Cleanup work

.gitignore

@@ -33,6 +33,7 @@ birdy_chat-*.tar
 
 # Ignore messages folder
 /priv/messages/
+!priv/messages/README.md
 
 # In case you use Node.js/npm, you want to ignore these.
 npm-debug.log

config/runtime.exs

@@ -21,7 +21,7 @@ if System.get_env("PHX_SERVER") do
 end
 
 config :birdy_chat, BirdyChatWeb.Endpoint,
-  http: [port: String.to_integer(System.get_env("PORT", "4000"))]
+  http: [port: String.to_integer(System.get_env("BIRDY_CHAT_PORT", "4000"))]
 
 if config_env() == :prod do
   # The secret key base is used to sign/encrypt cookies and other secrets.

lib/birdy_chat/dispatcher.ex

@@ -1,4 +1,18 @@
 defmodule BirdyChat.Dispatcher do
+  @moduledoc """
+  Main dispatcher of messages - decides to either write them to local file system or send them via
+  HTTP to peers.
+
+  It originally started as a websocket connection between servers, but then I decided to rip
+  it out and replace with simple HTTP request-response for the following reasons:
+
+  1. HTTP guarantees immediate feedback (request succeeds or not), making the addition of caching
+  or retries easy.
+  2. HTTP requests have well-know semantic so I can i.e use HTTP statuses for error signals
+  instead of inventing my own error language.
+  """
+
+  @spec dispatch(Ecto.Changeset.t()) :: :ok | {:error, String.t()}
   def dispatch(%Ecto.Changeset{changes: changes} = changeset) do
     case changes do
       %{routing: :local} -> BirdyChat.MessageWriter.write(changeset.changes)
@@ -6,13 +20,13 @@ defmodule BirdyChat.Dispatcher do
     end
   end
 
-  def send_to_remote(%{server: server, to: to} = message) do
+  defp send_to_remote(%{server: server, from: from} = message) do
-    {_name, base_url} =
+    {name, base_url} =
       BirdyChat.Identity.peers()
       |> Enum.find(fn {name, _url} -> name == server end)
 
     api_url = base_url <> "/api/internal"
-    token = Phoenix.Token.sign(BirdyChatWeb.Endpoint, "serverAuth", to)
+    token = Phoenix.Token.sign(BirdyChatWeb.Endpoint, "serverAuth", from)
 
     {_request, result} =
       Req.new(url: api_url, retry: false, method: :post)
@@ -24,6 +38,12 @@ defmodule BirdyChat.Dispatcher do
     # Handle more when you encounter errors
     case result do
       %Req.Response{status: 201} -> :ok
+      # This should never happen under normal circumstances so I am commenting this out but maybe
+      # needs a second look.
+      # %Req.Response{status: 403} -> {:error, "Unauthorised"}
+
+      # Peer is down.
+      %Req.TransportError{reason: :econnrefused} -> {:error, "peer #{name} is unreachable"}
     end
   end
 

lib/birdy_chat/identity.ex

@@ -55,6 +55,12 @@ defmodule BirdyChat.Identity do
           peers: %{"test2" => "http://localhost:4001"},
           mode: :test
         }
+
+      {identity, peers} ->
+        peers = parse_peers(peers)
+        identity = parse_identity(identity)
+
+        %__MODULE__{identity: identity, peers: peers, mode: :connected}
     end
   end
 end

lib/birdy_chat/message_writer.ex

@@ -1,5 +1,7 @@
 defmodule BirdyChat.MessageWriter do
-  @moduledoc false
+  @moduledoc """
+  Simple file writer that stores messages in priv folder of Elixir application/release.
+  """
 
   @spec write(%{to: String.t(), from: String.t(), message: String.t()}) :: :ok
   def write(message) do

lib/birdy_chat_web/api/messages/controller.ex

@@ -10,10 +10,10 @@ defmodule BirdyChatWeb.Api.Messages.Controller do
             |> put_status(:created)
             |> render(:create, message: changeset.changes)
 
-          :error ->
+          {:error, error} ->
             conn
             |> put_status(:unprocessable_entity)
-            |> render(:error, changeset: changeset)
+            |> render(:error, message: error)
         end
 
       {:error, changeset} ->

lib/birdy_chat_web/api/messages/json.ex

@@ -3,6 +3,10 @@ defmodule BirdyChatWeb.Api.Messages.JSON do
     message
   end
 
+  def render("error.json", %{message: message}) do
+    %{errors: %{"general" => Gettext.dgettext(BirdyChatWeb.Gettext, "errors", message, [])}}
+  end
+
   def render("error.json", %{changeset: changeset}) do
     errors = Ecto.Changeset.traverse_errors(changeset, &get_error/1)
     %{errors: errors}

mix.exs

@@ -63,7 +63,10 @@ defmodule BirdyChat.MixProject do
       {:jason, "~> 1.2"},
       {:dns_cluster, "~> 0.2.0"},
       {:bandit, "~> 1.5"},
-      {:credo, "~> 1.0", only: [:dev, :test]},
+
+      # Static analysis tools
+      {:credo, "~> 1.0", only: [:dev, :test], runtime: false},
+      {:dialyxir, "~> 1.0", only: [:dev, :test], runtime: false},
 
       # Telemetry
       {:opentelemetry, "~> 1.0"},
@@ -90,6 +93,7 @@ defmodule BirdyChat.MixProject do
       precommit: [
         "compile --warnings-as-errors",
         "credo --strict",
+        "dialyzer",
         "deps.unlock --unused",
         "format",
         "test"

mix.lock

@@ -7,9 +7,11 @@
   "credo": {:hex, :credo, "1.7.16", "a9f1389d13d19c631cb123c77a813dbf16449a2aebf602f590defa08953309d4", [:mix], [{:bunt, "~> 0.2.1 or ~> 1.0", [hex: :bunt, repo: "hexpm", optional: false]}, {:file_system, "~> 0.2 or ~> 1.0", [hex: :file_system, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "d0562af33756b21f248f066a9119e3890722031b6d199f22e3cf95550e4f1579"},
   "ctx": {:hex, :ctx, "0.6.0", "8ff88b70e6400c4df90142e7f130625b82086077a45364a78d208ed3ed53c7fe", [:rebar3], [], "hexpm", "a14ed2d1b67723dbebbe423b28d7615eb0bdcba6ff28f2d1f1b0a7e1d4aa5fc2"},
   "decimal": {:hex, :decimal, "2.3.0", "3ad6255aa77b4a3c4f818171b12d237500e63525c2fd056699967a3e7ea20f62", [:mix], [], "hexpm", "a4d66355cb29cb47c3cf30e71329e58361cfcb37c34235ef3bf1d7bf3773aeac"},
+  "dialyxir": {:hex, :dialyxir, "1.4.7", "dda948fcee52962e4b6c5b4b16b2d8fa7d50d8645bbae8b8685c3f9ecb7f5f4d", [:mix], [{:erlex, ">= 0.2.8", [hex: :erlex, repo: "hexpm", optional: false]}], "hexpm", "b34527202e6eb8cee198efec110996c25c5898f43a4094df157f8d28f27d9efe"},
   "dns_cluster": {:hex, :dns_cluster, "0.2.0", "aa8eb46e3bd0326bd67b84790c561733b25c5ba2fe3c7e36f28e88f384ebcb33", [:mix], [], "hexpm", "ba6f1893411c69c01b9e8e8f772062535a4cf70f3f35bcc964a324078d8c8240"},
   "ecto": {:hex, :ecto, "3.13.5", "9d4a69700183f33bf97208294768e561f5c7f1ecf417e0fa1006e4a91713a834", [:mix], [{:decimal, "~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: true]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "df9efebf70cf94142739ba357499661ef5dbb559ef902b68ea1f3c1fabce36de"},
   "elixir_make": {:hex, :elixir_make, "0.9.0", "6484b3cd8c0cee58f09f05ecaf1a140a8c97670671a6a0e7ab4dc326c3109726", [:mix], [], "hexpm", "db23d4fd8b757462ad02f8aa73431a426fe6671c80b200d9710caf3d1dd0ffdb"},
+  "erlex": {:hex, :erlex, "0.2.8", "cd8116f20f3c0afe376d1e8d1f0ae2452337729f68be016ea544a72f767d9c12", [:mix], [], "hexpm", "9d66ff9fedf69e49dc3fd12831e12a8a37b76f8651dd21cd45fcf5561a8a7590"},
   "esbuild": {:hex, :esbuild, "0.10.0", "b0aa3388a1c23e727c5a3e7427c932d89ee791746b0081bbe56103e9ef3d291f", [:mix], [{:jason, "~> 1.4", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "468489cda427b974a7cc9f03ace55368a83e1a7be12fba7e30969af78e5f8c70"},
   "expo": {:hex, :expo, "1.1.1", "4202e1d2ca6e2b3b63e02f69cfe0a404f77702b041d02b58597c00992b601db5", [:mix], [], "hexpm", "5fb308b9cb359ae200b7e23d37c76978673aa1b06e2b3075d814ce12c5811640"},
   "file_system": {:hex, :file_system, "1.1.1", "31864f4685b0148f25bd3fbef2b1228457c0c89024ad67f7a81a3ffbc0bbad3a", [:mix], [], "hexpm", "7a15ff97dfe526aeefb090a7a9d3d03aa907e100e262a0f8f7746b78f8f87a5d"},

priv/messages/README.md

@@ -0,0 +1 @@
+This folder is used for storing messages local to this server. The contents are otherwise ignored.

test/birdy_chat_web/api/messages_test.exs

@@ -15,6 +15,16 @@ defmodule BirdyChatWeb.Api.MessagesTest do
   end
 
   describe "POST /api/messages to other server" do
+    test "returns error when the peer is down", %{conn: conn, url: url} do
+      message = %{from: "test1-user", to: "test2-user", message: "123"}
+      Req.Test.expect(BirdyChat.Dispatcher, &Req.Test.transport_error(&1, :econnrefused))
+
+      payload = Jason.encode!(message)
+      conn = post(conn, url, payload)
+      assert result = json_response(conn, :unprocessable_entity)
+      assert result == %{"errors" => %{"general" => "peer test2 is unreachable"}}
+    end
+
     test "returns error when a peer is unknown", %{conn: conn, url: url} do
       message = %{from: "test1-user", to: "fake-user", message: "123"}
 
@@ -50,7 +60,7 @@ defmodule BirdyChatWeb.Api.MessagesTest do
         {"authorization", token} =
           Enum.find(conn.req_headers, fn {key, _v} -> key == "authorization" end)
 
-        {:ok, "test2-user"} =
+        {:ok, "test1-user"} =
           Phoenix.Token.verify(BirdyChatWeb.Endpoint, "serverAuth", token, max_age: 1200)
 
         assert conn.body_params == expected_body_params