta.delivery_tag)
+
+        wait_for_messages(channel)
+    end
+  end
+end
+
+{:ok, connection} = AMQP.Connection.open
+{:ok, channel} = AMQP.Channel.open(connection)
+
+AMQP.Queue.declare(channel, "rpc_queue")
+
+AMQP.Basic.qos(channel, prefetch_count: 1)
+
+AMQP.Basic.consume(channel, "rpc_queue")
+
+IO.puts " [x] Awaiting RPC requests"
+
+FibServer.wait_for_messages(channel)
+