public static Set<String> fetchMasterAddrByClusterName(final MQAdminExt adminExt, final String clusterName)
        throws InterruptedException, RemotingConnectException, RemotingTimeoutException,
        RemotingSendRequestException, MQBrokerException {
        Set<String> masterSet = new HashSet<>();

        ClusterInfo clusterInfoSerializeWrapper = adminExt.examineBrokerClusterInfo();

        Set<String> brokerNameSet = clusterInfoSerializeWrapper.getClusterAddrTable().get(clusterName);

        if (brokerNameSet != null) {
            for (String brokerName : brokerNameSet) {
                BrokerData brokerData = clusterInfoSerializeWrapper.getBrokerAddrTable().get(brokerName);
                if (brokerData != null) {

                    String addr = brokerData.getBrokerAddrs().get(MixAll.MASTER_ID);
                    if (addr != null) {
                        masterSet.add(addr);
                    }
                }
            }
        } else {
            System.out.printf("[error] %s", ERROR_MESSAGE);
        }

        return masterSet;
    }
@Test
    public void testFetchMasterAddrByClusterName() throws InterruptedException, MQBrokerException, RemotingTimeoutException, RemotingSendRequestException, RemotingConnectException {
        Set<String> result = CommandUtil.fetchMasterAddrByClusterName(defaultMQAdminExtImpl, "default-cluster");
        assertThat(result.size()).isEqualTo(0);
    }