[GitHub] [dubbo] plusmancn edited a comment on issue #8599: triple不支持应用级地址发现

[GitBox <gi...@apache.org>]

plusmancn edited a comment on issue #8599:
URL: https://github.com/apache/dubbo/issues/8599#issuecomment-912218330


   @feng996  I have found the cause of the problem which is not related to `dubbo-spring-boot-starter` as I first thought.
   
   The source is in `org.apache.dubbo.config.metadata.ServiceInstanceHostPortCustomizer`, let's have a look:
   ```java
   @Override
   public void customize(ServiceInstance serviceInstance) {
       String host = null;
       int port = -1;
       // ......
       Set<URL> urls = writableMetadataService.getExportedServiceURLs();
       if (CollectionUtils.isNotEmpty(urls)) {
           ApplicationModel applicationModel = serviceInstance.getApplicationModel();
           String preferredProtocol = applicationModel.getCurrentConfig().getProtocol();
           //  The default value of preferredProtocol is dubbo.
           if (preferredProtocol != null) {
               for (URL exportedURL : urls) {
                   // The protocol of exportedURL is tri
                   // because of tri != dubbo, the host and port will not be assigned values.
                   if (preferredProtocol.equals(exportedURL.getProtocol())) {
                       host = exportedURL.getHost();
                       port = exportedURL.getPort();
                       break;
                   }
               }
           } else {
               URL url = urls.iterator().next();
               host = url.getHost();
               port = url.getPort();
           }
           // If not the port of instace > 0, the application instance will not be registered to RegistryCenter(like Nacos, Zookeeper).
           // As a result, the consumer can't find the avaliabe providers when our settging is registry-mode=instance
           if (serviceInstance instanceof DefaultServiceInstance) {
               DefaultServiceInstance instance = (DefaultServiceInstance) serviceInstance;
               instance.setHost(host);
               instance.setPort(port);
           }
       }
   }
   ```
   
   For the moment, if you want both consumer and provider to force using `Application Discovery` in tri protocol, just change one line config of provider as follows:
   ```yaml
   dubbo:
     application:
       metadata-type: remote
       register-mode: instance
       protocol: tri  <==== HERE, set preferredProtocol as tri
   ```
   
   But, Dubbo official also needs to do two things for further promotion:
   1. Complete the docs: [Triple协议迁移指南](https://dubbo.apache.org/zh/docs/migration/migration-triple/) as soon as possible
   2. The logic of preferredProtocol was not user-friendly, we maybe should optimize it.


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