Implement queue for Xiaomi router polling. https://github.com/Koenkk/zigbee2mqtt/issues/927

lib/extension/routerPollXiaomi.js

@@ -1,5 +1,7 @@
 const utils = require('../util/utils');
 const interval = utils.secondsToMilliseconds(60);
+const Queue = require('queue');
+const logger = require('../util/logger');
 
 /**
  * This extensions polls Xiaomi Zigbee routers to keep them awake.
@@ -8,6 +10,15 @@ class RouterPollXiaomi {
     constructor(zigbee, mqtt, state, publishDeviceState) {
         this.zigbee = zigbee;
         this.timer = null;
+
+        /**
+         * Setup command queue.
+         * The command queue ensures that only 1 command is executed at a time.
+         * This is to avoid DDoSiNg of the coordinator.
+         */
+        this.queue = new Queue();
+        this.queue.concurrency = 1;
+        this.queue.autostart = true;
     }
 
     onZigbeeStarted() {
@@ -27,15 +38,30 @@ class RouterPollXiaomi {
     }
 
     stop() {
+        this.queue.stop();
         this.clearTimer();
     }
 
+    ping(ieeeAddr) {
+        this.queue.push((queueCallback) => {
+            this.zigbee.ping(ieeeAddr, (error) => {
+                if (error) {
+                    logger.debug(`Failed to ping ${ieeeAddr}`);
+                } else {
+                    logger.debug(`Successfully pinged ${ieeeAddr}`);
+                }
+
+                queueCallback();
+            });
+        });
+    }
+
     handleInterval() {
         this.zigbee.getAllClients()
             .filter((d) => utils.isXiaomiDevice(d)) // Filter Xiaomi devices
             .filter((d) => d.type === 'Router') // Filter routers
             .filter((d) => d.powerSource && d.powerSource !== 'Battery') // Remove battery powered devices
-            .forEach((d) => this.zigbee.ping(d.ieeeAddr)); // Ping devices.
+            .forEach((d) => this.ping(d.ieeeAddr)); // Ping devices.
     }
 }