apollo-portal/src/main/java/com/ctrip/framework/apollo/portal/api/AdminServiceAPI.java/AdminServiceAPI/loadCluster
class AdminServiceAPI:    public ClusterDTO loadCluster(String appId, Env env, String clusterName) {
      return restTemplate.get(env, "apps/{appId}/clusters/{clusterName}", ClusterDTO.class,
          appId, clusterName);
    }