你可能写了个假异步,并不能提高请求线程池的吞吐量

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所属分类:.NET技术
摘要

不知道用什么词形容,就叫它假异步吧。写异步方法,async 和 await 要一路写到底,否则就是假异步,并不能提高请求线程池的吞吐量。

不知道用什么词形容,就叫它假异步吧。

写异步方法,async 和 await 要一路写到底,否则就是假异步,并不能提高请求线程池的吞吐量。

真正的异步,我的理解是这样的:比如调用一个查询接口,在当前线程,把SQL扔给数据库,当前线程释放,去干别的事情,数据库查询完了,通知我,我再在另一个线程里(也可能是刚才释放的那个线程,也可能不是)拿查询结果,返回给客户端,数据库查询比较耗时,数据库查询的时候,对线程是0占用。

 
HttpUtil.HttpGet方法:
你可能写了个假异步,并不能提高请求线程池的吞吐量你可能写了个假异步,并不能提高请求线程池的吞吐量

/// <summary> /// HttpGet /// </summary> /// <param name="url">url路径名称</param> /// <param name="cookie">cookie</param> public static string HttpGet(string url, CookieContainer cookie = null, WebHeaderCollection headers = null) {     try     {         // 设置参数         HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;         request.CookieContainer = cookie;         request.Method = "GET";         request.ContentType = "text/plain;charset=utf-8";          if (headers != null)         {             foreach (string key in headers.Keys)             {                 request.Headers.Add(key, headers[key]);             }         }          //发送请求并获取相应回应数据         HttpWebResponse response = request.GetResponse() as HttpWebResponse;         //直到request.GetResponse()程序才开始向目标网页发送Post请求         Stream instream = response.GetResponseStream();         StreamReader sr = new StreamReader(instream, Encoding.UTF8);         //返回结果网页(html)代码         string content = sr.ReadToEnd();         return content;     }     catch (Exception ex)     {         LogUtil.Error(ex);         return string.Empty;     } }

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HttpUtil.HttpGetAsync方法:

你可能写了个假异步,并不能提高请求线程池的吞吐量你可能写了个假异步,并不能提高请求线程池的吞吐量

/// <summary> /// HttpGetAsync /// </summary> /// <param name="url">url路径名称</param> /// <param name="cookie">cookie</param> public static async Task<string> HttpGetAsync(string url, CookieContainer cookie = null, WebHeaderCollection headers = null) {     try     {         // 设置参数         HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest;         request.CookieContainer = cookie;         request.Method = "GET";         request.ContentType = "text/plain;charset=utf-8";          if (headers != null)         {             foreach (string key in headers.Keys)             {                 request.Headers.Add(key, headers[key]);             }         }          //发送请求并获取相应回应数据         HttpWebResponse response = await request.GetResponseAsync() as HttpWebResponse;         //直到request.GetResponse()程序才开始向目标网页发送Post请求         Stream instream = response.GetResponseStream();         StreamReader sr = new StreamReader(instream, Encoding.UTF8);         //返回结果网页(html)代码         string content = sr.ReadToEnd();         return content;     }     catch (Exception ex)     {         LogUtil.Error(ex);         return string.Empty;     } }

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测试代码:

你可能写了个假异步,并不能提高请求线程池的吞吐量你可能写了个假异步,并不能提高请求线程池的吞吐量

/// <summary> /// 测试1 /// </summary> private async void button1_Click(object sender, EventArgs e) {     //task是自己写的独立线程池,为了防止测试过程对CLR线程池和异步线程池造成干扰     _task.Run(() =>     {         Thread.Sleep(200);          int workerThreads1, completionPortThreads1, workerThreads2, completionPortThreads2;         ThreadPool.GetMaxThreads(out workerThreads1, out completionPortThreads1);         ThreadPool.GetAvailableThreads(out workerThreads2, out completionPortThreads2);         Log("假异步 已使用辅助线程:" + (workerThreads1 - workerThreads2) + ", 已使用异步线程:" + (completionPortThreads1 - completionPortThreads2));     });      string str = await GetDataAsync(); }  /// <summary> /// 测试2  /// </summary> private async void button2_Click(object sender, EventArgs e) {     //task是自己写的独立线程池,为了防止测试过程对CLR线程池和异步线程池造成干扰     _task.Run(() =>     {         Thread.Sleep(200);          int workerThreads1, completionPortThreads1, workerThreads2, completionPortThreads2;         ThreadPool.GetMaxThreads(out workerThreads1, out completionPortThreads1);         ThreadPool.GetAvailableThreads(out workerThreads2, out completionPortThreads2);         Log("真异步 已使用辅助线程:" + (workerThreads1 - workerThreads2) + ", 已使用异步线程:" + (completionPortThreads1 - completionPortThreads2));     });      string str = await GetDataAsync2(); }  /// <summary> /// 假异步 /// </summary> private async Task<string> GetDataAsync() {     return await Task.Run<string>(() =>     {         //接口耗时大约1秒         return HttpUtil.HttpGet("http://localhost:8500/api/test/TestGet?val=1", null, null);     }); }  /// <summary> /// 真异步 /// </summary> /// <returns></returns> private async Task<string> GetDataAsync2() {     //接口耗时大约1秒     return await HttpUtil.HttpGetAsync("http://localhost:8500/api/test/TestGet?val=1", null, null); }

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测试截图:

你可能写了个假异步,并不能提高请求线程池的吞吐量

我想知道 WebRequest 类的 GetResponseAsync 方法是怎么实现的,反正使用.NET提供的类,我是无法实现这样的方法。

这篇随笔如果有错误,请指正,我只是抛砖引玉,提出疑问或者说假设。

async await 要一路写到底啊,重构压力真大。