Automatic reconnect to server with exp backoff

frontend/src/app.ts

@@ -14,16 +14,21 @@ term.open(document.getElementById("terminal"));
 fitAddon.fit();
 window.addEventListener("resize", () => fitAddon.fit());
 
-const socket = new WebSocket(
+const initialRetryDelayMs = 200;
+let retryDelayMs = initialRetryDelayMs;
+
+function tryConnect() {
+  console.log("Connecting to server...");
+  socket = new WebSocket(
     (document.location.protocol === "http:" ? "ws://" : "wss://") +
       document.location.host +
       `/api/v1/ws?lang=${lang}`
-);
-
-socket.addEventListener("open", () =>
-  console.log("Successfully connected to server")
-);
-socket.addEventListener("message", (event) => {
+  );
+  socket.addEventListener("open", () => {
+    retryDelayMs = initialRetryDelayMs;
+    console.log("Successfully connected to server");
+  });
+  socket.addEventListener("message", (event: MessageEvent) => {
     let message: any;
     try {
       message = JSON.parse(event.data);
@@ -47,23 +52,35 @@ socket.addEventListener("message", (event) => {
           console.error("Unexpected message from server:", message);
           return;
         }
-      monaco.editor.setModelLanguage(editor.getModel(), message.monacoLanguage);
+        monaco.editor.setModelLanguage(
+          editor.getModel(),
+          message.monacoLanguage
+        );
         return;
       default:
         console.error("Unexpected message from server:", message);
         return;
     }
-});
-socket.addEventListener("close", (event) => {
+  });
+  socket.addEventListener("close", (event: CloseEvent) => {
     if (event.wasClean) {
       console.log("Connection closed cleanly");
     } else {
       console.error("Connection died");
     }
-});
-socket.addEventListener("onerror", (event) =>
-  console.error("Connection error:", event)
-);
+    scheduleConnect();
+  });
+}
+
+function scheduleConnect() {
+  const delay = retryDelayMs * Math.random();
+  console.log(`Trying to reconnect in ${Math.floor(delay)}ms`);
+  setTimeout(tryConnect, delay);
+  retryDelayMs *= 2;
+}
+
+let socket = null;
+tryConnect();
 
 term.onData((data) =>
   socket.send(JSON.stringify({ event: "terminalInput", input: data }))