Code for step 4

lib/elixir_popularity/application.ex

@@ -8,7 +8,11 @@ defmodule ElixirPopularity.Application do
   def start(_type, _args) do
     children = [
       :hackney_pool.child_spec(:hn_id_pool, timeout: 15000, max_connections: 100),
-      ElixirPopularity.Repo
+      ElixirPopularity.Repo,
+      %{
+        id: ElixirPopularity.RMQPublisher,
+        start: {ElixirPopularity.RMQPublisher, :start_link, []}
+      }
     ]
 
     # See https://hexdocs.pm/elixir/Supervisor.html

lib/rmq_publisher.ex

@@ -0,0 +1,59 @@
+defmodule ElixirPopularity.RMQPublisher do
+  @behaviour GenRMQ.Publisher
+
+  @rmq_uri "amqp://rabbitmq:rabbitmq@localhost:5672"
+  @hn_exchange "hn_analytics"
+  @hn_item_ids_queue "item_ids"
+  @hn_bulk_item_data_queue "bulk_item_data"
+  @publish_options [persistent: false]
+
+  def init do
+    create_rmq_resources()
+
+    [
+      uri: @rmq_uri,
+      exchange: @hn_exchange
+    ]
+  end
+
+  def start_link do
+    GenRMQ.Publisher.start_link(__MODULE__, name: __MODULE__)
+  end
+
+  def hn_id_queue_size do
+    GenRMQ.Publisher.message_count(__MODULE__, @hn_item_ids_queue)
+  end
+
+  def publish_hn_id(hn_id) do
+    GenRMQ.Publisher.publish(__MODULE__, hn_id, @hn_item_ids_queue, @publish_options)
+  end
+
+  def publish_hn_items(items) do
+    GenRMQ.Publisher.publish(__MODULE__, items, @hn_bulk_item_data_queue, @publish_options)
+  end
+
+  def item_id_queue_name, do: @hn_item_ids_queue
+
+  def bulk_item_data_queue_name, do: @hn_bulk_item_data_queue
+
+  defp create_rmq_resources do
+    # Setup RabbitMQ connection
+    {:ok, connection} = AMQP.Connection.open(@rmq_uri)
+    {:ok, channel} = AMQP.Channel.open(connection)
+
+    # Create exchange
+    AMQP.Exchange.declare(channel, @hn_exchange, :topic, durable: true)
+
+    # Create queues
+    AMQP.Queue.declare(channel, @hn_item_ids_queue, durable: true)
+    AMQP.Queue.declare(channel, @hn_bulk_item_data_queue, durable: true)
+
+    # Bind queues to exchange
+    AMQP.Queue.bind(channel, @hn_item_ids_queue, @hn_exchange, routing_key: @hn_item_ids_queue)
+    AMQP.Queue.bind(channel, @hn_bulk_item_data_queue, @hn_exchange, routing_key: @hn_bulk_item_data_queue)
+
+    # Close the channel as it is no longer needed
+    # GenRMQ will manage its own channel
+    AMQP.Channel.close(channel)
+  end
+end