SETNX toilet_1 "occupied"  # 嘗試鎖門(mén)

SETNX toilet_1 "occupied"
EXPIRE toilet_1 30  # 30秒后自動(dòng)解鎖

SET toilet_1 "user_123" NX EX 30  # 原子操作：鎖門(mén)+設(shè)置30秒自動(dòng)開(kāi)鎖

// RedissonRedLock.tryLock()的核心邏輯
while (waitTimeRemaining > 0) {
    long start = System.nanoTime();
    
    // 嘗試從多數(shù)節(jié)點(diǎn)獲取鎖
    int acquiredLocks = tryAcquireMultipleLocks();
    
    if (acquiredLocks >= majority) {
        // 計(jì)算實(shí)際有效時(shí)間
        long elapsed = System.nanoTime() - start;
        long lockTime = leaseTime - TimeUnit.NANOSECONDS.toMillis(elapsed);
        
        if (lockTime > 0) {
            // 對(duì)所有成功節(jié)點(diǎn)設(shè)置統(tǒng)一過(guò)期時(shí)間
            scheduleLockExpiration(lockTime);
            return true;
        }
        // 超時(shí)則釋放已獲得的鎖
        releaseAcquiredLocks();
    }
    
    // 等待隨機(jī)時(shí)間后重試
    waitTimeRemaining -= calculateWaitTime();
}

// 獲取鎖時(shí)返回單調(diào)遞增的token
LockResult result = redLock.tryLockWithToken();
long token = result.getToken();

// 操作資源時(shí)驗(yàn)證token
if (resource.getCurrentToken() < token) {
    resource.write(data, token);
} else {
    throw new ConcurrentModificationException();
}

// 獲取鎖（默認(rèn)30秒看門(mén)狗時(shí)間）
RLock lock = redisson.getLock("order_lock");
lock.lock(); // 內(nèi)部啟動(dòng)看門(mén)狗線程

try {
    // 執(zhí)行業(yè)務(wù)邏輯（可能超過(guò)30秒）
    processOrder();
} finally {
    lock.unlock(); // 釋放時(shí)會(huì)停止看門(mén)狗
}

public void lock() {
    try {
        lockInterruptibly();
    } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
    }
}

public void lockInterruptibly() throws InterruptedException {
    // 嘗試獲取鎖，默認(rèn)leaseTime=30秒
    tryAcquireAsync(leaseTime, TimeUnit.MILLISECONDS).sync();
    
    // 啟動(dòng)看門(mén)狗線程
    scheduleExpirationRenewal();
}

protected void scheduleExpirationRenewal() {
    Thread renewalThread = new Thread(() -> {
        while (!Thread.currentThread().isInterrupted()) {
            // 每10秒（leaseTime/3）續(xù)期一次
            try {
                Thread.sleep(leaseTime / 3);
                
                // 通過(guò)Lua腳本續(xù)期
                String script = 
                    "if redis.call('hexists', KEYS[1], ARGV[2]) == 1 then " +
                    "return redis.call('pexpire', KEYS[1], ARGV[1]); " +
                    "else return 0; end";
                
                redis.eval(script, 
                    Collections.singletonList(getName()),
                    internalLockLeaseTime, getLockName(Thread.currentThread().getId()));
            } catch (InterruptedException e) {
                Thread.currentThread().interrupt();
            }
        }
    });
    renewalThread.start();
}

<!-- pom.xml -->
<dependency>
    <groupId>org.redisson</groupId>
    <artifactId>redisson</artifactId>
    <version>3.16.8</version>
</dependency>

public class RedisLockDemo {
    private static RedissonClient redisson;
    
    static {
        Config config = new Config();
        config.useSingleServer().setAddress("redis://127.0.0.1:6379");
        redisson = Redisson.create(config);
    }
}

public boolean lockSeat(String seatNumber, String userId) {
    // 獲取分布式鎖對(duì)象
    RLock lock = redisson.getLock("seat:" + seatNumber);
    
    try {
        // 嘗試加鎖，waitTime=0表示不等待，leaseTime=10分鐘自動(dòng)解鎖
        return lock.tryLock(0, 10, TimeUnit.MINUTES);
    } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
        return false;
    }
}

public void unlockSeat(String seatNumber, String userId) {
    RLock lock = redisson.getLock("seat:" + seatNumber);
    
    // 檢查是否還被當(dāng)前線程持有
    if (lock.isHeldByCurrentThread()) {
        lock.unlock();
    }
}

public boolean selectSeat(String seatNumber, String userId) {
    if (!lockSeat(seatNumber, userId)) {
        System.out.println(userId + " 搶座失敗，座位已被鎖定");
        return false;
    }
    
    try {
        System.out.println(userId + " 成功鎖定座位 " + seatNumber);
        // 模擬用戶支付流程
        boolean paid = mockPaymentProcess(userId);
        
        if (paid) {
            System.out.println(userId + " 支付成功，座位確認(rèn)");
            return true;
        } else {
            System.out.println(userId + " 支付超時(shí)，座位釋放");
            return false;
        }
    } finally {
        unlockSeat(seatNumber, userId);
    }
}

private boolean mockPaymentProcess(String userId) {
    // 模擬50%概率支付成功
    try {
        Thread.sleep(2000); // 模擬支付思考時(shí)間
    } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
    }
    return new Random().nextBoolean();
}

public boolean lockSeatWithRenewal(String seatNumber, String userId) {
    RLock lock = redisson.getLock("seat:" + seatNumber);
    
    try {
        // 獲取鎖，并設(shè)置看門(mén)狗自動(dòng)續(xù)期（默認(rèn)30秒）
        lock.lock();
        
        // 啟動(dòng)一個(gè)線程定期續(xù)期
        new Thread(() -> {
            while (!Thread.currentThread().isInterrupted()) {
                try {
                    Thread.sleep(5000); // 每5秒續(xù)期一次
                    lock.expire(10, TimeUnit.MINUTES); // 續(xù)期10分鐘
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            }
        }).start();
        
        return true;
    } catch (Exception e) {
        return false;
    }
}

public static void main(String[] args) {
    RedisLockDemo demo = new RedisLockDemo();
    
    // 模擬3個(gè)用戶同時(shí)搶5號(hào)座位
    new Thread(() -> demo.selectSeat("A05", "用戶1")).start();
    new Thread(() -> demo.selectSeat("A05", "用戶2")).start();
    new Thread(() -> demo.selectSeat("A05", "用戶3")).start();
}