@Override
    public List<InetSocketAddress> lookup(String key) throws Exception {
        String clusterName = getServiceGroup(key);

        if (clusterName == null) {
            String missingDataId = PREFIX_SERVICE_ROOT + CONFIG_SPLIT_CHAR + PREFIX_SERVICE_MAPPING + key;
            throw new ConfigNotFoundException("%s configuration item is required", missingDataId);
        }

        return doLookup(clusterName);
    }
@Test
    public void testLookUp() throws Exception {
        ZookeeperRegisterServiceImpl zookeeperRegisterService = ZookeeperRegisterServiceImpl.getInstance();

        ZkClient client = service.buildZkClient("127.0.0.1:2181", 5000, 5000);
        client.createPersistent("/registry/zk/cluster");
        client.createEphemeral("/registry/zk/cluster/127.0.0.1:8091");

        Field field = ZookeeperRegisterServiceImpl.class.getDeclaredField("zkClient");
        field.setAccessible(true);
        field.set(zookeeperRegisterService, client);


        System.setProperty("txServiceGroup", "default_tx_group");
        System.setProperty("service.vgroupMapping.default_tx_group", "cluster");


        List<InetSocketAddress> addressList = zookeeperRegisterService.lookup("default_tx_group");

        Assertions.assertEquals(addressList, Collections.singletonList(new InetSocketAddress("127.0.0.1", 8091)));
    }