做谷粒商城练习时P46，发现网关gateway转发到renren-fast获取验证码报503，原因是我在commom模块里引入的nacos排除了ribbon，所以无法通过lb路由到指定微服务

      <dependency>
            <groupId>com.alibaba.cloud</groupId>
            <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.cloud</groupId>
                    <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
                </exclusion>
            </exclusions>
      </dependency>

解决方法：在gateway里引入loadbalancer依赖

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-loadbalancer</artifactId>
        </dependency>