apollo-openapi/src/main/java/com/ctrip/framework/apollo/openapi/client/ApolloOpenApiClient.java/ApolloOpenApiClient/getCluster
class ApolloOpenApiClient:  public OpenClusterDTO getCluster(String appId, String env, String clusterName) {
    return clusterService.getCluster(appId, env, clusterName);
  }