刚接手一个小站点，排队下单业务，由于普通时间业务量不大，在抢购活动（1000套）进行时，遇到数据库读取瓶颈。如下是一种轻便解决方案思路，有不足的大神指点一二。

说明：通过全局变量，限制下单数量和排队数量，在队列未消化前，让客户端等待下次发起

--全局变量，卡单，订单限制

/**
 * Created by lala on 2022/6/8.
 */
public  class Tools {
    //全局变量,当前出单数量
    public static int out_count = 0;
    //最大的处理量
    public volatile static int maxtodo=0;
}

--创建线程池，模拟多线程下单

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
 * Created by lala on 2022/6/8.
 */
public class MultiThread {

    //线程池
    ExecutorService executorService = Executors.newCachedThreadPool();

    public void testorder(){
        ThreadService threadService = new ThreadService();
        //线程池操作
        executorService.submit(()->threadService.order());
        executorService.submit(()->threadService.order());
        executorService.submit(()->threadService.order());
        executorService.submit(()->threadService.order());
    }
}

--下单业务
/**

• Created by lala on 2022/6/8.
  */

public class ThreadService {
    static ThreadService instance = new ThreadService();
    public void order() {
        //当前线程执行数量
        int docount = 0;
        //当最订单不满足接着循环
        while (Tools.out_count<1000){
            synchronized (instance) {
                //再次校验
                if (Tools.out_count >=1000) {
                    break;
                }
                //最大排队数量
                if(Tools.maxtodo>=10){
                    //通知客户端等待，结束当前http请求
                    continue;
                }
                //开始执行新的订单,maxtodo+1
                Tools.maxtodo++;
                docount++;
                try {
                    //执行的时间
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                //执行完总数量+一单
                Tools.out_count++;
                //执行结束当前排队减1
                Tools.maxtodo--;
            }
        }
        System.out.println("线程：" + Thread.currentThread().getName() + "出单了：" + docount + ", 总出单=" + Tools.out_count);
    }
}

--测试方法

public class test {
    public static void main(String[] args) {
        MultiThread multiThread = new MultiThread();
        multiThread.testorder();
        multiThread.executorService.shutdown();
    }
}