Use mutex in persistent storage

Author: mpatfield

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 All notable changes to homebridge-dummy will be documented in this file.
 
-## 1.5.16-beta.0 ()
+## 1.5.16-beta.1 ()
 
 ### Added
 - Added `topicGetAvailable` for "Last Will and Testament" (LWT) before an accessory goes offline
@@ -11,6 +11,9 @@ All notable changes to homebridge-dummy will be documented in this file.
 ### Changed
 - Renamed "Get Availability" to "Get Active Status" in config UI to avoid confusion with the new `topicGetAvailable` (see above)
 
+### Fixed
+- Potential race condition in persistent storage
+
 ## 1.5.15 (2026-05-12)
 
 ### Fixed

package-lock.json

@@ -4,7 +4,7 @@
   "displayName": "Homebridge Easy MQTT",
   "description": "Homebridge plugin for MQTT devices",
   "type": "module",
-  "version": "1.5.16-beta.0",
+  "version": "1.5.16-beta.1",
   "homepage": "https://github.com/mpatfield/homebridge-easy-mqtt#readme",
   "repository": {
     "type": "git",

package.json

@@ -0,0 +1,16 @@
+export class Mutex {
+
+  private _lock: Promise<void> = Promise.resolve();
+
+  public async lock<T>(fn: () => T | Promise<T>): Promise<T> {
+    const prev = this._lock;
+    let release!: () => void;
+    this._lock = new Promise(r => release = r);
+    await prev;
+    try {
+      return await fn();
+    } finally {
+      release();
+    }
+  }
+}

src/tools/mutex.ts

@@ -1,11 +1,15 @@
 import { PrimitiveTypes } from 'homebridge';
 import storage from 'node-persist';
 
+import { Mutex } from './mutex.js';
+
 import { PLATFORM_NAME } from '../homebridge/settings.js';
 
 type Storable = PrimitiveTypes | PrimitiveTypes[] | { [key: string]: PrimitiveTypes };
 const PROPERTIES = new Map<string, Map<string, Storable>>();
 
+const MUTEX = new Mutex();
+
 export class Properties {
 
   public static async initStorage(persistPath: string) {
@@ -66,6 +70,12 @@ export class Properties {
   }
 
   private static async save() {
+    await MUTEX.lock(async () => {
+      await Properties._save();
+    });
+  }
+
+  private static async _save() {
     const storageArray = Array.from(PROPERTIES.entries()).map(([key, value]) => {
       return [key, Array.from(value.entries())];
     });