并发实战题（一）

实现一个流控程序。控制客户端每秒调用某个远程服务不超过N次，客户端是会多线程并发调用，需要一个轻量简洁的实现，大家看看下面的一个实现，然后可以自己写一个实现。

import java.util.Date; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Semaphore; import java.util.concurrent.TimeUnit; public class Test { final static int MAX_QPS = 10; final static Semaphore semaphore = new Semaphore(MAX_QPS); public static void main (String ... args) throws Exception { Executors.newScheduledThreadPool(1).scheduleAtFixedRate(new Runnable() { @Override public void run() { semaphore.release(MAX_QPS/2); } }, 1000, 500, TimeUnit.MILLISECONDS); //lots of concurrent calls:100 * 1000 ExecutorService pool = Executors.newFixedThreadPool(100); for (int i=100;i>0;i--) { final int x = i; pool.submit(new Runnable() { @Override public void run() { for (int j=1000;j>0;j--) { semaphore.acquireUninterruptibly(1); remoteCall(x, j); } } }); } pool.shutdown(); pool.awaitTermination(1, TimeUnit.HOURS); System.out.println("DONE"); } private static void remoteCall(int i, int j) { System.out.println(String.format("%s - %s: %d %d",new Date(), Thread.currentThread(), i, j)); } }

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