MMM-Remote-Control

[rkorell]

@KristjanESPERANTO Dear Kristijan,

after a long time I finally managed to see your “new” modul.
First of all: Thanks a lot for your effort, again - nice piece!

In the past few days I’ve completely rebuilt my mirror and migrated it to trixie as well as to the actual mirror and node versions.

I ran into a reproducible issue with the restart functionality when MagicMirror is managed by pm2 (which is the recommended setup per the official MagicMirror documentation).

The Problem

When triggering a restart via the Remote-Control UI (or the /api/restart endpoint), MagicMirror enters an endless crash-loop with EADDRINUSE: address already in use :::8080.

Root Cause
The handleRestart function in node_helper.js (lines 717-741) uses the Electron-native restart mechanism:

const {app} = require("electron");
app.relaunch();
app.quit();

This works fine in standalone mode, but creates a race condition with pm2:

1. app.relaunch() spawns a new Electron instance (child of the current process)
2. app.quit() terminates the current Electron instance
3. pm2 detects the termination as a crash and spawns another Electron instance
4. Now two Electron instances compete for port 8080 → EADDRINUSE → both crash → pm2 keeps restarting → infinite loop

The only way to recover is to manually identify and kill the orphaned Electron process, then trigger a clean restart via touch config.js (which pm2’s file-watch picks up).

Interestingly, the catch-block fallback for server mode (lines 726-739) already does it correctly — it calls process.exit(0) and lets the process manager handle the restart. The Electron code path just doesn’t account for the pm2 scenario.

Possible Fix

When running under pm2, the Electron-native app.relaunch() should be skipped entirely.

pm2 can be detected via environment variables like PM2_HOME, pm_id, or PM2_USAGE:

handleRestart (query, res) {
  try {
    const {app} = require("electron");
    if (!app) { throw "Could not get Electron app instance."; }

    // When running under pm2, don't use app.relaunch() — pm2 handles restart
    if (process.env.PM2_HOME || process.env.pm_id !== undefined) {
      Log.log("Running under pm2, exiting cleanly for process manager restart...");
      this.sendResponse(res, undefined, {action: "RESTART", info: "Exiting for pm2 restart..."});
      setTimeout(() => app.quit(), 1000);
      return;
    }

    this.sendResponse(res, undefined, {action: "RESTART", info: "Restarting Electron..."});
    app.relaunch();
    app.quit();
  } catch (error) {
    // ... existing server mode fallback ...
  }
}

Environment

• MagicMirror 2.34.0
• MMM-Remote-Control 4.2.2 (commit b854832)
• Node.js v22, Electron 39.5.2
• Raspberry Pi 5, Debian 13 (Trixie)
• Process manager: pm2 with file-watch on config.js

Workaround

For now, I’ve documented this for my setup: never use the restart button in Remote-Control. Monitor ON/OFF works fine, only the restart is
affected.

Thanks for considering this — happy to test any fix if needed!

Warmest regards,
Ralf

[KristjanESPERANTO]

Hi @vtek, glad you figured it out! Just for reference: when secureEndpoints: true is set, the API key can be passed in two ways:

1. URL parameter: ?apiKey=YOUR_KEY
2. HTTP header: Authorization: apiKey YOUR_KEY

Also, starting with v4.2.4 the error message now directly hints at the solution, so the next person running into this should find it faster 🙂

[KristjanESPERANTO]

Hi @rkorell, thank you for the detailed bug report — the root cause analysis was spot on and made it straightforward to fix!

The fix is included in v4.2.4: when MMM-Remote-Control detects it’s running under pm2 (via PM2_HOME or pm_id environment variables), it now skips app.relaunch() and only calls app.quit(), letting pm2 handle the restart cleanly.

Would be great if you could confirm it works on your setup!

[rkorell]

@KristjanESPERANTO Dear Kristijan,
just tested v4.2.4 — works perfectly! Restart via the Remote-Control UI now completes cleanly
under pm2, no orphaned Electron process, no port conflict. Exactly the behavior you’d expect.

I also noticed you added a dedicated handleRestart.test.js with 210 lines of unit tests covering
both the pm2 and standalone code paths — that’s really impressive and goes well beyond just a
quick fix. Having proper test coverage for this kind of dual-mode behavior is exactly the right
thing to do. Much appreciated!

Thanks for the incredibly fast turnaround and the quality of the fix. Consider this confirmed
working on:

• MagicMirror 2.34.0
• MMM-Remote-Control 4.2.4
• Node.js v22, Electron 39.5.2
• Raspberry Pi 5, Debian 13 (Trixie)
• pm2 with file-watch

Warmest regards,
Ralf

[KristjanESPERANTO]

@rkorell Thank you very much for this feedback and appreciation 🙂 It’s interesting that you took a deeper look at the changes.