并发实战题（一）

最新推荐文章于 2023-10-14 15:27:13 发布

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最新推荐文章于 2023-10-14 15:27:13 发布

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文章标签： java

原文链接：https://yq.aliyun.com/articles/26369

作者：一粟

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。

 
    01 import java.util.Date; 

    02 

    03 import java.util.concurrent.ExecutorService; 

    04 

    05 import java.util.concurrent.Executors; 

    06 

    07 import java.util.concurrent.Semaphore; 

    08 

    09 import java.util.concurrent.TimeUnit; 

    10 

    11 public class Test { 

    12 

    13     final static int MAX_QPS = 10; 

    14 

    15     final static Semaphore semaphore = new Semaphore(MAX_QPS); 

    16 

    17     public static void main (String ... args) throws Exception { 

    18 

    19         Executors.newScheduledThreadPool(1).scheduleAtFixedRate(new Runnable() { 

    20 

    21             @Override 

    22 

    23             public void run() { 

    24 

    25                 semaphore.release(MAX_QPS/2); 

    26 

    27             } 

    28 

    29         }, 1000, 500, TimeUnit.MILLISECONDS); 

    30 

    31         //lots of concurrent calls:100 * 1000 

    32         ExecutorService pool = Executors.newFixedThreadPool(100); 

    33 

    34         for (int i=100;i>0;i--) { 

    35 

    36             final int x = i; 

    37 

    38             pool.submit(new Runnable() { 

    39 

    40                 @Override 

    41 

    42                 public void run() { 

    43 

    44                     for (int j=1000;j>0;j--) { 

    45 

    46                         semaphore.acquireUninterruptibly(1); 

    47                         remoteCall(x, j); 

    48 

    49                     } 

    50 

    51                 } 

    52 

    53             }); 

    54 

    55         } 

    56 

    57         pool.shutdown(); 

    58 

    59         pool.awaitTermination(1, TimeUnit.HOURS); 

    60 

    61         System.out.println("DONE"); 

    62     } 

    63 

    64     private static void remoteCall(int i, int j) { 

    65         System.out.println(String.format("%s - %s: %d %d",new Date(), 

    66             Thread.currentThread(), i, j)); 

    67     } 

    68 

    69}