Semaphore flow control semaphore

Semaphore Used as a flow control semaphore in rocketmq There are good examples in

Semaphore It can be used to control the number of threads accessing shared resources at the same time

SemaphoreReleaseOnlyOnce#release
adopt cas Promise to release only once

public void release() {
    
        if (this.semaphore != null) {
    
            if (this.released.compareAndSet(false, true)) {
    
                this.semaphore.release();
            }
        }
    }

Use tryAcquire Get permission to ,tryAcquire You can add timeout

boolean acquired = this.semaphoreAsync.tryAcquire(timeoutMillis, TimeUnit.MILLISECONDS);
        if (acquired) {
    
            final SemaphoreReleaseOnlyOnce once = new SemaphoreReleaseOnlyOnce(this.semaphoreAsync);
            long costTime = System.currentTimeMillis() - beginStartTime;
            if (timeoutMillis < costTime) {
    
                once.release();
                throw new RemotingTimeoutException("invokeAsyncImpl call timeout");
            }