implement retry & restart with exponential backoff to handle websocket disconnections (#64)

lib/algora/restream/websocket.ex

@@ -4,8 +4,17 @@ defmodule Algora.Restream.Websocket do
 
   alias Algora.{Accounts, Chat}
 
-  def start_link(%{url: url, video: video}) do
-    WebSockex.start_link(url, __MODULE__, %{url: url, video: video})
+  def start_link(%{url: url, video: video} = opts) do
+    retry = opts[:retry] || 0
+    restart = opts[:restart] || 0
+    Logger.info("Starting WebSocket: #{video.id} (restart: #{restart}, retry: #{retry})")
+
+    WebSockex.start_link(url, __MODULE__, %{
+      url: url,
+      video: video,
+      restart: restart,
+      retry: retry
+    })
   end
 
   def handle_frame({:text, msg}, state) do
@@ -23,9 +32,41 @@ defmodule Algora.Restream.Websocket do
     end
   end
 
-  def handle_disconnect(_reason, state) do
-    Logger.error("WebSocket disconnected: #{state.video.id}")
-    {:reconnect, state}
+  def handle_connect(_conn, state) do
+    if state.restart == 0 and state.retry == 0 do
+      Logger.info("WebSocket connected: #{state.video.id}")
+    else
+      Logger.info(
+        "WebSocket reconnected: #{state.video.id} (restart: #{state.restart}, retry: #{state.retry})"
+      )
+    end
+
+    {:ok, state}
+  end
+
+  def handle_disconnect(reason, state) do
+    Logger.error("WebSocket disconnected: #{state.video.id} (reason: #{inspect(reason)})")
+
+    # latest_video = Library.get_latest_video(Accounts.get_user!(state.video.user_id))
+    # socket_video = Library.get_video!(state.video.id)
+    # if socket_video.id == latest_video.id and socket_video.is_live and state.retry < 10 do
+
+    if state.retry < 3 do
+      :timer.sleep(:timer.seconds(min(2 ** state.retry, 60)))
+      state = %{state | retry: state.retry + 1}
+      {:reconnect, state}
+    else
+      :timer.sleep(:timer.seconds(min(2 ** state.restart, 60)))
+      state = %{state | restart: state.restart + 1, retry: 0}
+
+      Task.Supervisor.start_child(
+        Algora.TaskSupervisor,
+        fn -> Algora.Restream.Websocket.start_link(state) end,
+        restart: :transient
+      )
+
+      {:ok, state}
+    end
   end
 
   defp handle_payload(%{"eventPayload" => %{"contentModifiers" => %{"whisper" => true}}}, state) do