微服务最佳实践，零改造实现 Spring Cloud

[samples/dubbo-call-sc](https://github.com/apache/dubbo-samples/tree/master/2-advanced/dubbo-samples-springcloud/dubbo-call-sc)；源码dubbo访问sc,服务，启动报错：Application run failed
org.apache.dubbo.rpc.RpcException: No provider available from registry RegistryDirectory(registry: 127.0.0.1:8848)-Directory(invokers: 0[], validInvokers: 0[], invokersToReconnect: 0[]) for service org.apache.dubbo.samples.sc.UserServiceFeign2 on consumer 100.100.100.45 use dubbo version 3.3.1, please check status of providers(disabled, not registered or in blocklist).

Start with samples/dubbo-call-sc in the linked sample and run it with Dubbo 3.3.1. Check why the provider for org.apache.dubbo.samples.sc.UserServiceFeign2 is not registered at 127.0.0.1:8848; done means the sample starts without the No provider available error.

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