程序員的成長之路

互聯(lián)網(wǎng)/程序員/技術/資料共享?

閱讀本文大概需要 5?分鐘。

來自：juejin.im/post/6844904158227595271

Redis 過期監(jiān)聽場景

業(yè)務中有類似等待一定時間之后執(zhí)行某種行為的需求 , 比如 30 分鐘之后關閉訂單 . 網(wǎng)上有很多使用 Redis 過期監(jiān)聽的 Demo , 但是其實這是個大坑 , 因為 Redis 不能確保 key 在指定時間被刪除 , 也就造成了通知的延期 . 不多說 , 跑個測試。

測試情況

先說環(huán)境 , redis 運行在 Docker 容器中 , 分配了 一個 cpu 以及 512MB 內存, 在 Docker 中執(zhí)行?redis-benchmark -t set -r 100000 -n 1000000?結果如下:

\======?SET?======
??1000000?requests?completed?in?171.03?seconds
??50?parallel?clients
??3?bytes?payload
??keep?alive:?1
??host?configuration?"save":?3600?1?300?100?60?10000
??host?configuration?"appendonly":?no
??multi-thread:?no

其實這里有些不嚴謹?benchmark?線程不應該在 Docker 容器內部運行 . 跑分的時候大概 benchmark 和 redis 主線程各自持有 50%CPU

測試代碼如下:

@Service
@Slf4j
public?class?RedisJob?{
????@Autowired
????private?StringRedisTemplate?stringRedisTemplate;

????public?DateTimeFormatter?dateTimeFormatter?=?DateTimeFormatter.ofPattern("yyyy-MM-dd?HH:mm:ss");
????public?LocalDateTime?end?=?LocalDateTime.of(LocalDate.of(2020,?5,?12),?LocalTime.of(8,?0));

????@Scheduled(cron?=?"0?56?\*?\*?\*??")
????public?void?initKeys()?{
????????LocalDateTime?now?=?LocalDateTime.now();
????????ValueOperations?operations?=?stringRedisTemplate.opsForValue();
????????log.info("開始設置key");
????????LocalDateTime?begin?=?now.withMinute(0).withSecond(0).withNano(0);
????????for?(int?i?=?1;?i?17;?i++)?{
????????????setExpireKey(begin.plusHours(i),?8,?operations);
????????}
????????log.info("設置完畢:?"?+?Duration.between(now,?LocalDateTime.now()));
????}

????private?void?setExpireKey(LocalDateTime?expireTime,?int?step,?ValueOperations?operations)?{
????????LocalDateTime?localDateTime?=?LocalDateTime.now().withNano(0);
????????String?nowTime?=?dateTimeFormatter.format(localDateTime);
????????while?(expireTime.getMinute()?55)?{
????????????operations.set(nowTime?+?"@"?+?dateTimeFormatter.format(expireTime),?"A",?Duration.between(expireTime,?LocalDateTime.now()).abs());
????????????expireTime?=?expireTime.plusSeconds(step);
????????}
????}
}

大概意思就是每小時 56 分的時候 , 會增加一批在接下來 16 小時過期的 key , 過期時間間隔 8 秒 , 且過期時間都在 55 分之前

@Slf4j
@Component
public?class?RedisKeyExpirationListener?extends?KeyExpirationEventMessageListener?{

????public?RedisKeyExpirationListener(RedisMessageListenerContainer?listenerContainer)?{
????????super(listenerContainer);
????}

????public?DateTimeFormatter?dateTimeFormatter?=?DateTimeFormatter.ofPattern("yyyy-MM-dd?HH:mm:ss");
????@Autowired
????private?StringRedisTemplate?stringRedisTemplate;


????@Override
????public?void?onMessage(Message?message,?byte\[\]?pattern)?{
????????String?keyName?=?new?String(message.getBody());
????????LocalDateTime?parse?=?LocalDateTime.parse(keyName.split("@")\[1\],?dateTimeFormatter);
????????long?seconds?=?Duration.between(parse,?LocalDateTime.now()).getSeconds();
????????stringRedisTemplate.execute((RedisCallback