具有有界队列的Java线程池

Question

我使用java.util.concurrent的Executors类来创建一个固定的线程池运行请求处理程序的Web服务器:

static ExecutorService  newFixedThreadPool(int nThreads) 

而描述是:

创建一个线程池,该线程池重用一组在共享无界队列中运行的固定线程.

但是,我正在寻找线程池实现,它将执行完全相同的操作,除了有界队列.有这样的实施吗？或者我是否需要为固定线程池实现自己的包装器？

Answer 1

您想要做的是新建自己的ExecutorService,可能使用ThreadPoolExecutor.ThreadPoolExecutor有一个构造函数,它接受一个BlockingQueue并获得一个有界的队列,例如正确构造用于边界的ArrayBlockingQueue.您还可以包含RejectedExecutionHandler,以确定队列已满时要执行的操作,或者挂起对阻塞队列的引用并使用offer方法.

这是一个小例子:

BlockingQueue<Runnable> linkedBlockingDeque = new LinkedBlockingDeque<Runnable>(
    100);
ExecutorService executorService = new ThreadPoolExecutor(1, 10, 30,
    TimeUnit.SECONDS, linkedBlockingDeque,
    new ThreadPoolExecutor.CallerRunsPolicy());

Answer 2

创建一个ThreadPoolexecutor并在其中传递合适的BlockingQueue实现.例如,您可以在ThreadPoolExecutor构造函数中传入ArrayBlockingQueue以获得所需的效果.

Answer 3

我已经用信号量解决了这个问题，我用它来限制提交到ExecutorService.

例如：

int threadCount = 10;
ExecutorService consumerPool = Executors.newFixedThreadPool(threadCount);

// set the permit count greater than thread count so that we 
// build up a limited buffer of waiting consumers
Semaphore semaphore = new Semaphore(threadCount * 100); 

for (int i = 0; i < 1000000; ++i) {
    semaphore.acquire(); // this might block waiting for a permit 
    Runnable consumer = () -> {
       try {
          doSomeWork(i);
       } finally {
          semaphore.release(); // release a permit 
       }
    };
    consumerPool.submit(consumer);
}