Web Api 中的 HttpClient 非常慢

Question

我正在使用 ASP.NET WebApi (ApiController) 为我的应用程序实现一个代理，并使用 HttpClient 在我的授权下发出请求 header。它工作正常，但速度非常慢。下面是主要代码，然后是全局初始化（使用 DefaultConnectionLimit）和 web.config 相关部分。

如您所见，我已经在使用没有代理的 static/shared HttpClient object 和 HttpCompletionOption.ResponseHeadersRead 实际请求.这个 WebApi 端点被并行调用，工作正常。

整个代码运行速度足够快，但是当我使用 ResponseHeadersRead async 时，HttpRequestMessage 被返回并且 body 的其余部分被下载并直接流式传输到 client/caller。

这里 a video 显示了问题。

public class ProxyController : ApiController
{
  private const string BASE_URL = "https://developer.api.autodesk.com";
  private const string PROXY_ROUTE = "api/viewerproxy/";


  // HttpClient has been designed to be re-used for multiple calls. Even across multiple threads. 
  // 
  private static HttpClient _httpClient;

  [HttpGet]
  [Route(PROXY_ROUTE + "{*.}")]
  public async Task<HttpResponseMessage> Get()
  {
    if (_httpClient == null)
    {
      _httpClient = new HttpClient(new HttpClientHandler() 
         {
            UseProxy = false,
            Proxy = null
         });
      _httpClient.BaseAddress = new Uri(BASE_URL);
    }

    string url = Request.RequestUri.AbsolutePath.Replace(PROXY_ROUTE, string.Empty);
    string absoluteUrl = url + Request.RequestUri.Query;

    try
    {
      HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, absoluteUrl);
      request.Headers.Add("Authorization", "Bearer " + AccessToken);

      HttpResponseMessage response = await _httpClient.SendAsync(request, HttpCompletionOption.ResponseHeadersRead);

      return response;
    }
    catch (Exception e)
    {
      return new HttpResponseMessage(System.Net.HttpStatusCode.InternalServerError);
    }
  }
}

Global.asax，虽然我不认为是连接限制的问题，因为所有请求都已处理，但太慢了...

public class Global : System.Web.HttpApplication
{
  protected void Application_Start(object sender, EventArgs e)
  {
    GlobalConfiguration.Configure(Config.WebApiConfig.Register);

    ServicePointManager.UseNagleAlgorithm = true;
    ServicePointManager.Expect100Continue = false;
    ServicePointManager.CheckCertificateRevocationList = true;
    ServicePointManager.DefaultConnectionLimit = int.MaxValue;
  }
}

和部分Web.Config

 <system.web>
    <compilation debug="true" targetFramework="4.6" />
    <httpRuntime targetFramework="4.6" maxRequestLength="2097151" requestLengthDiskThreshold="16384" requestPathInvalidCharacters="&lt;,&gt;,*,%,&amp;,\,?" />
  </system.web>

Answer 1

通过删除 web.config 的 <system.diagnostics> 部分解决。它似乎导致了过多的输出并减慢了所有 HttpClient 请求。

郑重声明，这是我使用并导致所有 HttpClient.SendAsync 调用缓慢的代码。但这对于跟踪连接问题很有用:-)

<system.diagnostics>
  <sources>
    <source name="System.Net" tracemode="protocolonly" maxdatasize="1024">
      <listeners>
        <add name="System.Net"/>
      </listeners>
    </source>
    <source name="System.Net.Cache">
      <listeners>
        <add name="System.Net"/>
      </listeners>
    </source>
    <source name="System.Net.Http">
      <listeners>
        <add name="System.Net"/>
      </listeners>
    </source>
  </sources>
  <switches>
    <add name="System.Net" value="Verbose"/>
    <add name="System.Net.Cache" value="Verbose"/>
    <add name="System.Net.Http" value="Verbose"/>
    <add name="System.Net.Sockets" value="Verbose"/>
    <add name="System.Net.WebSockets" value="Verbose"/>
  </switches>
  <sharedListeners>
    <add name="System.Net"
      type="System.Diagnostics.TextWriterTraceListener"
      initializeData="network.log"
    />
  </sharedListeners>
  <trace autoflush="true"/>
</system.diagnostics>

Web Api 中的 HttpClient 非常慢

HttpClient on WebApi is extremely slow

c#

asp.net

asp.net-web-api

dotnet-httpclient

asp.net-web-api-routing