請(qǐng)勿過度依賴Redis的過期監(jiān)聽

作者：迪殼

https://juejin.im/post/6844904158227595271

Redis 過期監(jiān)聽場(chǎng)景

業(yè)務(wù)中有類似等待一定時(shí)間之后執(zhí)行某種行為的需求 , 比如 30 分鐘之后關(guān)閉訂單 . 網(wǎng)上有很多使用 Redis 過期監(jiān)聽的 Demo , 但是其實(shí)這是個(gè)大坑 , 因?yàn)?Redis 不能確保 key 在指定時(shí)間被刪除 , 也就造成了通知的延期 . 不多說 , 跑個(gè)測(cè)試

測(cè)試情況

先說環(huán)境 , redis 運(yùn)行在 Docker 容器中 , 分配了 一個(gè) cpu 以及 512MB 內(nèi)存, 在 Docker 中執(zhí)行?redis-benchmark -t set -r 100000 -n 1000000?結(jié)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(shí)這里有些不嚴(yán)謹(jǐn)?benchmark?線程不應(yīng)該在 Docker 容器內(nèi)部運(yùn)行 . 跑分的時(shí)候大概?benchmark?和 redis 主線程各自持有 50%CPU

測(cè)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(shè)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(shè)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(shí) 56 分的時(shí)候 , 會(huì)增加一批在接下來 16 小時(shí)過期的 key , 過期時(shí)間間隔 8 秒 , 且過期時(shí)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