限流，單機，分布式限流

總結：解決網站的高訪問量，有三大利器，緩存，降級，限流，我這里講解一下 常用的幾種限流手段。

          單機 ，有型號量，令牌通，漏桶，

          分布式，可以考慮從網關，redis ngnix, 阿里 Sentinel 等手段解決 。話不多說代碼如下：

      1.單機：

        1.1 型號量

    // 線程池

ExecutorService exec = Executors.newCachedThreadPool();
// 只能5個線程同時訪問
final Semaphore semp = new Semaphore(5);

@Override
public void limit() {
    // 模擬20個客戶端訪問
    for (int index = 0; index < 20; index++) {
        final int NO = index;
        Runnable run = new Runnable() {
            public void run() {
                try {
                    // 獲取許可 一直阻塞
                    semp.acquire();
                   // semp.tryAcquire(1, TimeUnit.MINUTES); //這個嘗試 多長時間獲取 到
                    //處理業務
                    log.info("Accessing: " + NO);
                    Thread.sleep((long) (Math.random() * 10000));
                    log.info("存在多少有效" + semp.availablePermits());
                } catch (InterruptedException e) {
                    log.info("error:{}",e);
                } finally {
                    // 訪問完后，釋放
                    semp.release();
                }
            }
        };
        exec.execute(run);
    }
    // 退出線程池
    //exec.shutdown();
}


1.2 guava

ExecutorService exec = Executors.newCachedThreadPool();// 線程池
final RateLimiter limit = RateLimiter.create(2);//1s只能有10個

@Override
public void limit() {
    // 模擬20個客戶端訪問
    for (int index = 0; index < 20; index++) {
        final int NO = index;
        Runnable run = new Runnable() {
            public void run() {
                try {
                    // 獲取許可
                    limit.acquire();
                    //處理業務
                    log.info("Accessing: " + NO);
                    Thread.sleep((long) (Math.random() * 10000));
                } catch (InterruptedException e) {
                    log.info("error:{}", e);
                }
            }
        };
        exec.submit(run);
    }
}

2.0 分布式版本 

  2.1  redis-spring-data

@Autowired
private RedisTemplate redisTemplate;
ExecutorService exec = Executors.newCachedThreadPool();// 線程池
@Override
public void limit() {
    //這里我用 包名+類名+方法
    String key = "com.example.demo.limit.redis.ResdisLimitServiceImpl.limit";

    RedisAtomicLong counter = new RedisAtomicLong(key, redisTemplate.getConnectionFactory());
    for (int i = 0; i < 100; i++) {
        final int no = i;
        exec.submit(new Runnable() {
            @Override
            public void run() {
                if (counter.incrementAndGet() > 10) {
                    //拒絕請求
                    log.info("拒絕請求{}", no);
                }
                try {
                    //處理請求
                    log.info("處理請求{}", no);
                } finally {
                    counter.decrementAndGet();
                }
                try {
                    Thread.sleep((long) (Math.random() * 10000));
                } catch (InterruptedException e) {

                }
            }
        });
    }
}

2.2 redission 版本

@Autowired
private RedissonClient redisson;

ExecutorService exec = Executors.newCachedThreadPool();// 線程池

@Override
public void limit() {
    RSemaphore semaphore = redisson.getSemaphore("semaphore");
    semaphore.trySetPermits(10);
    log.info("有效：{}",semaphore.availablePermits());
    for (int i = 0; i <100 ; i++) {
        final int no = i;
        exec.submit(new Runnable() {
            @Override
            public void run() {
                try {
                    if(semaphore.tryAcquire(1, TimeUnit.SECONDS)){
                        try {
                            log.info("處理業務{}",no);
                            Thread.sleep((long) (Math.random() * 10000));
                        }finally {
                            semaphore.release(1);
                        }
                    }else {
                        log.info("拒絕業務{}",no);
                    }
                } catch (InterruptedException e) {
                    log.error("error:{}",e);
                }
            }
        });
    }
}

3.0 基於注解 redis開發 限流 使用方便

使用如下：

@Limit(key = "test", period = 100, count = 10)

@PostMapping("dept/update")
public ResponseResult updateDept(String name, Boolean leader, Integer id
                                , Double age, BigDecimal price, ResponseResultCode em){

    return ResponseResultFactory.success("添加成功");
}
jmeter 測試如下 具體實現 參考我的代碼庫