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Wismyluckstar

opened on May 25, 2020

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1. lkqm commented on May 31, 2020

   

   lkqm

   on May 31, 2020

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   目前确实会存在这样的问题, 后续使用lock.tryLock修复这个问题
2. lkqm

   added a commit that references this issue on May 31, 2020

   Fix binarywang#1582 use lock.tryLock() avoid waiting for locks for a …

   This issue will close once commit 829b103 is merged into the 'master' branch.

   829b103
3. binarywang

   added a commit that references this issue on May 31, 2020

   🐛 #1582 use lock.tryLock() to avoid waiting for locks for a long time

   6c3d090
4. binarywang commented on Jul 19, 2020

   

   binarywang

   on Jul 19, 2020

   Owner

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   已修复
5. binarywang

   closed this as completedon Jul 19, 2020
6. cookier commented on Sep 16, 2020

   

   cookier

   on Sep 16, 2020

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   请问一下把lock改成tryLock有什么提升吗？
   因为我看这里tryLock也是通过不断循环，判断是否锁住，跟lock直接锁住好像效果一样？
7. lkqm commented on Sep 16, 2020

   

   lkqm

   on Sep 16, 2020

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   如果用lock这里有上万个请求会导致最后一个请求会等待前面9999个人的时间。而实际上只希望请求tencent获取accessToen只有一个线程，而使用tryLock会在某个线程更新accessToken后，其余线程只需要短暂等待后即可获取有效的accessToekn.
8. cookier commented on Sep 17, 2020

   

   cookier

   on Sep 17, 2020

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   在做测试之前，看你的说明后我理解是lock为单纯阻塞，并发线程都在干等着；tryLock则保持了并发线程的灵活性，只需要短暂等待就能拿到结果。不过再仔细想，每个线程都要额外等多100毫秒，响应不是更慢吗？
   模拟并发测试后发现lock方式执行时间1000+。tryLock执行时间3000+，不知道我测试方式是否正确。

       private Lock lock = new ReentrantLock();
       static boolean flag = false;
       static long x = System.currentTimeMillis();
   
       @Test
       public void testLock() throws IOException {
           for (int i = 0; i < 1000; i++) {
               new Thread(() -> doSome()).start();
           }
           System.in.read();
       }
   
       public void doSome() {
           lock.lock();
           try {
               if (flag) {
                   return;
               }
               System.out.println(Thread.currentThread().getName() + "得到了锁" + DateUtil.format(new Date(), "yyyy-MM-dd HH:mm:ss:SSS"));
               //模拟耗时操作
               Thread.sleep(1000);
               flag = true;
           } catch (Exception e) {
               e.printStackTrace();
           } finally {
               lock.unlock();
               System.out.println(System.currentTimeMillis() - x);
           }
       }
   
       public void doSome2() {
           boolean locked = false;
           try {
               do {
                   locked = lock.tryLock(100,TimeUnit.MICROSECONDS);
                   if (flag) {
                       return;
                   }
               } while (!locked);
   
               System.out.println(Thread.currentThread().getName() + "得到了锁" + DateUtil.format(new Date(), "yyyy-MM-dd HH:mm:ss:SSS"));
               //模拟耗时操作
               Thread.sleep(1000);
               flag = true;
           } catch (Exception e) {
               e.printStackTrace();
           } finally {
               if (locked) {
                   lock.unlock();
               }
               System.out.println(System.currentTimeMillis() - x);
           }
       }

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