Subscribe to Zookeeper events only after application starts

Sometimes ZK events came before the app start, causing repartition change events, while event listeners are not yet initialized by Spring

common/queue/src/main/java/org/thingsboard/server/queue/discovery/ZkDiscoveryService.java

@@ -143,6 +143,7 @@ public class ZkDiscoveryService implements DiscoveryService, PathChildrenCacheLi
         } else {
             log.info("Received application ready event. Starting current ZK node.");
         }
+        subscribeToEvents();
         if (client.getState() != CuratorFrameworkState.STARTED) {
             log.debug("Ignoring application ready event, ZK client is not started, ZK client state [{}]", client.getState());
             return;
@@ -212,6 +213,7 @@ public class ZkDiscoveryService implements DiscoveryService, PathChildrenCacheLi
             try {
                 destroyZkClient();
                 initZkClient();
+                subscribeToEvents();
                 publishCurrentServer();
             } catch (Exception e) {
                 log.error("Failed to reconnect to ZK: {}", e.getMessage(), e);
@@ -227,7 +229,6 @@ public class ZkDiscoveryService implements DiscoveryService, PathChildrenCacheLi
             client.start();
             client.blockUntilConnected();
             cache = new PathChildrenCache(client, zkNodesDir, true);
-            cache.getListenable().addListener(this);
             cache.start();
             stopped = false;
             log.info("ZK client connected");
@@ -239,6 +240,10 @@ public class ZkDiscoveryService implements DiscoveryService, PathChildrenCacheLi
         }
     }
 
+    private void subscribeToEvents() {
+        cache.getListenable().addListener(this);
+    }
+
     private void unpublishCurrentServer() {
         try {
             if (nodePath != null) {