@Override
    public String ping(RedisClusterNode node) {
        RedisClient entry = getEntry(node);
        RFuture<String> f = executorService.readAsync(entry, LongCodec.INSTANCE, RedisCommands.PING);
        return syncFuture(f);
    }
@Test
    public void testClusterPing() {
        RedisClusterNode master = getFirstMaster();
        String res = connection.ping(master);
        assertThat(res).isEqualTo("PONG");
    }