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c# - HttpClient 从不在 IIS 上发送请求

转载 作者:行者123 更新时间:2023-12-05 08:57:26 32 4
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我遇到了一个奇怪的问题并尝试了各种方法来让它工作。

我的 Web API 项目中有一个反向代理委托(delegate)处理程序,用于拦截对内部资源、文件等的请求,从我们的外部站点到我们 DMZ 内的内部站点...

using System;
using System.Configuration;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Formatting;
using System.Threading;
using System.Threading.Tasks;
using System.Web.Http;

namespace Resources.API
{
public class ProxyHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var routes = new[]{
"/api/videos",
"/api/documents"
};

// check whether we need to proxy this request
var passThrough = !routes.Any(route => request.RequestUri.LocalPath.StartsWith(route));
if (passThrough)
return await base.SendAsync(request, cancellationToken);

// got a hit forward the request to the proxy Web API
return await ForwardRequest(request, cancellationToken);
}

private static async Task<HttpResponseMessage> ForwardRequest(HttpRequestMessage request, CancellationToken cancellationToken)
{
//Clone the request and forward to the internal proxy site
var proxyUrl = ConfigurationManager.AppSettings["ProxyUrl"];
var baseUri = new UriBuilder(proxyUrl);

//clone the requestUri and point it at the proxy site
var forwardedUri = new UriBuilder(request.RequestUri)
{
Scheme = baseUri.Scheme,
Host = baseUri.Host,
Port = baseUri.Port
};

var forwardRequest = new HttpRequestMessage(request.Method, forwardedUri.Uri);

if (request.Method == HttpMethod.Post || request.Method == HttpMethod.Put)
{
var stream = new MemoryStream();
await request.Content.CopyToAsync(stream);
stream.Seek(0, SeekOrigin.Begin);
forwardRequest.Content = new StreamContent(stream);

//copy the content headers
foreach (var header in request.Content.Headers)
{
forwardRequest.Content.Headers.TryAddWithoutValidation(header.Key, header.Value);
}
};

forwardRequest.Version = request.Version;

foreach (var prop in request.Properties)
{
forwardRequest.Properties.Add(prop);
}

foreach (var header in request.Headers)
{
forwardRequest.Headers.TryAddWithoutValidation(header.Key, header.Value);
}

var client = new HttpClient(new HttpClientHandler(), disposeHandler: false);
var task = await Task.Factory
.StartNew(async () => await client.SendAsync(forwardRequest, HttpCompletionOption.ResponseHeadersRead,
cancellationToken),
CancellationToken.None,
TaskCreationOptions.LongRunning,
TaskScheduler.Default);
try
{
task.Wait(cancellationToken);
}
catch (Exception e)
{
return new HttpResponseMessage(HttpStatusCode.InternalServerError)
{
Content =
new ObjectContent<HttpError>(new HttpError(e, includeErrorDetail: true),
new JsonMediaTypeFormatter())
};
}

return task.Result;
}
}
}

编辑:还尝试等待和返回任务...

            try
{
return await task;
}

这在 IIS Express 8.0 上运行良好,但在 Windows 7 Professional(我的开发机器)上的 IIS 7.5 或 Windows Server 2012 上的 IIS 8.0 上运行不正常。

创建的HttpClient从未真正通过网络发送请求(由 Fiddler 检查)并最终超时并抛出 AggregateException带着 child TaskCanceledException .

task.Wait 上设置断点,我注意到,由于某种原因,断点被击中 10 次,而不是通过 IIS Express 运行时一次。

我已经尝试了各种方法来尝试让它工作,包括大量搜索 Google 和 SO,但似乎没有任何效果。

有人知道为什么会这样吗?或者可以解释我做错了什么?

最佳答案

想通了。必须更改请求中的 Host header 才能正确发送。它实际上忽略了 RequestUri 并使用 Host header 来决定将请求实际发送到哪里。

forwardRequest.Headers.Host = forwardRequest.RequestUri.Host;

现在工作正常,IIS 现在将适本地发送请求。仍然让我想知道为什么 IIS Express 似乎不需要更改 Host header !

完整代码...添加了 X-Forwarded-ForX-Forwarded-Host 以及良好的衡量标准。

using System;
using System.Configuration;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Http;
using System.Net.Http.Formatting;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using System.Web;
using System.Web.Http;

namespace Resources.API
{
public class ProxyHandler : DelegatingHandler
{
protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
var routes = new[]{
"/api/videos",
"/api/documents"
};

// check whether we need to proxy this request
var passThrough = !routes.Any(route => request.RequestUri.LocalPath.StartsWith(route));
if (passThrough)
return await base.SendAsync(request, cancellationToken);

// got a hit forward the request to the proxy Web API
//return GetResponseFromProxy(request);

//Nicer method using HttpClient - but it doesn't work on IIS!
return await ForwardRequest(request, cancellationToken);
}

private static async Task<HttpResponseMessage> ForwardRequest(HttpRequestMessage request, CancellationToken cancellationToken)
{
//Clone the request and forward to the internal proxy site
var proxyUrl = ConfigurationManager.AppSettings["ProxyUrl"];
var baseUri = new UriBuilder(proxyUrl);

//clone the requestUri and point it at the proxy site
var forwardedUri = new UriBuilder(request.RequestUri)
{
Scheme = baseUri.Scheme,
Host = baseUri.Host,
Port = baseUri.Port
};

var forwardRequest = new HttpRequestMessage(request.Method, forwardedUri.Uri);

if (request.Method == HttpMethod.Post || request.Method == HttpMethod.Put)
{
var stream = new MemoryStream();
await request.Content.CopyToAsync(stream);
stream.Seek(0, SeekOrigin.Begin);
forwardRequest.Content = new StreamContent(stream);

//copy the content headers
foreach (var header in request.Content.Headers)
{
forwardRequest.Content.Headers.TryAddWithoutValidation(header.Key, header.Value);
}
};

forwardRequest.Version = request.Version;

foreach (var prop in request.Properties)
{
forwardRequest.Properties.Add(prop);
}

foreach (var header in request.Headers)
{
forwardRequest.Headers.TryAddWithoutValidation(header.Key, header.Value);
}

// Don't forget to change the Host header to refer to the proxy
forwardRequest.Headers.Host = forwardRequest.RequestUri.Host;

//Add the relevant X-Forwarded headers
var xForwardedHost = request.Headers.Host;
forwardRequest.Headers.Add("X-Forwarded-Host", xForwardedHost);

var xForwardedFor = HttpContext.Current.Request.UserHostAddress;
forwardRequest.Headers.Add("X-Forwarded-For", xForwardedFor);

var client = new HttpClient(new HttpClientHandler(), disposeHandler: false);

try
{
return await client.SendAsync(forwardRequest, HttpCompletionOption.ResponseHeadersRead,
cancellationToken);
}
catch (Exception e)
{
return new HttpResponseMessage(HttpStatusCode.InternalServerError)
{
Content =
new ObjectContent<HttpError>(new HttpError(e, includeErrorDetail: true),
new JsonMediaTypeFormatter())
};
}
}
}
}

关于c# - HttpClient 从不在 IIS 上发送请求,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/33014188/

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