Redisson分布式
参考链接：https://www.cnblogs.com/jklixin/p/13212864.html
官网连接：https://redisson.org
Redisson分布式
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();
