Redisson readWriteLock

Redisson readWriteLock 其实是通过两个类：

1. RedissonReadLock
2. RedissonWriteLock

核心代码就是这两个类里面的script，如readlock的获取读锁如下

return commandExecutor.evalWriteAsync(getName(), LongCodec.INSTANCE, command,
"local mode = redis.call('hget', KEYS[1], 'mode'); " +
//锁不存在
"if (mode == false) then " +
//设置hash内容
"redis.call('hset', KEYS[1], 'mode', 'read'); " +
"redis.call('hset', KEYS[1], ARGV[2], 1); " +
//设置一个{lock}:6ebc68ab-79ce-42d7-9c7d-00401fab055e:1:rwlock_timeout:1 对象，注意结尾是：1
"redis.call('set', KEYS[2] .. ':1', 1); " +
"redis.call('pexpire', KEYS[2] .. ':1', ARGV[1]); " +
"redis.call('pexpire', KEYS[1], ARGV[1]); " +
"return nil; " +
"end; " +
"if (mode == 'read') or (mode == 'write' and redis.call('hexists', KEYS[1], ARGV[3]) == 1) then " +
//如果当前是读锁，或者写锁也是由当前线程获得
"local ind = redis.call('hincrby', KEYS[1], ARGV[2], 1); " +
"local key = KEYS[2] .. ':' .. ind;" +
"redis.call('set', key, 1); " +
"redis.call('pexpire', key, ARGV[1]); " +
"local remainTime = redis.call('pttl', KEYS[1]); " +
"redis.call('pexpire', KEYS[1], math.max(remainTime, ARGV[1])); " +
"return nil; " +
"end;" +
"return redis.call('pttl', KEYS[1]);",
Arrays.<Object>asList(getName(), getReadWriteTimeoutNamePrefix(threadId)),
internalLockLeaseTime, getLockName(threadId), getWriteLockName(threadId));

可以看到几点：

1. 以hash模式存放
2. 整个hash设置了过期时间，即会自动释放锁
3. 锁也设置了过期时间