add Elixir source for tutorial 5

elixir/emit_log_topic.exs

@@ -0,0 +1,17 @@
+{:ok, connection} = AMQP.Connection.open
+{:ok, channel} = AMQP.Channel.open(connection)
+
+{topic, message} = 
+  System.argv
+  |> case do
+    []            -> {"anonymous.info", "Hello World!"}
+    [message]     -> {"anonymous.info", message}
+    [topic|words] -> {topic, Enum.join(words, " ")}
+  end
+
+AMQP.Exchange.declare(channel, "topic_logs", :topic)
+
+AMQP.Basic.publish(channel, "topic_logs", topic, message)
+IO.puts " [x] Sent '[#{topic}] #{message}'"
+
+AMQP.Connection.close(connection)

elixir/receive_logs_topic.exs

@@ -0,0 +1,31 @@
+defmodule ReceiveLogsTopic do
+  def wait_for_messages(channel) do
+    receive do
+      {:basic_deliver, payload, meta} ->
+        IO.puts " [x] Received [#{meta.routing_key}] #{payload}"
+
+        wait_for_messages(channel)
+    end
+  end
+end
+
+{:ok, connection} = AMQP.Connection.open
+{:ok, channel} = AMQP.Channel.open(connection)
+
+AMQP.Exchange.declare(channel, "topic_logs", :topic)
+
+{:ok, %{queue: queue_name}} = AMQP.Queue.declare(channel, "", exclusive: true)
+
+if length(System.argv) == 0 do
+  IO.puts "Usage: mix run receive_logs_topic.exs [binding_key]..."
+  System.halt(1)
+end
+for binding_key <- System.argv do
+  AMQP.Queue.bind(channel, queue_name, "topic_logs", routing_key: binding_key)
+end
+
+AMQP.Basic.consume(channel, queue_name, nil, no_ack: true)
+
+IO.puts " [*] Waiting for messages. To exist press CTRL+C, CTRL+C"
+
+ReceiveLogsTopic.wait_for_messages(channel)