- 獲取鎖（unique_value可以是UUID等）
SET resource_name unique_value NX PX 30000

- 釋放鎖（lua腳本中，一定要比較value，防止誤解鎖）
if redis.call("get",KEYS[1]) == ARGV[1] then
    return redis.call("del",KEYS[1])
else
    return 0
end

<!-- https://mvnrepository.com/artifact/org.redisson/redisson -->
<dependency>
    <groupId>org.redisson</groupId>
    <artifactId>redisson</artifactId>
    <version>3.3.2</version>
</dependency>

Config config = new Config();
config.useSentinelServers().addSentinelAddress("127.0.0.1:6369","127.0.0.1:6379", "127.0.0.1:6389")
        .setMasterName("masterName")
        .setPassword("password").setDatabase(0);
RedissonClient redissonClient = Redisson.create(config);
// 還可以getFairLock(), getReadWriteLock()
RLock redLock = redissonClient.getLock("REDLOCK_KEY");
boolean isLock;
try {
    isLock = redLock.tryLock();
    // 500ms拿不到鎖, 就認(rèn)為獲取鎖失敗。10000ms即10s是鎖失效時(shí)間。
    isLock = redLock.tryLock(500, 10000, TimeUnit.MILLISECONDS);
    if (isLock) {
        //TODO if get lock success, do something;
    }
} catch (Exception e) {
} finally {
    // 無論如何, 最后都要解鎖
    redLock.unlock();
}

protected final UUID id = UUID.randomUUID();
String getLockName(long threadId) {
    return id + ":" + threadId;
}

<T> RFuture<T> tryLockInnerAsync(long leaseTime, TimeUnit unit, long threadId, RedisStrictCommand<T> command) {
    internalLockLeaseTime = unit.toMillis(leaseTime);
    // 獲取鎖時(shí)向5個(gè)redis實(shí)例發(fā)送的命令
    return commandExecutor.evalWriteAsync(getName(), LongCodec.INSTANCE, command,
              // 首先分布式鎖的KEY不能存在，如果確實(shí)不存在，那么執(zhí)行hset命令（hset REDLOCK_KEY uuid+threadId 1），并通過pexpire設(shè)置失效時(shí)間（也是鎖的租約時(shí)間）
              "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; " +
              // 如果分布式鎖的KEY已經(jīng)存在，并且value也匹配，表示是當(dāng)前線程持有的鎖，那么重入次數(shù)加1，并且設(shè)置失效時(shí)間
              "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; " +
              // 獲取分布式鎖的KEY的失效時(shí)間毫秒數(shù)
              "return redis.call('pttl', KEYS[1]);",
              // 這三個(gè)參數(shù)分別對(duì)應(yīng)KEYS[1]，ARGV[1]和ARGV[2]
                Collections.<Object>singletonList(getName()), internalLockLeaseTime, getLockName(threadId));
}

protected RFuture<Boolean> unlockInnerAsync(long threadId) {
    // 向5個(gè)redis實(shí)例都執(zhí)行如下命令
    return commandExecutor.evalWriteAsync(getName(), LongCodec.INSTANCE, RedisCommands.EVAL_BOOLEAN,
            // 如果分布式鎖KEY不存在，那么向channel發(fā)布一條消息
            "if (redis.call('exists', KEYS[1]) == 0) then " +
                "redis.call('publish', KEYS[2], ARGV[1]); " +
                "return 1; " +
            "end;" +
            // 如果分布式鎖存在，但是value不匹配，表示鎖已經(jīng)被占用，那么直接返回
            "if (redis.call('hexists', KEYS[1], ARGV[3]) == 0) then " +
                "return nil;" +
            "end; " +
            // 如果就是當(dāng)前線程占有分布式鎖，那么將重入次數(shù)減1
            "local counter = redis.call('hincrby', KEYS[1], ARGV[3], -1); " +
            // 重入次數(shù)減1后的值如果大于0，表示分布式鎖有重入過，那么只設(shè)置失效時(shí)間，還不能刪除
            "if (counter > 0) then " +
                "redis.call('pexpire', KEYS[1], ARGV[2]); " +
                "return 0; " +
            "else " +
                // 重入次數(shù)減1后的值如果為0，表示分布式鎖只獲取過1次，那么刪除這個(gè)KEY，并發(fā)布解鎖消息
                "redis.call('del', KEYS[1]); " +
                "redis.call('publish', KEYS[2], ARGV[1]); " +
                "return 1; "+
            "end; " +
            "return nil;",
            // 這5個(gè)參數(shù)分別對(duì)應(yīng)KEYS[1]，KEYS[2]，ARGV[1]，ARGV[2]和ARGV[3]
            Arrays.<Object>asList(getName(), getChannelName()), LockPubSub.unlockMessage, internalLockLeaseTime, getLockName(threadId));

}