Redisson分布式

本文主要是介绍Redisson分布式，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

参考链接：https://www.cnblogs.com/jklixin/p/13212864.html

官网连接：https://redisson.org

Redisson分布式

GitHub中文文档

概念：是一个在Redis的基础上实现的Java驻内存数据网格（In-Memory Data Grid）。它不仅提供了一系列的分布式的Java常用对象，还提供了许多分布式服务

引入依赖

<dependency>
    <groupId>org.redisson</groupId>
    <artifactId>redisson</artifactId>
    <version>3.13.1</version>
</dependency>

配置

@Configuration
public class MyRedissonConfig {

    @Bean(destroyMethod = "shutdown")
    public RedissonClient redissonClient() throws IOException{
        //1.配置连接
        Config config = new Config();
        config.useSingleServer()
                .setPassword("123456")
                //可以用"rediss://"来启用SSL连接
                .setAddress("redis://123.56.16.54:6379");
        //2.创建客户端
        RedissonClient redissonClient= Redisson.create(config);
        return redissonClient;
    }
}

分布式锁

1、可重入锁

@ResponseBody
    @GetMapping("/hello")
    public String hello() {

        //1、获取一把锁，只要锁的名字一样，就是同一把锁
        RLock lock = redisson.getLock(" my-lock ");
        //2、加锁
        lock.lock();//阻塞式等待。默认加的锁都是30s时间。
        //1)、锁的自动续期，如果业务超长，运行期间自动给锁续上新的30s。不用担心业务时间长，锁自动过期被用特
        //2)、加锁的业务只要运行完成，就不会给当前锁续期，即使不手动解锁，锁默认在30s以后自动删除。
        try{
            System.out.println("加锁成功，执行业务..." + Thread.currentThread().getId());
            Thread.sleep(30000);
        } catch (Exception e) {

        } finally {
//3、解锁将设解锁代码没有运行，redisson会不会出现死锁
            System.out.println("释放锁..." + Thread.currentThread().getId());
            lock.unlock();
        }
        return "hello";
    }

基于Redis的Redisson分布式可重入锁RLock Java对象实现了java.util.concurrent.locks.Lock接口

大家都知道，如果负责储存这个分布式锁的Redisson节点宕机以后，而且这个锁正好处于锁住的状态时，这个锁会出现锁死的状态。为了避免这种情况的发生，Redisson内部提供了一个监控锁的看门狗，它的作用是在Redisson实例被关闭前，不断的延长锁的有效期。默认情况下，看门狗的检查锁的超时时间是30秒钟，也可以通过修改Config.lockWatchdogTimeout来另行指定。

try {
            while (true) {
                ttl = tryAcquire(leaseTime, unit, threadId);
                // lock acquired
                if (ttl == null) {
                    break;
                }

                // waiting for message
                if (ttl >= 0) {
                    try {
                        future.getNow().getLatch().tryAcquire(ttl, TimeUnit.MILLISECONDS);
                    } catch (InterruptedException e) {
                        if (interruptibly) {
                            throw e;
                        }
                        future.getNow().getLatch().tryAcquire(ttl, TimeUnit.MILLISECONDS);
                    }
                } else {
                    if (interruptibly) {
                        future.getNow().getLatch().acquire();
                    } else {
                        future.getNow().getLatch().acquireUninterruptibly();
                    }
                }
            }
        } finally {
            unsubscribe(future, threadId);
        }

另外Redisson还通过加锁的方法提供了leaseTime的参数来指定加锁的时间。超过这个时间后锁便自动解开了。

// 加锁以后10秒钟自动解锁,不会续期
// 无需调用unlock方法手动解锁
lock.lock(10, TimeUnit.SECONDS);//10秒自动解锁，自动解锁时间一定要大于业务的执行时间。
//问题：Lock.Lock(10,TimeUnit.SECONDS);在锁时间到了以后，不会自动续期。
//1、如果我们传递了锁的超时时间，就发送给redis执行脚本，进行占锁，默认超时就是我们指定的时间
//2、如果我们未指定锁的超时时间，就使用30*1000（LockivatchdogTimeout看门狗的默认时间）
//只要占锁成功，就会启动一个定时任务（重新给看门狗定义过期时间，新的过期时间是默认的30s），每个10s自动续期到30s
// internalLockLeaseTime【看门狗时间】/3,10s后

// 尝试加锁，最多等待100秒，超出不等，上锁以后10秒自动解锁
boolean res = lock.tryLock(100, 10, TimeUnit.SECONDS);
if (res) {
   try {
     ...
   } finally {
       lock.unlock();
   }
}

2、公平锁

保证了当多个Redisson客户端线程同时请求加锁时，优先分配给先发出请求的线程。所有请求线程会在一个队列中排队，当某个线程出现宕机时，Redisson会等待5秒后继续下一个线程，也就是说如果前面有5个线程都处于等待状态，那么后面的线程会等待至少25秒。

RLock fairLock = redisson.getFairLock("anyLock");
// 最常见的使用方法
fairLock.lock();

// 10秒钟以后自动解锁
// 无需调用unlock方法手动解锁
fairLock.lock(10, TimeUnit.SECONDS);

// 尝试加锁，最多等待100秒，上锁以后10秒自动解锁
boolean res = fairLock.tryLock(100, 10, TimeUnit.SECONDS);
...
fairLock.unlock();

3、读写锁

分布式可重入读写锁允许同时有多个读锁和一个写锁处于加锁状态。

RReadWriteLock rwlock = redisson.getReadWriteLock("anyRWLock");
// 最常见的加锁使用方法
rwlock.readLock().lock();
// 或
rwlock.writeLock().lock();


// 10秒钟以后自动解锁
// 无需调用unlock方法手动解锁
rwlock.readLock().lock(10, TimeUnit.SECONDS);
// 或
rwlock.writeLock().lock(10, TimeUnit.SECONDS);

// 尝试加锁，最多等待100秒，上锁以后10秒自动解锁
boolean res = rwlock.readLock().tryLock(100, 10, TimeUnit.SECONDS);
// 或
boolean res = rwlock.writeLock().tryLock(100, 10, TimeUnit.SECONDS);
...
lock.unlock();

进行写操作之前不能有锁，进行读操作之前可以有读锁，不能有写锁

4、信号量

	@ResponseBody
    @GetMapping("/acquire")
    public String AcquireSemaphore(){
        RSemaphore semaphore = redisson.getSemaphore("semaphore");
        //需要获取几个信号量参数就写几，默认为1
        boolean b = semaphore.tryAcquire();
        if(b){
            //获取成功
            return "获取成功:信号量-1..."+"当前信号量"+semaphore.availablePermits();
        }else{
            return "获取失败：等待...."+"当前信号量"+semaphore.availablePermits();
        }
    }

    @ResponseBody
    @GetMapping("/release")
    public String releaseSemaphore(){
        RSemaphore semaphore = redisson.getSemaphore("semaphore");
        semaphore.release();//semaphore.release(4);表示一次性释放4个信号量
        return "释放成功:信号量+1......"+"当前信号量"+semaphore.availablePermits();
    }

5、闭锁

（CountDownLatch)

RCountDownLatch latch = redisson.getCountDownLatch("anyCountDownLatch");
latch.trySetCount(3);//redis中存在一个anyCountDownLatch=3，当其等于0时就闭锁
latch.await();


// 在其他线程或其他JVM里
RCountDownLatch latch = redisson.getCountDownLatch("anyCountDownLatch");
latch.countDown();//redis中的anyCountDownLatch减一

基于 Redis 的 Java 分布式可重入Lock对象，并实现Lock接口。

如果获取锁的 Redisson 实例崩溃，那么这种锁可能会在获取状态下永远挂起。为了避免这种 Redisson 维护锁看门狗，它会在锁持有者 Redisson 实例处于活动状态时延长锁的过期时间。默认情况下，锁定看门狗超时为 30 秒，可以通过Config.lockWatchdogTimeout设置进行更改。

Redisson 还允许leaseTime在获取锁时指定参数。在指定的时间间隔后锁定的锁将自动释放。

RLock对象的行为符合 Java Lock 规范。这意味着只有锁所有者线程才能解锁它，否则IllegalMonitorStateException会被抛出。否则考虑使用RSemaphore对象。

代码示例：

RLock lock = redisson.getLock("myLock");

// traditional lock method
lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
boolean res = lock.tryLock(100, 10, TimeUnit.SECONDS);
if (res) {
   try {
     ...
   } finally {
       lock.unlock();
   }
}

Async接口使用代码示例：

RLock lock = redisson.getLock("myLock");

RFuture<Void> lockFuture = lock.lockAsync();

// or acquire lock and automatically unlock it after 10 seconds
RFuture<Void> lockFuture = lock.lockAsync(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
RFuture<Boolean> lockFuture = lock.tryLockAsync(100, 10, TimeUnit.SECONDS);

lockFuture.whenComplete((res, exception) -> {

    // ...

    lock.unlockAsync();
});

Reactive接口使用代码示例：

RedissonReactiveClient redisson = redissonClient.reactive();
RLockReactive lock = redisson.getLock("myLock");

Mono<Void> lockMono = lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Mono<Void> lockMono = lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Mono<Boolean> lockMono = lock.tryLock(100, 10, TimeUnit.SECONDS);

lockMono.doOnNext(res -> {
   // ...
})
.doFinally(lock.unlock())
.subscribe();

RxJava3接口使用代码示例：

RedissonRxClient redisson = redissonClient.rxJava();
RLockRx lock = redisson.getLock("myLock");

Completable lockRes = lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Completable lockRes = lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Single<Boolean> lockRes = lock.tryLock(100, 10, TimeUnit.SECONDS);

lockRes.doOnSuccess(res -> {
   // ...
})
.doFinally(lock.unlock())
.subscribe();

8.2. 公平锁

基于 Redis 的 Java 分布式可重入公平Lock对象实现了Lock接口。

公平锁保证线程将按照他们请求的顺序获取它。所有等待的线程都排队，如果某个线程已经死亡，那么 Redisson 等待它的返回 5 秒。例如，如果 5 个线程由于某种原因死亡，则延迟将是 25 秒。

如果获取锁的 Redisson 实例崩溃，那么这种锁可能会在获取状态下永远挂起。为了避免这种 Redisson 维护锁看门狗，它会在锁持有者 Redisson 实例处于活动状态时延长锁的过期时间。默认情况下，锁定看门狗超时为 30 秒，可以通过Config.lockWatchdogTimeout设置进行更改。

Redisson 还允许leaseTime在获取锁时指定参数。在指定的时间间隔后锁定的锁将自动释放。

RLock对象的行为符合 Java Lock 规范。这意味着只有锁所有者线程才能解锁它，否则IllegalMonitorStateException会被抛出。否则考虑使用RSemaphore对象。

代码示例：

RLock lock = redisson.getFairLock("myLock");

// traditional lock method
lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
boolean res = lock.tryLock(100, 10, TimeUnit.SECONDS);
if (res) {
   try {
     ...
   } finally {
       lock.unlock();
   }
}

Async接口使用代码示例：

RLock lock = redisson.getFairLock("myLock");

RFuture<Void> lockFuture = lock.lockAsync();

// or acquire lock and automatically unlock it after 10 seconds
RFuture<Void> lockFuture = lock.lockAsync(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
RFuture<Boolean> lockFuture = lock.tryLockAsync(100, 10, TimeUnit.SECONDS);

lockFuture.whenComplete((res, exception) -> {
    // ...
    lock.unlockAsync();
});

Reactive接口使用代码示例：

RedissonReactiveClient redisson = redissonClient.reactive();
RLockReactive lock = redisson.getFairLock("myLock");

Mono<Void> lockMono = lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Mono<Void> lockMono = lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Mono<Boolean> lockMono = lock.tryLock(100, 10, TimeUnit.SECONDS);

lockMono.doOnNext(res -> {
   // ...
})
.doFinally(lock.unlock())
.subscribe();

RxJava3接口使用代码示例：

RedissonRxClient redisson = redissonClient.rxJava();
RLockRx lock = redisson.getFairLock("myLock");

Completable lockRes = lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Completable lockRes = lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Single<Boolean> lockRes = lock.tryLock(100, 10, TimeUnit.SECONDS);

lockRes.doOnSuccess(res -> {
   // ...
})
.doFinally(lock.unlock())
.subscribe();

8.3. 多锁

基于 Redis 的分布式MultiLock对象允许对Lock对象进行分组并将它们作为单个锁处理。每个RLock对象可能属于不同的 Redisson 实例。

如果获取的 Redisson 实例MultiLock崩溃，那么这样的实例MultiLock可能会永远挂在获取状态。为了避免这种 Redisson 维护锁看门狗，它会在锁持有者 Redisson 实例处于活动状态时延长锁的过期时间。默认情况下，锁定看门狗超时为 30 秒，可以通过Config.lockWatchdogTimeout设置进行更改。

Redisson 还允许leaseTime在获取锁时指定参数。在指定的时间间隔后锁定的锁将自动释放。

MultiLock对象的行为符合 Java Lock 规范。这意味着只有锁所有者线程才能解锁它，否则IllegalMonitorStateException会被抛出。否则考虑使用RSemaphore对象。

代码示例：

RLock lock1 = redisson1.getLock("lock1");
RLock lock2 = redisson2.getLock("lock2");
RLock lock3 = redisson3.getLock("lock3");

RLock multiLock = anyRedisson.getMultiLock(lock1, lock2, lock3);

// traditional lock method
multiLock.lock();

// or acquire lock and automatically unlock it after 10 seconds
multiLock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
boolean res = multiLock.tryLock(100, 10, TimeUnit.SECONDS);
if (res) {
   try {
     ...
   } finally {
       multiLock.unlock();
   }
}

Async接口使用代码示例：

RLock lock1 = redisson1.getLock("lock1");
RLock lock2 = redisson2.getLock("lock2");
RLock lock3 = redisson3.getLock("lock3");

RLock multiLock = anyRedisson.getMultiLock(lock1, lock2, lock3);

RFuture<Void> lockFuture = multiLock.lockAsync();

// or acquire lock and automatically unlock it after 10 seconds
RFuture<Void> lockFuture = multiLock.lockAsync(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
RFuture<Boolean> lockFuture = multiLock.tryLockAsync(100, 10, TimeUnit.SECONDS);

lockFuture.whenComplete((res, exception) -> {
    // ...
    multiLock.unlockAsync();
});

Reactive接口使用代码示例：

RedissonReactiveClient anyRedisson = redissonClient.reactive();

RLockReactive lock1 = redisson1.getLock("lock1");
RLockReactive lock2 = redisson2.getLock("lock2");
RLockReactive lock3 = redisson3.getLock("lock3");

RLockReactive multiLock = anyRedisson.getMultiLock(lock1, lock2, lock3);

Mono<Void> lockMono = multiLock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Mono<Void> lockMono = multiLock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Mono<Boolean> lockMono = multiLock.tryLock(100, 10, TimeUnit.SECONDS);

lockMono.doOnNext(res -> {
   // ...
})
.doFinally(multiLock.unlock())
.subscribe();

RxJava3接口使用代码示例：

RedissonRxClient anyRedisson = redissonClient.rxJava();

RLockRx lock1 = redisson1.getLock("lock1");
RLockRx lock2 = redisson2.getLock("lock2");
RLockRx lock3 = redisson3.getLock("lock3");

RLockRx multiLock = anyRedisson.getMultiLock(lock1, lock2, lock3);

Completable lockRes = multiLock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Completable lockRes = multiLock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Single<Boolean> lockRes = multiLock.tryLock(100, 10, TimeUnit.SECONDS);

lockRes.doOnSuccess(res -> {
   // ...
})
.doFinally(multiLock.unlock())
.subscribe();

8.4. 红锁

此对象已弃用。RLock 操作现在传播到所有 Redis 从站。

8.5。读写锁

基于 Redis 的 Java 分布式可重入ReadWriteLock对象实现了ReadWriteLock接口。读写锁都实现了 RLock接口。

允许多个 ReadLock 所有者和仅一个 WriteLock 所有者。

如果获取锁的 Redisson 实例崩溃，那么这种锁可能会在获取状态下永远挂起。为了避免这种 Redisson 维护锁看门狗，它会在锁持有者 Redisson 实例处于活动状态时延长锁的过期时间。默认情况下，锁定看门狗超时为 30 秒，可以通过Config.lockWatchdogTimeout设置进行更改。

Redisson 还允许leaseTime在获取锁时指定参数。在指定的时间间隔后锁定的锁将自动释放。

RLock对象的行为符合 Java Lock 规范。这意味着只有锁所有者线程才能解锁它，否则IllegalMonitorStateException会被抛出。否则考虑使用RSemaphore对象。

代码示例：

RReadWriteLock rwlock = redisson.getReadWriteLock("myLock");

RLock lock = rwlock.readLock();
// or
RLock lock = rwlock.writeLock();

// traditional lock method
lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
boolean res = lock.tryLock(100, 10, TimeUnit.SECONDS);
if (res) {
   try {
     ...
   } finally {
       lock.unlock();
   }
}

Async接口使用代码示例：

RReadWriteLock rwlock = redisson.getReadWriteLock("myLock");

RLock lock = rwlock.readLock();
// or
RLock lock = rwlock.writeLock();

RFuture<Void> lockFuture = lock.lockAsync();

// or acquire lock and automatically unlock it after 10 seconds
RFuture<Void> lockFuture = lock.lockAsync(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
RFuture<Boolean> lockFuture = lock.tryLockAsync(100, 10, TimeUnit.SECONDS);

lockFuture.whenComplete((res, exception) -> {

    // ...

    lock.unlockAsync();
});

Reactive接口使用代码示例：

RedissonReactiveClient redisson = redissonClient.reactive();

RReadWriteLockReactive rwlock = redisson.getReadWriteLock("myLock");

RLockReactive lock = rwlock.readLock();
// or
RLockReactive lock = rwlock.writeLock();

Mono<Void> lockMono = lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Mono<Void> lockMono = lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Mono<Boolean> lockMono = lock.tryLock(100, 10, TimeUnit.SECONDS);

lockMono.doOnNext(res -> {
   // ...
})
.doFinally(lock.unlock())
.subscribe();

RxJava3接口使用代码示例：

RedissonRxClient redisson = redissonClient.rxJava();

RReadWriteLockRx rwlock = redisson.getReadWriteLock("myLock");

RLockRx lock = rwlock.readLock();
// or
RLockRx lock = rwlock.writeLock();

Completable lockRes = lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Completable lockRes = lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Single<Boolean> lockRes = lock.tryLock(100, 10, TimeUnit.SECONDS);

lockRes.doOnSuccess(res -> {
   // ...
})
.doFinally(lock.unlock())
.subscribe();

8.6. 信号

基于 Redis 的 Java 分布式Semaphore对象，类似于Semaphore对象。

可以在使用前进行初始化，但这不是必需的，通过trySetPermits(permits)方法获得可用的许可数量。

代码示例：

RSemaphore semaphore = redisson.getSemaphore("mySemaphore");

// acquire single permit
semaphore.acquire();

// or acquire 10 permits
semaphore.acquire(10);

// or try to acquire permit
boolean res = semaphore.tryAcquire();

// or try to acquire permit or wait up to 15 seconds
boolean res = semaphore.tryAcquire(15, TimeUnit.SECONDS);

// or try to acquire 10 permit
boolean res = semaphore.tryAcquire(10);

// or try to acquire 10 permits or wait up to 15 seconds
boolean res = semaphore.tryAcquire(10, 15, TimeUnit.SECONDS);
if (res) {
   try {
     ...
   } finally {
       semaphore.release();
   }
}

Async接口使用代码示例：

RSemaphore semaphore = redisson.getSemaphore("mySemaphore");

// acquire single permit
RFuture<Void> acquireFuture = semaphore.acquireAsync();

// or acquire 10 permits
RFuture<Void> acquireFuture = semaphore.acquireAsync(10);

// or try to acquire permit
RFuture<Boolean> acquireFuture = semaphore.tryAcquireAsync();

// or try to acquire permit or wait up to 15 seconds
RFuture<Boolean> acquireFuture = semaphore.tryAcquireAsync(15, TimeUnit.SECONDS);

// or try to acquire 10 permit
RFuture<Boolean> acquireFuture = semaphore.tryAcquireAsync(10);

// or try to acquire 10 permits or wait up to 15 seconds
RFuture<Boolean> acquireFuture = semaphore.tryAcquireAsync(10, 15, TimeUnit.SECONDS);

acquireFuture.whenComplete((res, exception) -> {
    // ...
    semaphore.releaseAsync();
});

Reactive接口使用代码示例：

RedissonReactiveClient redisson = redissonClient.reactive();

RSemaphoreReactive semaphore = redisson.getSemaphore("mySemaphore");

// acquire single permit
Mono<Void> acquireMono = semaphore.acquire();

// or acquire 10 permits
Mono<Void> acquireMono = semaphore.acquire(10);

// or try to acquire permit
Mono<Boolean> acquireMono = semaphore.tryAcquire();

// or try to acquire permit or wait up to 15 seconds
Mono<Boolean> acquireMono = semaphore.tryAcquire(15, TimeUnit.SECONDS);

// or try to acquire 10 permit
Mono<Boolean> acquireMono = semaphore.tryAcquire(10);

// or try to acquire 10 permits or wait up to 15 seconds
Mono<Boolean> acquireMono = semaphore.tryAcquire(10, 15, TimeUnit.SECONDS);

acquireMono.doOnNext(res -> {
   // ...
})
.doFinally(semaphore.release())
.subscribe();

RxJava3接口使用代码示例：

RedissonRxClient redisson = redissonClient.rxJava();

RSemaphoreRx semaphore = redisson.getSemaphore("mySemaphore");

// acquire single permit
Completable acquireRx = semaphore.acquire();

// or acquire 10 permits
Completable acquireRx = semaphore.acquire(10);

// or try to acquire permit
Single<Boolean> acquireRx = semaphore.tryAcquire();

// or try to acquire permit or wait up to 15 seconds
Single<Boolean> acquireRx = semaphore.tryAcquire(15, TimeUnit.SECONDS);

// or try to acquire 10 permit
Single<Boolean> acquireRx = semaphore.tryAcquire(10);

// or try to acquire 10 permits or wait up to 15 seconds
Single<Boolean> acquireRx = semaphore.tryAcquire(10, 15, TimeUnit.SECONDS);

acquireRx.doOnSuccess(res -> {
   // ...
})
.doFinally(semaphore.release())
.subscribe();

8.7. PermitExpirableSemaphore

基于 Redis 的 Java 分布式信号量对象，为每个获得的许可提供租用时间参数支持。每个许可证都由自己的 ID 标识，并且只能使用其 ID 释放。

应在使用前通过方法使用可用许可数量进行初始化trySetPermits(permits)。允许通过addPermits(permits)方法增加/减少可用许可证的数量。

代码示例：

RPermitExpirableSemaphore semaphore = redisson.getPermitExpirableSemaphore("mySemaphore");

semaphore.trySetPermits(23);

// acquire permit
String id = semaphore.acquire();

// or acquire permit with lease time in 10 seconds
String id = semaphore.acquire(10, TimeUnit.SECONDS);

// or try to acquire permit
String id = semaphore.tryAcquire();

// or try to acquire permit or wait up to 15 seconds
String id = semaphore.tryAcquire(15, TimeUnit.SECONDS);

// or try to acquire permit with least time 15 seconds or wait up to 10 seconds
String id = semaphore.tryAcquire(10, 15, TimeUnit.SECONDS);
if (id != null) {
   try {
     ...
   } finally {
       semaphore.release(id);
   }
}

Async接口使用代码示例：

RPermitExpirableSemaphore semaphore = redisson.getPermitExpirableSemaphore("mySemaphore");

RFuture<Boolean> setFuture = semaphore.trySetPermitsAsync(23);

// acquire permit
RFuture<String> acquireFuture = semaphore.acquireAsync();

// or acquire permit with lease time in 10 seconds
RFuture<String> acquireFuture = semaphore.acquireAsync(10, TimeUnit.SECONDS);

// or try to acquire permit
RFuture<String> acquireFuture = semaphore.tryAcquireAsync();

// or try to acquire permit or wait up to 15 seconds
RFuture<String> acquireFuture = semaphore.tryAcquireAsync(15, TimeUnit.SECONDS);

// or try to acquire permit with least time 15 seconds or wait up to 10 seconds
RFuture<String> acquireFuture = semaphore.tryAcquireAsync(10, 15, TimeUnit.SECONDS);
acquireFuture.whenComplete((id, exception) -> {
    // ...
    semaphore.releaseAsync(id);
});

Reactive接口使用代码示例：

RedissonReactiveClient redisson = redissonClient.reactive();

RPermitExpirableSemaphoreReactive semaphore = redisson.getPermitExpirableSemaphore("mySemaphore");

Mono<Boolean> setMono = semaphore.trySetPermits(23);

// acquire permit
Mono<String> acquireMono = semaphore.acquire();

// or acquire permit with lease time in 10 seconds
Mono<String> acquireMono = semaphore.acquire(10, TimeUnit.SECONDS);

// or try to acquire permit
Mono<String> acquireMono = semaphore.tryAcquire();

// or try to acquire permit or wait up to 15 seconds
Mono<String> acquireMono = semaphore.tryAcquire(15, TimeUnit.SECONDS);

// or try to acquire permit with least time 15 seconds or wait up to 10 seconds
Mono<String> acquireMono = semaphore.tryAcquire(10, 15, TimeUnit.SECONDS);

acquireMono.flatMap(id -> {
   // ...
   return semaphore.release(id);
}).subscribe();

RxJava3接口使用代码示例：

RedissonRxClient redisson = redissonClient.rxJava();

RPermitExpirableSemaphoreRx semaphore = redisson.getPermitExpirableSemaphore("mySemaphore");

Single<Boolean> setRx = semaphore.trySetPermits(23);

// acquire permit
Single<String> acquireRx = semaphore.acquire();

// or acquire permit with lease time in 10 seconds
Single<String> acquireRx = semaphore.acquire(10, TimeUnit.SECONDS);

// or try to acquire permit
Maybe<String> acquireRx = semaphore.tryAcquire();

// or try to acquire permit or wait up to 15 seconds
Maybe<String> acquireRx = semaphore.tryAcquire(15, TimeUnit.SECONDS);

// or try to acquire permit with least time 15 seconds or wait up to 10 seconds
Maybe<String> acquireRx = semaphore.tryAcquire(10, 15, TimeUnit.SECONDS);

acquireRx.flatMap(id -> {
   // ...
   return semaphore.release(id);
}).subscribe();

8.8. 倒计时锁存器

基于 Redis 的 Java 分布式CountDownLatch对象的结构类似于CountDownLatch对象。

应trySetCount(count)在使用前使用 count by method 进行初始化。

代码示例：

RCountDownLatch latch = redisson.getCountDownLatch("myCountDownLatch");

latch.trySetCount(1);
// await for count down
latch.await();

// in other thread or JVM
RCountDownLatch latch = redisson.getCountDownLatch("myCountDownLatch");
latch.countDown();

Async接口使用代码示例：

RCountDownLatch latch = redisson.getCountDownLatch("myCountDownLatch");

RFuture<Boolean> setFuture = lock.trySetCountAsync(1);
// await for count down
RFuture<Void> awaitFuture = latch.awaitAsync();

// in other thread or JVM
RCountDownLatch latch = redisson.getCountDownLatch("myCountDownLatch");
RFuture<Void> countFuture = latch.countDownAsync();

Reactive接口使用代码示例：

RedissonReactiveClient redisson = redissonClient.reactive();
RCountDownLatchReactive latch = redisson.getCountDownLatch("myCountDownLatch");

Mono<Boolean> setMono = latch.trySetCount(1);
// await for count down
Mono<Void> awaitMono = latch.await();

// in other thread or JVM
RCountDownLatchReactive latch = redisson.getCountDownLatch("myCountDownLatch");
Mono<Void> countMono = latch.countDown();

RxJava3接口使用代码示例：

RedissonRxClient redisson = redissonClient.rxJava();
RCountDownLatchRx latch = redisson.getCountDownLatch("myCountDownLatch");

Single<Boolean> setRx = latch.trySetCount(1);
// await for count down
Completable awaitRx = latch.await();

// in other thread or JVM
RCountDownLatchRx latch = redisson.getCountDownLatch("myCountDownLatch");
Completable countRx = latch.countDown();

8.9。自旋锁

基于 Redis 的 Java 分布式可重入SpinLock对象，并实现Lock接口。

由于Lock对象中的 pubsub 使用情况，每短时间间隔获取/释放数千个或更多锁可能会导致达到网络吞吐量限制和 Redis CPU 过载。这是由于 Redis pubsub 的性质而发生的 - 消息被分发到 Redis 集群中的所有节点。Spin Lock 默认使用指数退避策略来获取锁，而不是 pubsub 通道。

如果获取锁的 Redisson 实例崩溃，那么这种锁可能会在获取状态下永远挂起。为了避免这种 Redisson 维护锁看门狗，它会在锁持有者 Redisson 实例处于活动状态时延长锁的过期时间。默认情况下，锁定看门狗超时为 30 秒，可以通过Config.lockWatchdogTimeout设置进行更改。

Redisson 还允许leaseTime在获取锁时指定参数。在指定的时间间隔后锁定的锁将自动释放。

RLock对象的行为符合 Java Lock 规范。这意味着只有锁所有者线程才能解锁它，否则IllegalMonitorStateException会被抛出。否则考虑使用RSemaphore对象。

代码示例：

RLock lock = redisson.getSpinLock("myLock");

// traditional lock method
lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
boolean res = lock.tryLock(100, 10, TimeUnit.SECONDS);
if (res) {
   try {
     ...
   } finally {
       lock.unlock();
   }
}

Async接口使用代码示例：

RLock lock = redisson.getSpinLock("myLock");

RFuture<Void> lockFuture = lock.lockAsync();

// or acquire lock and automatically unlock it after 10 seconds
RFuture<Void> lockFuture = lock.lockAsync(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
RFuture<Boolean> lockFuture = lock.tryLockAsync(100, 10, TimeUnit.SECONDS);

lockFuture.whenComplete((res, exception) -> {

    // ...

    lock.unlockAsync();
});

Reactive接口使用代码示例：

RedissonReactiveClient redisson = redissonClient.reactive();
RLockReactive lock = redisson.getSpinLock("myLock");

Mono<Void> lockMono = lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Mono<Void> lockMono = lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Mono<Boolean> lockMono = lock.tryLock(100, 10, TimeUnit.SECONDS);

lockMono.doOnNext(res -> {
   // ...
})
.doFinally(lock.unlock())
.subscribe();

RxJava3接口使用代码示例：

RedissonRxClient redisson = redissonClient.rxJava();
RLockRx lock = redisson.getSpinLock("myLock");

Completable lockRes = lock.lock();

// or acquire lock and automatically unlock it after 10 seconds
Completable lockRes = lock.lock(10, TimeUnit.SECONDS);

// or wait for lock aquisition up to 100 seconds 
// and automatically unlock it after 10 seconds
Single<Boolean> lockRes = lock.tryLock(100, 10, TimeUnit.SECONDS);

lockRes.doOnSuccess(res -> {
   // ...
})
.doFinally(lock.unlock())
.subscribe();

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