關於.Net Core下因客戶端主動取消導致Request請求[FromBody]模型綁定讀取異常BadHttpRequestException

　　最近我们的接口老是会出现BadHttpRequestException异常，但是手动查看报错的页面却一点问题没有，很奇怪，后来仔细研究这个异常。异常原因其实根据异常对象本身就已经能分析出来了（由于第一次遇到不清楚怎么造成的，尴尬），就是由于无法正常读取Http-Request请求对象里的内容导致的异常！但是什么情况下会导致这个情况，不得而知。  后来百度其他朋友的文章，终于了解到发生当前错误的原因：

　　是由于当请求出现并发，而请求的线程池又不够使用，前面的请求阻塞后面的请求时，后面的请求强制取消后就会导致后面的请求在被接收程序处理Request内容时发生异常，即：BadHttpRequestException

先看下接口是怎么接收的：

[HttpPost]
public async Task<IActionResult> PPIFrameInit([FromBody] PaypalClientRequest parames)
{
      //...  
}

很显然，接口采用的是自动绑定Model模型Request-Body的方式，那么如果按照上述请求就很容易发生下面的异常了。

异常内容如下：

ClientIP：157.185.158.160 
URL：http://www.coowigsby.com/ajax/paydd/PPIFrameInit 
Type：Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException 
Msg：Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException: Unexpected end of request content.
   at Microsoft.AspNetCore.Server.Kestrel.Core.KestrelBadHttpRequestException.Throw(RequestRejectionReason reason)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1ContentLengthMessageBody.ReadAsyncInternal(CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.HttpRequestStream.ReadAsyncInternal(Memory`1 destination, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.WebUtilities.FileBufferingReadStream.ReadAsync(Memory`1 buffer, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.WebUtilities.StreamHelperExtensions.DrainAsync(Stream stream, ArrayPool`1 bytePool, Nullable`1 limit, CancellationToken cancellationToken)
   at Microsoft.AspNetCore.Mvc.Formatters.NewtonsoftJsonInputFormatter.ReadRequestBodyAsync(InputFormatterContext context, Encoding encoding)
   at Microsoft.AspNetCore.Mvc.ModelBinding.Binders.BodyModelBinder.BindModelAsync(ModelBindingContext bindingContext)
   at Microsoft.AspNetCore.Mvc.ModelBinding.ParameterBinder.BindModelAsync(ActionContext actionContext, IModelBinder modelBinder, IValueProvider valueProvider, ParameterDescriptor parameter, ModelMetadata metadata, Object value, Object container)
   at Microsoft.AspNetCore.Mvc.Controllers.ControllerBinderDelegateProvider.<>c__DisplayClass0_0.<<CreateBinderDelegate>g__Bind|0>d.MoveNext()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeInnerFilterAsync>g__Awaited|13_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|24_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
--- End of stack trace from previous location ---
   at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Awaited|17_0(ResourceInvoker invoker, Task task, IDisposable scope)
   at Microsoft.AspNetCore.Routing.EndpointMiddleware.<Invoke>g__AwaitRequestTask|6_0(Endpoint endpoint, Task requestTask, ILogger logger)
   at MeShop.CacheResponse.CacheResponseMiddleware.Invoke(HttpContext httpContext) in /builds/sitegroup/meshop/meshop/MeShop.CacheResponse/CacheResponseMiddleware.cs:line 56
   at MeShop.View.Shop.Models.CheckExpirationMiddleware.Invoke(HttpContext httpContext) in /builds/sitegroup/meshop/meshop/MeShop.View.Shop/Models/CheckExpirationMiddleware.cs:line 38
   at MeShop.WebCommon.Cache.ResponseDistributedCacheMiddleware.Invoke(HttpContext httpContext) in /builds/sitegroup/meshop/meshop/MeShop.WebCommon/Cache/ResponseDistributedCacheMiddleware.cs:line 105
   at Microsoft.AspNetCore.ResponseCaching.ResponseCachingMiddleware.Invoke(HttpContext httpContext)
   at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at MeShop.WebCommon.CircuitBreakerWebMiddleware.<>c__DisplayClass13_0.<<InvokeAsync>b__1>d.MoveNext() in /builds/sitegroup/meshop/meshop/MeShop.WebCommon/Middleware/CircuitBreakerWebMiddleware.cs:line 246
--- End of stack trace from previous location ---
   at Polly.AsyncPolicy.<>c__DisplayClass40_0.<<ImplementationAsync>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at Polly.CircuitBreaker.AsyncCircuitBreakerPolicy.<>c__DisplayClass8_0`1.<<ImplementationAsync>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at Polly.CircuitBreaker.AsyncCircuitBreakerEngine.ImplementationAsync[TResult](Func`3 action, Context context, CancellationToken cancellationToken, Boolean continueOnCapturedContext, ExceptionPredicates shouldHandleExceptionPredicates, ResultPredicates`1 shouldHandleResultPredicates, ICircuitController`1 breakerController)
   at Polly.CircuitBreaker.AsyncCircuitBreakerPolicy.ImplementationAsync[TResult](Func`3 action, Context context, CancellationToken cancellationToken, Boolean continueOnCapturedContext)
   at Polly.AsyncPolicy.ExecuteAsync(Func`3 action, Context context, CancellationToken cancellationToken, Boolean continueOnCapturedContext)
   at MeShop.WebCommon.CircuitBreakerWebMiddleware.InvokeAsync(HttpContext context) in /builds/sitegroup/meshop/meshop/MeShop.WebCommon/Middleware/CircuitBreakerWebMiddleware.cs:line 275

这里列举一下本地调试的复现步骤（本地调试是单线程）：

• 在请求处理过程的某处设置断点
• 在PostMan或浏览器上先发送A请求，命中断点，不继续往下处理，让请求阻塞
• 继续发放B请求，这时请求阻塞中，然后点击取消请求
• 释放断点继续处理，结果是A请求正常处理结束，B请求处理时抛出异常

解决方法有三种（参考的博客里只介绍了一种）：

• 1_可选择在全局异常过滤器中不处理该异常，不打印错误日志(有掩耳盗铃的嫌疑，不推荐)；
• 2_可以将接口[FromBody]由自动绑定改成代码读取接收，使用try-catch捕获异常单独处理（跟1类似，也不推荐）；
• 3_可以增加最小线程池数量，使其能够拥有足够的线程处理并发请求（确实访问量太大，可以使用）；
• 4_优化现有的代码：分析当时的请求为何造成了线程不够用的原因，把耗时较长造成阻塞的有问题的方法处理掉，更新后再继续观察（适用于访问量没有那么大，部分接口代码质量不好的情况时使用）；

参考博客：关于.Net Core3.0下因客户端主动取消请求导致的Request.Body异常