README.md

@@ -29,18 +29,8 @@ curl -X POST http://localhost:4000/api/messages -H "Content-Type: application/js
 curl -X POST http://localhost:4001/api/messages -H "Content-Type: application/json" -d '{"from": "2-nibbler", "to": "1-bender", "message": "I am Nibbler, agent of the Nibblonian fleet."}'
 ```
 
-### Notes on queueing failed messages
-When messages fail to be delivered they are queued for retry at 30 second interval with a maximum of 5 retries by default (can be configured)
-
 ## Security
 This application uses a shared auth key (`AUTH_KEY`) to authenticate requests between servers. The key is provided as an environment variable and must be the same on all servers.
 
-## Next steps
-
-### Security - HTTPS with client certificates
+### Next steps
 HTTPS with client certificates should be implemented to ensure secure communication between servers and prevent unauthorized access and possible man-in-the-middle attacks.
-
-### Testing
-Full suite of unit tests should be implemented to ensure the correctness of the application's logic and behavior.
-
-### Finish implementation of Message Queue to queue failed messages for retry

lib/message_server/application.ex

@@ -14,7 +14,6 @@ defmodule MessageServer.Application do
     children = [
       {MessageServer.ServerRegistry, {server_id, servers}},
       {MessageServer.Storage, {server_id}},
-      {MessageServer.MessageQueue, [retry_interval: 30_000]},
       {Bandit, plug: MessageServer.Router, port: port}
     ]
 

lib/message_server/message_queue.ex

@@ -1,106 +0,0 @@
-defmodule MessageServer.MessageQueue do
-  use GenServer
-  require Logger
-  alias MessageServer.RemoteClient
-
-  @type queued_message :: %{
-          target_server: String.t(),
-          payload: map(),
-          timestamp: DateTime.t(),
-          retry_count: non_neg_integer()
-        }
-
-  @spec start_link(keyword()) :: GenServer.on_start()
-  def start_link(opts \\ []) do
-    {retry_interval, opts} = Keyword.pop(opts, :retry_interval, 30_000)
-    {queue_name, _opts} = Keyword.pop(opts, :name, __MODULE__)
-    GenServer.start_link(__MODULE__, retry_interval, name: queue_name)
-  end
-
-  @spec queue_message(String.t(), map()) :: :ok
-  def queue_message(target_server, payload) do
-    GenServer.cast(__MODULE__, {:queue_message, target_server, payload})
-  end
-
-  @spec process_queue() :: :ok
-  def process_queue do
-    GenServer.cast(__MODULE__, :process_queue)
-  end
-
-  @impl true
-  def init(retry_interval) do
-    :timer.send_interval(retry_interval, :process_queue)
-    {:ok, %{queue: [], processing: false}}
-  end
-
-  @impl true
-  def handle_cast({:queue_message, target_server, payload}, %{queue: queue} = state) do
-    message = %{
-      target_server: target_server,
-      payload: payload,
-      timestamp: DateTime.utc_now(),
-      retry_count: 0
-    }
-
-    Logger.info("Queueing message for offline server #{target_server}")
-    {:noreply, %{state | queue: [message | queue]}}
-  end
-
-  @impl true
-  def handle_cast(:process_queue, %{processing: true} = state) do
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_cast(:process_queue, %{queue: []} = state) do
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_cast(:process_queue, %{queue: queue} = state) do
-    {:noreply, %{state | processing: true}}
-
-    Task.start(fn ->
-      process_queued_messages(queue)
-      GenServer.cast(__MODULE__, {:processing_complete, []})
-    end)
-
-    {:noreply, state}
-  end
-
-  @impl true
-  def handle_cast({:processing_complete, failed_messages}, state) do
-    {:noreply, %{state | queue: failed_messages, processing: false}}
-  end
-
-  @impl true
-  def handle_info(:process_queue, state) do
-    handle_cast(:process_queue, state)
-  end
-
-  @spec process_queued_messages([queued_message()]) :: [queued_message()]
-  defp process_queued_messages(messages) do
-    Enum.reduce(messages, [], fn message, failed_acc ->
-      case attempt_delivery(message) do
-        :ok ->
-          Logger.info("Successfully delivered queued message to #{message.target_server}")
-          failed_acc
-
-        {:error, _reason} ->
-          updated_message = %{message | retry_count: message.retry_count + 1}
-
-          if updated_message.retry_count < 5 do
-            [updated_message | failed_acc]
-          else
-            Logger.error("Dropping message to #{message.target_server} after 5 retries")
-            failed_acc
-          end
-      end
-    end)
-  end
-
-  @spec attempt_delivery(queued_message()) :: :ok | {:error, String.t()}
-  defp attempt_delivery(%{target_server: target_server, payload: payload}) do
-    RemoteClient.send_message_to_server(target_server, payload)
-  end
-end

lib/message_server/remote_client.ex

@@ -1,7 +1,7 @@
 defmodule MessageServer.RemoteClient do
   require Logger
 
-  alias MessageServer.{MessageRequest, ServerRegistry, Auth, MessageQueue}
+  alias MessageServer.{MessageRequest, ServerRegistry, Auth}
 
   @spec send_message_to_server(String.t(), MessageRequest.t()) :: :ok | {:error, String.t()}
   def send_message_to_server(target_server_id, payload) do
@@ -15,7 +15,6 @@ defmodule MessageServer.RemoteClient do
 
       {:error, reason} = error ->
         Logger.error("Failed to send message to server #{target_server_id}: #{reason}")
-        MessageQueue.queue_message(target_server_id, payload)
         error
     end
   end

lib/message_server/router.ex

@@ -60,6 +60,11 @@ defmodule MessageServer.Router do
           |> send_resp(400, Jason.encode!(%{error: reason}))
       end
     else
+      {:error, :auth_failure, reason} ->
+        conn
+        |> put_resp_content_type("application/json")
+        |> send_resp(401, Jason.encode!(%{error: "Unauthorized", message: reason}))
+
       {:error, reason} ->
         conn
         |> put_resp_content_type("application/json")