我有困难，了解背后的ExecutionContext的机制。
从我在线阅读，上下文相关的项目，如安全（螺纹校长），文化等，应在整个异步线程工作的执行单元的范围内流动。
我虽然遇到非常混乱，有潜在危险的错误。 我注意到我的线程的CurrentPrincipal是越来越跨越异步执行丢失。
下面是一个例子的ASP.NET Web API的情景：
首先，让我们设置有用于测试目的的两个委托处理一个简单的Web API配置。
他们做的是写出调试信息并通过对通过请求/响应，除了第一次“DummyHandler”，这将线程的主要以及一块被跨越的上下文共享数据（请求的关联ID）。
public static class WebApiConfig
{
public static void Register(HttpConfiguration config)
{
config.MessageHandlers.Add(new DummyHandler());
config.MessageHandlers.Add(new AnotherDummyHandler());
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
}
}
public class DummyHandler : DelegatingHandler
{
protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
{
CallContext.LogicalSetData("rcid", request.GetCorrelationId());
Thread.CurrentPrincipal = new ClaimsPrincipal(new ClaimsPrincipal(new ClaimsIdentity(new[]{ new Claim("http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name", "dgdev") }, "myauthisthebest")));
Debug.WriteLine("Dummy Handler Thread: {0}", Thread.CurrentThread.ManagedThreadId);
Debug.WriteLine("User: {0}", (Object)Thread.CurrentPrincipal.Identity.Name);
Debug.WriteLine("RCID: {0}", CallContext.LogicalGetData("rcid"));
return base.SendAsync(request, cancellationToken)
.ContinueWith(task =>
{
Debug.WriteLine("Dummy Handler Thread: {0}", Thread.CurrentThread.ManagedThreadId);
Debug.WriteLine("User: {0}", (Object)Thread.CurrentPrincipal.Identity.Name);
Debug.WriteLine("RCID: {0}", CallContext.LogicalGetData("rcid"));
return task.Result;
});
}
}
public class AnotherDummyHandler : MessageProcessingHandler
{
protected override HttpRequestMessage ProcessRequest(HttpRequestMessage request, CancellationToken cancellationToken)
{
Debug.WriteLine(" Another Dummy Handler Thread: {0}", Thread.CurrentThread.ManagedThreadId);
Debug.WriteLine(" User: {0}", (Object)Thread.CurrentPrincipal.Identity.Name);
Debug.WriteLine(" RCID: {0}", CallContext.LogicalGetData("rcid"));
return request;
}
protected override HttpResponseMessage ProcessResponse(HttpResponseMessage response, CancellationToken cancellationToken)
{
Debug.WriteLine(" Another Dummy Handler Thread: {0}", Thread.CurrentThread.ManagedThreadId);
Debug.WriteLine(" User: {0}", (Object)Thread.CurrentPrincipal.Identity.Name);
Debug.WriteLine(" RCID: {0}", CallContext.LogicalGetData("rcid"));
return response;
}
}
够简单。 接下来，让我们添加一个ApiController来处理HTTP POST，因为如果你上传的文件。
public class UploadController : ApiController
{
public async Task<HttpResponseMessage> PostFile()
{
Debug.WriteLine(" Thread: {0}", Thread.CurrentThread.ManagedThreadId);
Debug.WriteLine(" User: {0}", (Object)Thread.CurrentPrincipal.Identity.Name);
Debug.WriteLine(" RCID: {0}", CallContext.LogicalGetData("rcid"));
if (!Request.Content.IsMimeMultipartContent())
{
throw new HttpResponseException(HttpStatusCode.UnsupportedMediaType);
}
try
{
await Request.Content.ReadAsMultipartAsync(
new MultipartFormDataStreamProvider(
HttpRuntime.AppDomainAppPath + @"upload\temp"));
Debug.WriteLine(" Thread: {0}", Thread.CurrentThread.ManagedThreadId);
Debug.WriteLine(" User: {0}", (Object)Thread.CurrentPrincipal.Identity.Name);
Debug.WriteLine(" RCID: {0}", CallContext.LogicalGetData("rcid"));
return new HttpResponseMessage(HttpStatusCode.Created);
}
catch (Exception e)
{
return Request.CreateErrorResponse(HttpStatusCode.InternalServerError, e);
}
}
}
在运行使用Fiddler测试，这是我收到的输出：
Dummy Handler Thread: 63
User: dgdev
RCID: 6d542847-4ceb-4511-85e5-d1b5bf3be476
Another Dummy Handler Thread: 63
User: dgdev
RCID: 6d542847-4ceb-4511-85e5-d1b5bf3be476
Thread: 63
User: dgdev
RCID: 6d542847-4ceb-4511-85e5-d1b5bf3be476
Thread: 77
User: <<< PRINCIPAL IS LOST AFTER ASYNC
RCID: 6d542847-4ceb-4511-85e5-d1b5bf3be476
Another Dummy Handler Thread: 63
User: <<< PRINCIPAL IS STILL LOST
RCID: 6d542847-4ceb-4511-85e5-d1b5bf3be476
Dummy Handler Thread: 65
User: dgdev <<< PRINCIPAL IS BACK?!?
RCID: 6d542847-4ceb-4511-85e5-d1b5bf3be476
为了使问题更混乱，当我追加后续的异步线路：
await Request.Content.ReadAsMultipartAsync(
new MultipartFormDataStreamProvider(..same as before..))
.ConfigureAwait(false); <<<<<<
我现在收到此输出：
Dummy Handler Thread: 40
User: dgdev
RCID: 8d944500-cb52-4362-8537-dab405fa12a2
Another Dummy Handler Thread: 40
User: dgdev
RCID: 8d944500-cb52-4362-8537-dab405fa12a2
Thread: 40
User: dgdev
RCID: 8d944500-cb52-4362-8537-dab405fa12a2
Thread: 65
User: dgdev <<< PRINCIPAL IS HERE!
RCID: 8d944500-cb52-4362-8537-dab405fa12a2
Another Dummy Handler Thread: 65
User: <<< PRINCIPAL IS LOST
RCID: 8d944500-cb52-4362-8537-dab405fa12a2
Dummy Handler Thread: 40
User: dgdev
RCID: 8d944500-cb52-4362-8537-dab405fa12a2
这里的关键是这样的。 异步下面的代码我其实叫我的业务逻辑或只要求安全上下文正确设置。 目前正在进行一个潜在的完整性问题。
任何人都可以帮助一些启发一个发生了什么？
提前致谢。
