[WIP] use HttpContext.RequestAborted to support cancel a request (#902)

* use HttpContext.RequestAborted to support cancel a request

* register context.HttpContext.RequestAborted.ThrowIfCancellationRequested() in ExceptionHandlerMiddleware

* add LangVersion

* add default number to OcelotErrorCode
fix unit test

* revert back to one line

Directory.Build.props

@@ -1,5 +1,7 @@
 <Project>
   <PropertyGroup>
+    <LangVersion>latest</LangVersion>
+
     <RepositoryType>git</RepositoryType>
     <RepositoryUrl>https://github.com/ThreeMammals/Ocelot</RepositoryUrl>
     <!-- Optional: Publish the repository URL in the built .nupkg (in the NuSpec <Repository> element) -->

src/Ocelot/Errors/Middleware/ExceptionHandlerMiddleware.cs

@@ -1,14 +1,14 @@
 namespace Ocelot.Errors.Middleware
 {
     using Configuration;
-    using System;
-    using System.Linq;
-    using System.Threading.Tasks;
     using Ocelot.Configuration.Repository;
     using Ocelot.Infrastructure.Extensions;
     using Ocelot.Infrastructure.RequestData;
     using Ocelot.Logging;
     using Ocelot.Middleware;
+    using System;
+    using System.Linq;
+    using System.Threading.Tasks;
 
     /// <summary>
     /// Catches all unhandled exceptions thrown by middleware, logs and returns a 500
@@ -34,6 +34,8 @@ namespace Ocelot.Errors.Middleware
         {
             try
             {
+                context.HttpContext.RequestAborted.ThrowIfCancellationRequested();
+
                 //try and get the global request id and set it for logs...
                 //should this basically be immutable per request...i guess it should!
                 //first thing is get config
@@ -52,6 +54,14 @@ namespace Ocelot.Errors.Middleware
 
                 await _next.Invoke(context);
             }
+            catch (OperationCanceledException e) when (context.HttpContext.RequestAborted.IsCancellationRequested)
+            {
+                Logger.LogDebug("operation canceled");
+                if (!context.HttpContext.Response.HasStarted)
+                {
+                    context.HttpContext.Response.StatusCode = 499;
+                }
+            }
             catch (Exception e)
             {
                 Logger.LogDebug("error calling middleware");

src/Ocelot/Errors/OcelotErrorCode.cs

@@ -2,42 +2,43 @@
 {
     public enum OcelotErrorCode
     {
-        UnauthenticatedError, 
+        UnauthenticatedError = 0,
-        UnknownError,
+        UnknownError = 1,
-        DownstreampathTemplateAlreadyUsedError,
+        DownstreampathTemplateAlreadyUsedError = 2,
-        UnableToFindDownstreamRouteError,
+        UnableToFindDownstreamRouteError = 3,
-        CannotAddDataError,
+        CannotAddDataError = 4,
-        CannotFindDataError,
+        CannotFindDataError = 5,
-        UnableToCompleteRequestError,
+        UnableToCompleteRequestError = 6,
-        UnableToCreateAuthenticationHandlerError,
+        UnableToCreateAuthenticationHandlerError = 7,
-        UnsupportedAuthenticationProviderError,
+        UnsupportedAuthenticationProviderError = 8,
-        CannotFindClaimError,
+        CannotFindClaimError = 9,
-        ParsingConfigurationHeaderError,
+        ParsingConfigurationHeaderError = 10,
-        NoInstructionsError,
+        NoInstructionsError = 11,
-        InstructionNotForClaimsError,
+        InstructionNotForClaimsError = 12,
-        UnauthorizedError,
+        UnauthorizedError = 13,
-        ClaimValueNotAuthorisedError,
+        ClaimValueNotAuthorisedError = 14,
-        ScopeNotAuthorisedError,
+        ScopeNotAuthorisedError = 15,
-        UserDoesNotHaveClaimError,
+        UserDoesNotHaveClaimError = 16,
-        DownstreamPathTemplateContainsSchemeError,
+        DownstreamPathTemplateContainsSchemeError = 17,
-        DownstreamPathNullOrEmptyError,
+        DownstreamPathNullOrEmptyError = 18,
-        DownstreamSchemeNullOrEmptyError,
+        DownstreamSchemeNullOrEmptyError = 19,
-        DownstreamHostNullOrEmptyError,
+        DownstreamHostNullOrEmptyError = 20,
-        ServicesAreNullError,
+        ServicesAreNullError = 21,
-        ServicesAreEmptyError,
+        ServicesAreEmptyError = 22,
-        UnableToFindServiceDiscoveryProviderError,
+        UnableToFindServiceDiscoveryProviderError = 23,
-        UnableToFindLoadBalancerError,
+        UnableToFindLoadBalancerError = 24,
-        RequestTimedOutError,
+        RequestTimedOutError = 25,
-        UnableToFindQoSProviderError,
+        UnableToFindQoSProviderError = 26,
-        UnmappableRequestError,
+        UnmappableRequestError = 27,
-        RateLimitOptionsError,
+        RateLimitOptionsError = 28,
-        PathTemplateDoesntStartWithForwardSlash,
+        PathTemplateDoesntStartWithForwardSlash = 29,
-        FileValidationFailedError,
+        FileValidationFailedError = 30,
-        UnableToFindDelegatingHandlerProviderError,
+        UnableToFindDelegatingHandlerProviderError = 31,
-        CouldNotFindPlaceholderError,
+        CouldNotFindPlaceholderError = 32,
-        CouldNotFindAggregatorError,
+        CouldNotFindAggregatorError = 33,
-        CannotAddPlaceholderError,
+        CannotAddPlaceholderError = 34,
-        CannotRemovePlaceholderError,
+        CannotRemovePlaceholderError = 35,
-        QuotaExceededError
+        QuotaExceededError = 36,
+        RequestCanceled = 37,
     }
 }

src/Ocelot/Requester/HttpClientHttpRequester.cs

@@ -1,9 +1,9 @@
-using System;
-using System.Net.Http;
-using System.Threading.Tasks;
 using Ocelot.Logging;
 using Ocelot.Middleware;
 using Ocelot.Responses;
+using System;
+using System.Net.Http;
+using System.Threading.Tasks;
 
 namespace Ocelot.Requester
 {
@@ -33,7 +33,7 @@ namespace Ocelot.Requester
 
             try
             {
-                var response = await httpClient.SendAsync(context.DownstreamRequest.ToHttpRequestMessage());
+                var response = await httpClient.SendAsync(context.DownstreamRequest.ToHttpRequestMessage(), context.HttpContext.RequestAborted);
                 return new OkResponse<HttpResponseMessage>(response);
             }
             catch (Exception exception)

src/Ocelot/Requester/HttpClientWrapper.cs

@@ -1,4 +1,5 @@
 using System.Net.Http;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Ocelot.Requester
@@ -15,9 +16,9 @@ namespace Ocelot.Requester
             Client = client;
         }
 
-        public Task<HttpResponseMessage> SendAsync(HttpRequestMessage request)
+        public Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken = default)
         {
-            return Client.SendAsync(request);
+            return Client.SendAsync(request, cancellationToken);
         }
     }
 }

src/Ocelot/Requester/HttpExeptionToErrorMapper.cs

@@ -1,9 +1,9 @@
 namespace Ocelot.Requester
 {
-    using System;
-    using System.Collections.Generic;
     using Errors;
     using Microsoft.Extensions.DependencyInjection;
+    using System;
+    using System.Collections.Generic;
 
     public class HttpExeptionToErrorMapper : IExceptionToErrorMapper
     {
@@ -23,6 +23,11 @@ namespace Ocelot.Requester
                 return _mappers[type](exception);
             }
 
+            if (type == typeof(OperationCanceledException))
+            {
+                return new RequestCanceledError(exception.Message);
+            }
+
             return new UnableToCompleteRequestError(exception);
         }
     }

src/Ocelot/Requester/IHttpClient.cs

@@ -1,5 +1,5 @@
-using System;
+using System.Net.Http;
-using System.Net.Http;
+using System.Threading;
 using System.Threading.Tasks;
 
 namespace Ocelot.Requester
@@ -8,6 +8,6 @@ namespace Ocelot.Requester
     {
         HttpClient Client { get; }
 
-        Task<HttpResponseMessage> SendAsync(HttpRequestMessage request);
+        Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken = default);
     }
 }

src/Ocelot/Requester/RequestCanceledError.cs

@@ -0,0 +1,11 @@
+using Ocelot.Errors;
+
+namespace Ocelot.Requester
+{
+    public class RequestCanceledError : Error
+    {
+        public RequestCanceledError(string message) : base(message, OcelotErrorCode.RequestCanceled)
+        {
+        }
+    }
+}

src/Ocelot/Responder/ErrorsToHttpStatusCodeMapper.cs

@@ -1,6 +1,6 @@
+using Ocelot.Errors;
 using System.Collections.Generic;
 using System.Linq;
-using Ocelot.Errors;
 
 namespace Ocelot.Responder
 {
@@ -27,6 +27,14 @@ namespace Ocelot.Responder
                 return 503;
             }
 
+            if (errors.Any(e => e.Code == OcelotErrorCode.RequestCanceled))
+            {
+                // status code refer to
+                // https://stackoverflow.com/questions/46234679/what-is-the-correct-http-status-code-for-a-cancelled-request?answertab=votes#tab-top
+                // https://httpstatuses.com/499
+                return 499;
+            }
+
             if (errors.Any(e => e.Code == OcelotErrorCode.UnableToFindDownstreamRouteError))
             {
                 return 404;

test/Ocelot.UnitTests/Requester/HttpExeptionToErrorMapperTests.cs

@@ -30,6 +30,14 @@
             error.ShouldBeOfType<UnableToCompleteRequestError>();
         }
 
+        [Fact]
+        public void should_return_request_canceled()
+        {
+            var error = _mapper.Map(new OperationCanceledException());
+
+            error.ShouldBeOfType<RequestCanceledError>();
+        }
+
         [Fact]
         public void should_return_error_from_mapper()
         {

test/Ocelot.UnitTests/Responder/ErrorsToHttpStatusCodeMapperTests.cs

@@ -1,9 +1,9 @@
-using System;
+using Ocelot.Errors;
-using System.Collections.Generic;
-using System.Net;
-using Ocelot.Errors;
 using Ocelot.Responder;
 using Shouldly;
+using System;
+using System.Collections.Generic;
+using System.Net;
 using TestStack.BDDfy;
 using Xunit;
 
@@ -125,7 +125,7 @@ namespace Ocelot.UnitTests.Responder
             // If this test fails then it's because the number of error codes has changed.
             // You should make the appropriate changes to the test cases here to ensure
             // they cover all the error codes, and then modify this assertion.
-            Enum.GetNames(typeof(OcelotErrorCode)).Length.ShouldBe(37, "Looks like the number of error codes has changed. Do you need to modify ErrorsToHttpStatusCodeMapper?");
+            Enum.GetNames(typeof(OcelotErrorCode)).Length.ShouldBe(38, "Looks like the number of error codes has changed. Do you need to modify ErrorsToHttpStatusCodeMapper?");
         }
 
         private void ShouldMapErrorToStatusCode(OcelotErrorCode errorCode, HttpStatusCode expectedHttpStatusCode)
@@ -137,7 +137,7 @@ namespace Ocelot.UnitTests.Responder
         {
             var errors = new List<Error>();
 
-            foreach(var errorCode in errorCodes)
+            foreach (var errorCode in errorCodes)
             {
                 errors.Add(new AnyError(errorCode));
             }