你可能写了个假异步,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:
/// <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();
        instream.Close();
        return content;
    }
    catch (Exception ex)
    {
        LogUtil.Error(ex);
        return string.Empty;
    }
}
View Code

HttpUtil.HttpGetAsync方法:

/// <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();
        instream.Close();
        return content;
    }
    catch (Exception ex)
    {
        LogUtil.Error(ex);
        return string.Empty;
    }
}
View Code

测试代码:

/// <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);
}
View Code

测试截图:

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。

如果在异步方法中调用同步方法,又不想占用CLR线程池的线程,可以把耗时操作放到自己写的独立线程池中,例如:

/// <summary>
/// 测试GET请求
/// </summary>
/// <param name="val">测试参数</param>
[HttpGet]
[Route("TestGet")]
[SwaggerResponse(HttpStatusCode.OK, "返回JSON", typeof(JsonListResult<TestGetResult>))]
public async Task<HttpResponseMessage> TestGetAsync(string val)
{
    var task = TaskHelper.RequestTask.Run(() => //使用自己写的独立线程池
    {
        List<TestGetResult> list = new List<TestGetResult>();

        Thread.Sleep(5000); //模拟耗时

        for (int i = 1; i <= 10; i++)
        {
            TestGetResult item = new TestGetResult();
            item.testValue1 = i.ToString();
            item.testValue2 = i;
            item.testValue3 = "这是传入参数:" + val;
            list.Add(item);
        }

        var jsonResult = new JsonListResult<TestGetResult>(list, list.Count);

        return ApiHelper.ToJson(jsonResult);
    });

    return await task;
}
View Code

 

 

 

 

posted @ 2020-08-01 16:50  秋荷雨翔  阅读(197)  评论(6编辑  收藏