asp.net通过消息队列处理高并发请求(以抢小米手机为例)_实用技巧_

 CREATE TABLE [dbo].[product]( [id] [int] NOT NULL,--唯一主键 [name] [nvarchar](50) NULL,--产品名称 [status] [int] NULL ,--0未售出 1 售出 默认为0 [username] [nvarchar](50) NULL--下单用户 ) 

 insert into product(id,name,status,username) values(1,'小米手机',0,null)

 public ContentResult PlaceOrder(string userName) { using (RuanMou2020Entities db = new RuanMou2020Entities()) { var product = db.product.Where(p => p.status== 0).FirstOrDefault(); if (product.status == 1) { return Content("失败，产品已经被卖光"); } else { //模拟数据库慢造成并发问题 Thread.Sleep(5000); product.status = 1; product.username= userName; 　　　　　　　　　　　　　　db.SaveChanges(); 　　　　　　　　　　　　　　return Content("成功购买"); 　　　　　　　　　　　　 } 　　　　　　} 　　　　}

 private static object _lock = new object(); public ContentResult PlaceOrder(string userName) { using (RuanMou2020Entities db = new RuanMou2020Entities()) { lock (_lock) { var product = db.product.Where(p => p.status == 0).FirstOrDefault(); if (product.status == 1) { return Content("失败，产品已经被卖光"); } else { //模拟数据库慢造成并发问题 Thread.Sleep(5000); product.status = 1; product.username = userName; db.SaveChanges(); return Content("成功购买"); } } } }

 public class HomeController : Controller { /// 
 /// 接受订单提交（生产者) /// 
 ///  public ContentResult PlaceOrderQueen(string userName) { //直接将请求写入到订单队列 OrderConsumer.TicketOrders.Enqueue(userName); return Content("wait"); } /// 
 /// 查询订单结果 /// 
 ///  public ContentResult PlaceOrderQueenResult(string userName) { var rel = OrderConsumer.OrderResults.Where(p => p.userName == userName).FirstOrDefault(); if (rel == null) { return Content("还在排队中"); } else { return Content(rel.Result.ToString()); } } }

 /// 
 /// 订单的处理者（消费者） /// 
 public class OrderConsumer { /// 
 /// 订票的消息队列 /// 
 public static ConcurrentQueue TicketOrders = new ConcurrentQueue(); /// 
 /// 订单结果消息队列 /// 
 public static List OrderResults = new List(); /// 
 /// 订单处理 /// 
 public static void StartTicketTask() { string userName = null; while (true) { //如果没有订单任务就休息1秒钟 if (!TicketOrders.TryDequeue(out userName)) { Thread.Sleep(1000); continue; } //执行真实的业务逻辑（如插入数据库） bool rel = new TicketHelper().PlaceOrderDataBase(userName); //将执行结果写入结果集合 OrderResults.Add(new OrderResult() { Result = rel, userName = userName }); } } }

 /// 
 /// 订单业务的实际处理者 /// 
 public class TicketHelper { /// 
 /// 实际库存标识 /// 
 private bool hasStock = true; /// 
 /// 执行一个订单到数据库 /// 
 ///  public bool PlaceOrderDataBase(string userName) { //如果没有了库存，则直接返回false，防止频繁读库 if (!hasStock) { return hasStock; } using (RuanMou2020Entities db = new RuanMou2020Entities()) { var product = db.product.Where(p => p.status == 0).FirstOrDefault(); if (product == null) { hasStock = false; return false; } else { Thread.Sleep(10000);//模拟数据库的效率比较慢，执行插入时间比较久 product.status = 1; product.username = userName; db.SaveChanges(); return true; } } } } /// 
 /// 订单处理结果实体 /// 
 public class OrderResult { public string userName { get; set; } public bool Result { get; set; } } 

 protected void Application_Start() { AreaRegistration.RegisterAllAreas(); GlobalConfiguration.Configure(WebApiConfig.Register); FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters); RouteConfig.RegisterRoutes(RouteTable.Routes); BundleConfig.RegisterBundles(BundleTable.Bundles); //在Global的Application_Start事件里单独开启一个消费者线程 Task.Run(OrderConsumer.StartTicketTask); }

 public class ProductForSaleManager { /// 
 /// 待售商品队列 /// 
 public static ConcurrentQueue ProductsForSale = new ConcurrentQueue(); /// 
 /// 初始化待售商品队列 /// 
 public static void Init() { using (RuanMou2020Entities db = new RuanMou2020Entities()) { db.product.Where(p => p.status == 0).Select(p => p.id).ToList().ForEach(p => { ProductsForSale.Enqueue(p); }); } } } public class MvcApplication : System.Web.HttpApplication { protected void Application_Start() { AreaRegistration.RegisterAllAreas(); GlobalConfiguration.Configure(WebApiConfig.Register); FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters); RouteConfig.RegisterRoutes(RouteTable.Routes); BundleConfig.RegisterBundles(BundleTable.Bundles); //程序启动前，先初始化待售产品消息队列 ProductForSaleManager.Init(); } }

 public class OrderController : Controller { /// 
 /// 下订单 /// 
 /// 订单提交者 ///  public async Task PlaceOrder(string userName) { if (ProductForSaleManager.ProductsForSale.TryDequeue(out int pid)) { await new TicketHelper2().PlaceOrderDataBase(userName, pid); return Content($"下单成功，对应产品id为：{pid}"); } else { await Task.CompletedTask; return Content($"商品已经被抢光"); } } }

 /// 
 /// 订单业务的实际处理者 /// 
 public class TicketHelper2 { /// 
 /// 执行复杂的订单操作（如数据库） /// 
 /// 下单用户 /// 产品id ///  public async Task PlaceOrderDataBase(string userName, int pid) { using (RuanMou2020Entities db = new RuanMou2020Entities()) { var product = db.product.Where(p => p.id == pid).FirstOrDefault(); if (product != null) { product.status = 1; product.username = userName; await db.SaveChangesAsync(); } } } }