聊聊redisson的分布式锁

序

本文主要研究一下redisson的分布式锁

maven

        
            org.redisson
            redisson
            3.8.1
        

实例

    @Test
    public void testDistributedLock(){
        Config config = new Config();
//        config.setTransportMode(TransportMode.EPOLL);
        config.useSingleServer()
                .setAddress("redis://192.168.99.100:6379");
        RedissonClient redisson = Redisson.create(config);


        IntStream.rangeClosed(1,5)
                .parallel()
                .forEach(i -> {
                    executeLock(redisson);
                });

        executeLock(redisson);
    }

    public void executeLock(RedissonClient redisson){
        RLock lock = redisson.getLock("myLock");
        boolean locked = false;
        try{
            LOGGER.info("try lock");
            locked = lock.tryLock();
//            locked = lock.tryLock(1,2,TimeUnit.MINUTES);
            LOGGER.info("get lock result:{}",locked);
            if(locked){
                TimeUnit.HOURS.sleep(1);
                LOGGER.info("get lock and finish");
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            LOGGER.info("enter unlock");
            if(locked){
                lock.unlock();
            }
        }
    }

源码解析

RedissonLock.tryLock

redisson-3.8.1-sources.jar!/org/redisson/RedissonLock.java

    @Override
    public boolean tryLock() {
        return get(tryLockAsync());
    }

    @Override
    public RFuture tryLockAsync() {
        return tryLockAsync(Thread.currentThread().getId());
    }

    @Override
    public RFuture tryLockAsync(long threadId) {
        return tryAcquireOnceAsync(-1, null, threadId);
    }

    private RFuture tryAcquireOnceAsync(long leaseTime, TimeUnit unit, final long threadId) {
        if (leaseTime != -1) {
            return tryLockInnerAsync(leaseTime, unit, threadId, RedisCommands.EVAL_NULL_BOOLEAN);
        }
        RFuture ttlRemainingFuture = tryLockInnerAsync(commandExecutor.getConnectionManager().getCfg().getLockWatchdogTimeout(), TimeUnit.MILLISECONDS, threadId, RedisCommands.EVAL_NULL_BOOLEAN);
        ttlRemainingFuture.addListener(new FutureListener() {
            @Override
            public void operationComplete(Future future) throws Exception {
                if (!future.isSuccess()) {
                    return;
                }

                Boolean ttlRemaining = future.getNow();
                // lock acquired
                if (ttlRemaining) {
                    scheduleExpirationRenewal(threadId);
                }
            }
        });
        return ttlRemainingFuture;
    }

     RFuture tryLockInnerAsync(long leaseTime, TimeUnit unit, long threadId, RedisStrictCommand command) {
        internalLockLeaseTime = unit.toMillis(leaseTime);

        return commandExecutor.evalWriteAsync(getName(), LongCodec.INSTANCE, command,
                  "if (redis.call('exists', KEYS[1]) == 0) then " +
                      "redis.call('hset', KEYS[1], ARGV[2], 1); " +
                      "redis.call('pexpire', KEYS[1], ARGV[1]); " +
                      "return nil; " +
                  "end; " +
                  "if (redis.call('hexists', KEYS[1], ARGV[2]) == 1) then " +
                      "redis.call('hincrby', KEYS[1], ARGV[2], 1); " +
                      "redis.call('pexpire', KEYS[1], ARGV[1]); " +
                      "return nil; " +
                  "end; " +
                  "return redis.call('pttl', KEYS[1]);",
                    Collections.