- [ ] 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!
```

private static final long LOOKUP_INTERVAL = Long.getLong("nacos.service.names.lookup.interval", 30);
    /**
     * {@link ScheduledExecutorService} lookup Nacos service names(only for Dubbo-OPS)
     */
    private volatile ScheduledExecutorService scheduledExecutorService;
    private static final Logger logger = LoggerFactory.getLogger(NacosRegistry.class);
    private final NacosNamingServiceWrapper namingService;
    public NacosRegistry(URL url, NacosNamingServiceWrapper namingService) {
        super(url);
        this.namingService = namingService;
    }
    @Override
    public boolean isAvailable() {
        return "UP".equals(namingService.getServerStatus());
    }
    @Override
    public List<URL> lookup(final URL url) {
        if(url == null){
            throw new IllegalArgumentException("lookup url == null");
        }
        try{
            List<URL> urls = new LinkedList<>();
            Set<String> serviceNames = getServiceNames(url, null);
            for (String serviceName : serviceNames) {
                List<Instance> instances = namingService.getAllInstances(serviceName,
                    getUrl().getGroup(Constants.DEFAULT_GROUP));
                urls.addAll(buildURLs(url, instances));
            }
            return urls;
        }catch (Throwable cause){