Kestrel在FIN及请求结束后出现BadHttpRequestException问题求助

问题背景 #

基于.NET 6构建的Minimal API部署在Docker容器并托管于AWS，客户端为Wordpress，通过PHP Curl调用API。上线后日志中频繁出现Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException: Unexpected end of request content异常，但请求实际已正常处理并返回200状态码，且该异常无法被自定义异常中间件捕获。

异常日志 #

1 "Connection id \"{ConnectionId}\" accepted.",
2 "Connection id \"{ConnectionId}\" started.",
3 "{HostingRequestStartingLog:l}",
4 "{CandidateCount} candidate(s) found for the request path '{Path}'",
5 "Request matched endpoint '{EndpointName}'",
6 "The request has an origin header: '{origin}'.",
7 "CORS policy execution successful.",
8 "Successfully validated the token.",
9 "AuthenticationScheme: {AuthenticationScheme} was successfully authenticated.",
10"AuthenticationScheme: {AuthenticationScheme} was successfully authenticated.",
11"Authorization was successful.",
12"Executing endpoint '{EndpointName}'",
13"Writing value of type '{Type}' with status code '200'.",
14"Executed endpoint '{EndpointName}'",
15"HTTP {RequestMethod} {RequestPath} responded 200 in {Elapsed:0.0000} ms",
16"Connection id \"{ConnectionId}\" completed keep alive response.",
17"{HostingRequestFinishedLog:l}",
18"Connection id \"{ConnectionId}\" received FIN.",
19"Connection id \"{ConnectionId}\", Request id \"{TraceIdentifier}\": started reading request body.",
20"Connection id \"{ConnectionId}\" sending FIN because: \"{Reason}\"",
21"Connection id \"{ConnectionId}\" disconnecting.",
22"Connection id \"{ConnectionId}\" bad request data: \"{message}\"",
23"Exception": "Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException: Unexpected end of request content.\n   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1ContentLengthMessageBody.TryReadInternal(ReadResult& readResult)\n   at Microsoft.AspNetCore.Server.Kestrel.Core.Internal.Http.Http1MessageBody.OnConsumeAsync()"
24"Connection id \"{ConnectionId}\", Request id \"{TraceIdentifier}\": done reading request body.",
25"Connection id \"{ConnectionId}\" stopped.",

正常日志 #

1 "Connection id \"{ConnectionId}\" accepted.",
2 "Connection id \"{ConnectionId}\" started.",
3 "{HostingRequestStartingLog:l}",
4 "{CandidateCount} candidate(s) found for the request path '{Path}'",
5 "Request matched endpoint '{EndpointName}'",
6 "The request has an origin header: '{origin}'.",
7 "CORS policy execution successful.",
8 "Successfully validated the token.",
9 "AuthenticationScheme: {AuthenticationScheme} was successfully authenticated.",
10"AuthenticationScheme: {AuthenticationScheme} was successfully authenticated.",
11"Authorization was successful.",
12"Executing endpoint '{EndpointName}'",
13"Writing value of type '{Type}' with status code '200'.",
14"Executed endpoint '{EndpointName}'",
15"HTTP {RequestMethod} {RequestPath} responded 200 in {Elapsed:0.0000} ms",
16"Connection id \"{ConnectionId}\" completed keep alive response.",
17"{HostingRequestFinishedLog:l}",
18"Connection id \"{ConnectionId}\", Request id \"{TraceIdentifier}\": started reading request body.",
19"Connection id \"{ConnectionId}\", Request id \"{TraceIdentifier}\": done reading request body.",
20"Connection id \"{ConnectionId}\" received FIN.",
21"Connection id \"{ConnectionId}\" disconnecting.",
22"Connection id \"{ConnectionId}\" sending FIN because: \"{Reason}\"",
23"Connection id \"{ConnectionId}\" stopped.",

核心问题分析 #

通过日志对比可以明确：

1. 异常触发时机：请求已完全处理并返回200后，客户端提前发送FIN关闭连接，而Kestrel仍尝试复用该长连接读取下一个请求的请求体，导致读取失败抛出异常。
2. 异常无法捕获原因：该异常属于Kestrel底层连接处理阶段的错误，不在ASP.NET Core请求处理管道范围内，因此自定义异常中间件无法拦截。

解决建议 #

一、客户端（PHP Curl）侧调整 #

• 禁用长连接复用：在Curl请求中添加Connection: close请求头，或设置Curl选项CURLOPT_FORBID_REUSE => true，确保客户端收到响应后立即关闭连接，避免Kestrel等待下一个请求。
  示例代码：

  $curl = curl_init();
  curl_setopt($curl, CURLOPT_URL, "你的API地址");
  curl_setopt($curl, CURLOPT_HTTPHEADER, array('Connection: close'));
  // 其他Curl配置项
  $response = curl_exec($curl);
  curl_close($curl);
  

• 确保资源正确释放：避免在curl_exec后立即销毁Curl资源，等待响应完全接收后再执行curl_close。

二、服务器（.NET 6）侧调整 #

• 强制关闭长连接：添加全局中间件，对所有响应注入Connection: close头，主动告知客户端不要复用连接：

  app.Use(async (context, next) =>
  {
      context.Response.Headers.Connection = "close";
      await next();
  });
  

• 过滤无关异常日志：如果不需要监控这类不影响业务的异常，可在appsettings.json中调整日志级别，过滤该特定异常：

  {
    "Logging": {
      "LogLevel": {
        "Microsoft.AspNetCore.Server.Kestrel.Core.BadHttpRequestException": "Warning"
      }
    }
  }
  

• 缩短连接空闲超时：配置Kestrel的连接空闲超时，减少等待下一个请求的时长：

  builder.WebHost.ConfigureKestrel(options =>
  {
      options.Limits.IdleTimeout = TimeSpan.FromSeconds(30);
  });
  

内容的提问来源于stack exchange，提问作者Andreas Andersson