一、RedissonReadLock#unlock 源码分析

上一篇已经简单介绍了，redisson 提供的读写锁 RReadWriteLock 的使用demo、使用场景、和RedissonLock 的关系；也深入分析了读锁 RedissonReadLock 加锁 lua 脚本的执行逻辑、watchdog 机制 lua 脚本的执行逻辑。

下面，我们将继续分析读锁 RedissonReadLock 释放锁时，lua 脚本是怎么执行的。

1、RedissonReadLock 释放锁 lua 脚本分析

分析前，我们定一下加锁的key：

RReadWriteLock readWriteLock = client.getReadWriteLock("myLock");

RedissonReadLock#unlockInnerAsync：

@Override
protected RFuture<Boolean> unlockInnerAsync(long threadId) {
    String timeoutPrefix = getReadWriteTimeoutNamePrefix(threadId);
    String keyPrefix = getKeyPrefix(threadId, timeoutPrefix);

    return evalWriteAsync(getName(), LongCodec.INSTANCE, RedisCommands.EVAL_BOOLEAN,
            "local mode = redis.call('hget', KEYS[1], 'mode'); " +
            "if (mode == false) then " +
                "redis.call('publish', KEYS[2], ARGV[1]); " +
                "return 1; " +
            "end; " +
            "local lockExists = redis.call('hexists', KEYS[1], ARGV[2]); " +
            "if (lockExists == 0) then " +
                "return nil;" +
            "end; " +

            "local counter = redis.call('hincrby', KEYS[1], ARGV[2], -1); " + 
            "if (counter == 0) then " +
                "redis.call('hdel', KEYS[1], ARGV[2]); " + 
            "end;" +
            "redis.call('del', KEYS[3] .. ':' .. (counter+1)); " +

            "if (redis.call('hlen', KEYS[1]) > 1) then " +
                "local maxRemainTime = -3; " + 
                "local keys = redis.call('hkeys', KEYS[1]); " + 
                "for n, key in ipairs(keys) do " + 
                    "counter = tonumber(redis.call('hget', KEYS[1], key)); " + 
                    "if type(counter) == 'number' then " + 
                        "for i=counter, 1, -1 do " + 
                            "local remainTime = redis.call('pttl', KEYS[4] .. ':' .. key .. ':rwlock_timeout:' .. i); " + 
                            "maxRemainTime = math.max(remainTime, maxRemainTime);" + 
                        "end; " + 
                    "end; " + 
                "end; " +

                "if maxRemainTime > 0 then " +
                    "redis.call('pexpire', KEYS[1], maxRemainTime); " +
                    "return 0; " +
                "end;" + 

                "if mode == 'write' then " + 
                    "return 0;" + 
                "end; " +
            "end; " +

            "redis.call('del', KEYS[1]); " +
            "redis.call('publish', KEYS[2], ARGV[1]); " +
            "return 1; ",
            Arrays.<Object>asList(getName(), getChannelName(), timeoutPrefix, keyPrefix), 
            LockPubSub.UNLOCK_MESSAGE, getLockName(threadId));
}

我们可以看到，这读锁释放锁的lua脚本还是比较长的，但是我们也不用着急，一步一步分析就可以了。

1.1、KEYS

Arrays.