Redisson分布式锁学习总结：写锁 RedissonWriteLock#unLock 释放锁源码分析

1、RedissonWriteLock 之 lua 脚本释放锁

关于 RedissonWriteLock 释放锁的源码，我们这里也是不再做分析了，因为 RedissonWriteLock 也是基于 RedissonLock 做的扩展，所以释放锁的源码也是和 RedissonLock 保持一致的，我们这里只需要分析 lua 脚本是如何执行即可。

分析前，我们定一下加锁的key：

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

RedissonWriteLock#unlockInnerAsync：

@Override
protected RFuture<Boolean> unlockInnerAsync(long threadId) {
    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;" +
            "if (mode == 'write') then " +
                "local lockExists = redis.call('hexists', KEYS[1], ARGV[3]); " +
                "if (lockExists == 0) then " +
                    "return nil;" +
                "else " +
                    "local counter = redis.call('hincrby', KEYS[1], ARGV[3], -1); " +
                    "if (counter > 0) then " +
                        "redis.call('pexpire', KEYS[1], ARGV[2]); " +
                        "return 0; " +
                    "else " +
                        "redis.call('hdel', KEYS[1], ARGV[3]); " +
                        "if (redis.call('hlen', KEYS[1]) == 1) then " +
                            "redis.call('del', KEYS[1]); " +
                            "redis.call('publish', KEYS[2], ARGV[1]); " + 
                        "else " +
                            // has unlocked read-locks
                            "redis.call('hset', KEYS[1], 'mode', 'read'); " +
                        "end; " +
                        "return 1; "+
                    "end; " +
                "end; " +
            "end; "
            + "return nil;",
    Arrays.<Object>asList(getName(), getChannelName()), 
    LockPubSub.READ_UNLOCK_MESSAGE, internalLockLeaseTime, getLockName(threadId));
}

我们可以看到，这读锁释放锁的lua脚本不算长，一步一步分析就可以了。

1.1、KEYS

Arrays.