@mikkel-ol/tunnelmole/src/websocket/setup-auto-reconnect.ts

Tunnelmole, an open source ngrok alternative. Instant public URLs for any http/https based application. Available as a command line application or as an NPM dependency for your code. Stable and maintained. Good test coverage. Works behind firewalls

/*
 * Handle automatic reconnection if a custom subdomain is used. Use a delay with exponential backoff.
 */
import log from "../logging/log.js";
import { Options } from "../options.js";
import { connect } from "./connect.js";
import HostipWebSocket from "./host-ip-websocket";

let reconnectAttempts = 0;
let isReconnecting = false;
const maxReconnectDelay = 30000; // Maximum delay of 30 seconds
const baseReconnectDelay = 1000; // Start with 1 second

// Every 6 hours, reset reconnectAttempts. This should keep reconnections fast for long lived connections.
let resetConnnectionAttemptsInterval;
const resetTheConnectionAttemptsInterval = () => {
  resetConnnectionAttemptsInterval = setInterval(() => {
    reconnectAttempts = 0;
  }, 21600000);
};

const attemptReconnection = async (options: Options) => {
  if (isReconnecting) return;
  isReconnecting = true;

  reconnectAttempts++;
  const reconnectDelay = Math.min(
    baseReconnectDelay * Math.pow(2, reconnectAttempts - 1),
    maxReconnectDelay,
  );

  setTimeout(async () => {
    log("Got disconnected, attempting to reconnect...", "warning");
    try {
      const newWebsocket = await connect(options);
      isReconnecting = false;
      setUpAutoReconnect(options, newWebsocket);
    } catch (error) {
      log("Reconnection attempt failed.", "error");
      isReconnecting = false;
      attemptReconnection(options);
    }
  }, reconnectDelay);
};

const setUpAutoReconnect = async (
  options: Options,
  websocket: HostipWebSocket,
) => {
  // We can only reliably reconnect custom subdomains. Otherwise you'd get another random subdomain on reconnection
  if (typeof options.domain !== "string") {
    return;
  }

  // Set up the websocket connection to auto reconnect
  websocket.on("close", () => {
    attemptReconnection(options);
  });

  resetTheConnectionAttemptsInterval();
};

export { setUpAutoReconnect };