分布式redis锁代码实现

悠悠 2023-01-11 14:27 111阅读 0赞

@Component
    public class RedisDistributedLock extends AbstractDistributedLock {
        @Autowired
        private RedisTemplate<String, Object> redisTemplate;
    
        private ThreadLocal<String> lockFlag = new ThreadLocal<>();
    
        private static final String UNLOCK_LUA;
    
        /*
         * 通过lua脚本释放锁,来达到释放锁的原子操作
         */
        static {
            UNLOCK_LUA = "if redis.call(\"get\",KEYS[1]) == ARGV[1] " +
                    "then " +
                    "    return redis.call(\"del\",KEYS[1]) " +
                    "else " +
                    "    return 0 " +
                    "end ";
        }
    
        public RedisDistributedLock(RedisTemplate<String, Object> redisTemplate) {
            super();
            this.redisTemplate = redisTemplate;
        }
    
        @Override
        public boolean lock(String key, long expire, int retryTimes, long sleepMillis) {
            boolean result = setRedis(key, expire);
            // 如果获取锁失败，按照传入的重试次数进行重试
            while ((!result) && retryTimes-- > 0) {
                try {
                    log.debug("get redisDistributeLock failed, retrying..." + retryTimes);
                    Thread.sleep(sleepMillis);
                } catch (InterruptedException e) {
                    //中断 后不在尝试获取
                    retryTimes = 0;
                    log.warn("Interrupted!", e);
                    Thread.currentThread().interrupt();
                }
                result = setRedis(key, expire);
            }
            return result;
        }
    
        private Boolean setRedis(final String key, final long expire) {
            try {
                return redisTemplate.execute((RedisCallback<Boolean>) connection -> {
                    String uuid = UUID.randomUUID().toString();
                    lockFlag.set(uuid);
                    byte[] keyByte = redisTemplate.getStringSerializer().serialize(key);
                    byte[] uuidByte = redisTemplate.getStringSerializer().serialize(uuid);
                    if (keyByte==null || uuidByte==null){
                        return false;
                    }
                    return connection.set(keyByte, uuidByte, Expiration.from(expire, TimeUnit.MILLISECONDS), RedisStringCommands.SetOption.ifAbsent());
                });
            } catch (Exception e) {
                log.error("set redisDistributeLock occured an exception", e);
            }
            return false;
        }
    
        @Override
        public boolean releaseLock(String key) {
            // 释放锁的时候，有可能因为持锁之后方法执行时间大于锁的有效期，此时有可能已经被另外一个线程持有锁，所以不能直接删除
            try {
                // 使用lua脚本删除redis中匹配value的key，可以避免由于方法执行时间过长而redis锁自动过期失效的时候误删其他线程的锁
                // spring自带的执行脚本方法中，集群模式直接抛出不支持执行脚本的异常，所以只能拿到原redis的connection来执行脚本
                Boolean result = redisTemplate.execute((RedisCallback<Boolean>) connection -> {
                    byte[] scriptByte = redisTemplate.getStringSerializer().serialize(UNLOCK_LUA);
                    return connection.eval(scriptByte,  ReturnType.BOOLEAN, 1
                            , redisTemplate.getStringSerializer().serialize(key)
                            , redisTemplate.getStringSerializer().serialize(lockFlag.get()));
                });
                return result;
            } catch (Exception e) {
                log.error("release redisDistributeLock occured an exception", e);
            } finally {
                lockFlag.remove();
            }
            return false;
        }
    
        @Override
        public String getLockFlag(){
            return lockFlag.get();
        }
    
        @Override
        public void setLockFlag(String str){
            lockFlag.set(str);
        }
    }