- [ ] I have searched the [issues](https://github.com/apache/dubbo/issues) of this repository and believe that this is not a duplicate.
- [ ] I have checked the [FAQ](https://github.com/apache/dubbo/blob/master/FAQ.md) of this repository and believe that this is not a duplicate.

### Environment

* Dubbo version: xxx
* Operating System version: xxx
* Java version: xxx

### Steps to reproduce this issue

1. xxx
2. xxx
3. xxx

Pls. provide [GitHub address] to reproduce this issue.

### Expected Result

What do you expected from the above steps？

### Actual Result

What actually happens?

If there is an exception, please attach the exception trace:

```
Just put your stack trace here!
```

}
        }
        return urls;
    }
    private void subscribeEventListener(String serviceName, final URL url, final NotifyListener listener)
            throws NacosException {
        EventListener eventListener = new RegistryChildListenerImpl(serviceName, url, listener);
        namingService.subscribe(serviceName,
                getUrl().getGroup(Constants.DEFAULT_GROUP),
                eventListener);
    }
    /**
     * Notify the Enabled {@link Instance instances} to subscriber.
     *
     * @param url       {@link URL}
     * @param listener  {@link NotifyListener}
     * @param instances all {@link Instance instances}
     */
    private void notifySubscriber(URL url, NotifyListener listener, Collection<Instance> instances) {
        List<Instance> enabledInstances = new LinkedList<>(instances);
        if (enabledInstances.size() > 0) {
            
            filterEnabledInstances(enabledInstances);
        }
        List<URL> urls = toUrlWithEmpty(url, enabledInstances);
        NacosRegistry.this.notify(url, listener, urls);
    }
    /**
     * Get the categories from {@link URL}
     *