404008945 commented on issue #10393:
URL: https://github.com/apache/dubbo/issues/10393#issuecomment-1206584496
> @404008945 provider 和 consumer 都升级，2.7 的早期有个版本注册是有问题的
问题找到了。
生产和消费者都是升级了最新版的2.7.16，另外nacos-client为1.3.3时有问题，**测试nacos-client版本为2.0.4已经没有问题了**
**问题记录**
生产者注册服务名称逻辑为
org.apache.dubbo.common.URL#getColonSeparatedKey
```java
public String getColonSeparatedKey() {
StringBuilder serviceNameBuilder = new StringBuilder();
serviceNameBuilder.append(this.getServiceInterface());
append(serviceNameBuilder, VERSION_KEY, false);
append(serviceNameBuilder, GROUP_KEY, false);
return serviceNameBuilder.toString();
}
```
当version为空时并不会省略掉间隔符冒号
于是注册的服务名称是
io.seata.samples.tcc.dubbo.action.TccActionOne::tcc
然后我又看了消费者启动时初始化invoke时，生成的订阅服务名称逻辑
org.apache.dubbo.registry.nacos.NacosRegistry#getServiceNames0
```java
private Set<String> getServiceNames0(URL url) {
NacosServiceName serviceName = createServiceName(url);
final Set<String> serviceNames;
if (serviceName.isConcrete()) { // is the concrete service name
serviceNames = new LinkedHashSet<>();
serviceNames.add(serviceName.toString());
// Add the legacy service name since 2.7.6
String legacySubscribedServiceName =
getLegacySubscribedServiceName(url);
if (!serviceName.toString().equals(legacySubscribedServiceName))
{
//avoid duplicated service names
serviceNames.add(legacySubscribedServiceName);
}
} else {
serviceNames = filterServiceNames(serviceName);
}
return serviceNames;
}
```
version为空，新版服务名version为空，不会省略间隔符冒号,根据注释，为了兼容2.7.3以前的版本，另外生成服务名
version为空并且把冒号也省略掉了。最终结果就是新版比旧版多了一个冒号。
后面会继续分别订阅这两个服务名称,其中一个服务名在注册中心不存在，是空服务。
org.apache.dubbo.registry.nacos.NacosRegistry#doSubscribe(org.apache.dubbo.common.URL,
org.apache.dubbo.registry.NotifyListener, java.util.Set<java.lang.String>)
```java
private void doSubscribe(final URL url, final NotifyListener listener,
final Set<String> serviceNames) {
execute(namingService -> {
if (isServiceNamesWithCompatibleMode(url)) {
List<Instance> allCorrespondingInstanceList =
Lists.newArrayList();
/**
* Get all instances with serviceNames to avoid instance
overwrite and but with empty instance mentioned
* in https://github.com/apache/dubbo/issues/5885 and
https://github.com/apache/dubbo/issues/5899
*
* namingService.getAllInstances with {@link
org.apache.dubbo.registry.support.AbstractRegistry#registryUrl}
* default {@link DEFAULT_GROUP}
*
* in https://github.com/apache/dubbo/issues/5978
*/
for (String serviceName : serviceNames) {
List<Instance> instances =
namingService.getAllInstances(serviceName,
getUrl().getParameter(GROUP_KEY,
Constants.DEFAULT_GROUP));
NacosInstanceManageUtil.initOrRefreshServiceInstanceList(serviceName,
instances);
allCorrespondingInstanceList.addAll(instances);
}
notifySubscriber(url, listener,
allCorrespondingInstanceList);
for (String serviceName : serviceNames) {
subscribeEventListener(serviceName, url, listener);
}
} else {
List<Instance> instances = new LinkedList<>();
for (String serviceName : serviceNames) {
instances.addAll(namingService.getAllInstances(serviceName
, getUrl().getParameter(GROUP_KEY,
Constants.DEFAULT_GROUP)));
notifySubscriber(url, listener, instances);
subscribeEventListener(serviceName, url, listener);
}
}
});
}
```
上面有段很好的注释 ，**Get all instances with serviceNames to avoid instance overwrite
and but with empty instance mentioned**获取所有的serviceNames
的实例，防止被空的实例覆盖。看起来好像没有问题。
但是下面的循环serviceNames订阅
```java
for (String serviceName : serviceNames) {
subscribeEventListener(serviceName, url, listener);
}
```
但是注册中心为nacos时
这里来到了nacos客户端 版本为1.3.3时
```java
public void addListener(ServiceInfo serviceInfo, String clusters,
EventListener listener) {
NAMING_LOGGER.info("[LISTENER] adding " + serviceInfo.getName() + "
with " + clusters + " to listener map");
List<EventListener> observers = Collections.synchronizedList(new
ArrayList<EventListener>());
observers.add(listener);
observers =
observerMap.putIfAbsent(ServiceInfo.getKey(serviceInfo.getName(), clusters),
observers);
if (observers != null) {
observers.add(listener);
}
serviceChanged(serviceInfo);
}
```
会发现在第一次添加监听器时还是会触发serviceChange，进而触发notify，重新刷新invoker，由于实例为空的服务名也被订阅，那么这时候还是可能会发生被空的实例覆盖的情况。
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