如何调试未被UseDeveloperExceptionPage捕获的.NET 500异常

问题描述 #

运行在容器中的.NET服务出现以下异常现象：

• 调用同一接口时，请求交替出现成功与500失败，后续转为随机失败模式
• 输出窗口抛出System.UriFormatException和System.Net.Http.HttpRequestException异常
• 添加UseDeveloperExceptionPage未捕获到异常，首个中间件断点从未捕获到失败请求，推测问题出在Kestrel层面
• 通过localhost（Swagger）访问无异常，但使用Docker域名（proxy_backend）访问时出现问题

当前Program.cs配置：

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();
builder.Services.AddHealthChecks();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
    app.UseSwagger();
    app.UseSwaggerUI();
}

// Should be the first middleware
app.UseHealthChecks("/HealthCheck");

app.UseRouting();

app.UseEndpoints(endpoints =>
{
    endpoints.Map("/{**catch-all}", async httpContext =>
    {
        // return 200 if we are healthy here
        httpContext.Response.StatusCode = 404;
        return;
    });
});

Console.WriteLine("Test Version 6");

app.Run();

public partial class Program { } // so you can reference it from tests

补充日志 #

Swagger正常请求日志

info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
    Request starting HTTP/1.1 GET http://localhost:50182/category_1a1a1a1a%2Fproduct_2a2a2a2a%2Fid_1123467.product?sig=EEF7952F7B823B6981A797AAE429DF - -
trce: Microsoft.AspNetCore.HostFiltering.HostFilteringMiddleware[2]
    All hosts are allowed.
dbug: Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware[3]
    The request path  does not match the path filter
dbug: Microsoft.AspNetCore.Routing.Matching.DfaMatcher[1001]
    1 candidate(s) found for the request path '/category_1a1a1a1a%2Fproduct_2a2a2a2a%2Fid_1123467.product?sig=EEF7952F7B823B6981A797AAE429DF'
dbug: Microsoft.AspNetCore.Routing.Matching.DfaMatcher[1005]
    Endpoint '/{**catch-all}' with route pattern '/{**catch-all}' is valid for the request path '/category_1a1a1a1a%2Fproduct_2a2a2a2a%2Fid_1123467.product?sig=EEF7952F7B823B6981A797AAE429DF'
dbug: Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware[1]
    Request matched endpoint '/{**catch-all}'
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
    Executing endpoint '/{**catch-all}'
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
    Executed endpoint '/{**catch-all}'
dbug: Microsoft.AspNetCore.Server.Kestrel.Connections[9]
    Connection id "0HMJER5USLLOE" completed keep alive response.
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
    Request finished HTTP/1.1 GET http://localhost:50182/category_1a1a1a1a%2Fproduct_2a2a2a2a%2Fid_1123467.product?sig=EEF7952F7B823B6981A797AAE429DF - - - 404 0 - 3126.3906ms
The thread 0xf12 has exited with code 0 (0x0).
The thread 0xf0f has exited with code 0 (0x0).
The thread '.NET ThreadPool Worker' (0xb2) has exited with code 0 (0x0).
The thread '.NET ThreadPool Worker' (0xbf) has exited with code 0 (0x0).
The thread '.NET ThreadPool Worker' (0xc1) has exited with code 0 (0x0).
The thread '.NET ThreadPool Worker' (0xb8) has exited with code 0 (0x0).
The thread 0xf14 has exited with code 0 (0x0).
The thread 0xf15 has exited with code 0 (0x0).
The thread 0xf10 has exited with code 0 (0x0).

浏览器首次正常请求日志

dbug: Microsoft.AspNetCore.Server.Kestrel.Connections[39]
    Connection id "0HMJER5USLLOF" accepted.
dbug: Microsoft.AspNetCore.Server.Kestrel.Connections[1]
    Connection id "0HMJER5USLLOF" started.
info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
    Request starting HTTP/1.0 GET http://proxy_backend/category_1a1a1a1a/product_2a2a2a2a/id_1123467.product?sig=EEF7952F7B823B6981A797AAE429DF - -
trce: Microsoft.AspNetCore.HostFiltering.HostFilteringMiddleware[2]
    All hosts are allowed.
dbug: Microsoft.AspNetCore.StaticFiles.StaticFileMiddleware[3]
    The request path  does not match the path filter
dbug: Microsoft.AspNetCore.Routing.Matching.DfaMatcher[1001]
    1 candidate(s) found for the request path '/category_1a1a1a1a/product_2a2a2a2a/id_1123467.product'
dbug: Microsoft.AspNetCore.Routing.Matching.DfaMatcher[1005]
    Endpoint '/{**catch-all}' with route pattern '/{**catch-all}' is valid for the request path '/category_1a1a1a1a/product_2a2a2a2a/id_1123467.product'
dbug: Microsoft.AspNetCore.Routing.EndpointRoutingMiddleware[1]
    Request matched endpoint '/{**catch-all}'
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
    Executing endpoint '/{**catch-all}'
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
    Executed endpoint '/{**catch-all}'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
    Request finished HTTP/1.0 GET http://proxy_backend/category_1a1a1a1a/product_2a2a2a2a/id_1123467.product?sig=EEF7952F7B823B6981A797AAE429DF - - - 404 0 - 1959.3089ms
dbug: Microsoft.AspNetCore.Server.Kestrel.Connections[10]
    Connection id "0HMJER5USLLOF" disconnecting.
dbug: Microsoft.AspNetCore.Server.Kestrel.Connections[2]
    Connection id "0HMJER5USLLOF" stopped.
dbug: Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets[7]
    Connection id "0HMJER5USLLOF" sending FIN because: "The Socket transport's send loop completed gracefully."
dbug: Microsoft.AspNetCore.Server.Kestrel.Transport.Sockets[6]
    Connection id "0HMJER5USLLOF" received FIN.

浏览器失败请求日志

Exception thrown: 'System.UriFormatException' in System.Private.Uri.dll
Exception thrown: 'System.UriFormatException' in System.Private.CoreLib.dll
Exception thrown: 'System.UriFormatException' in System.Private.CoreLib.dll

错误根源分析 #

1. HTTP版本与URI编码差异：Swagger请求使用HTTP/1.1且路径经过URL编码（%2F），而Docker域名请求使用HTTP/1.0且路径为原始斜杠。Kestrel对HTTP/1.0请求的URI解析逻辑存在差异，未编码的特殊字符可能触发UriFormatException。
2. 连接复用异常：交替/随机失败模式与连接复用（Keep-Alive）相关，首次连接建立正常，复用连接时后续请求的URI解析出错，导致请求未进入中间件就失败。
3. Docker网络请求格式问题：Docker域名访问时的请求可能存在格式不规范（如HTTP头缺失、路径编码不一致），引发Kestrel解析失败。

调试与解决步骤 #

调试方法 #

• 启用Kestrel详细日志：在appsettings.json中添加日志配置，查看请求解析阶段的详细错误：

  {
    "Logging": {
      "LogLevel": {
        "Microsoft.AspNetCore.Server.Kestrel": "Trace",
        "Microsoft.AspNetCore.Server.Kestrel.Core": "Trace"
      }
    }
  }
  

• 捕获Kestrel连接异常：在Program.cs中注册Kestrel异常回调，直接捕获请求解析阶段的错误：

  builder.WebHost.ConfigureKestrel(serverOptions =>
  {
      serverOptions.OnConnection(connection =>
      {
          connection.ConnectionClosed.Register(() =>
          {
              var errorFeature = connection.Features.Get<Microsoft.AspNetCore.Server.Kestrel.Core.Features.IKestrelConnectionErrorFeature>();
              if (errorFeature?.Error != null)
              {
                  Console.WriteLine($"Kestrel Connection Error: {errorFeature.Error}");
              }
          });
          return Task.CompletedTask;
      });
  });
  

• 模拟异常请求：用curl发送HTTP/1.0请求复现问题：

  curl -v --http1.0 http://proxy_backend/category_1a1a1a1a/product_2a2a2a2a/id_1123467.product?sig=EEF7952F7B823B6981A797AAE429DF
  

解决方案 #

1. 统一HTTP版本与路径编码：确保Docker侧请求使用HTTP/1.1，并对路径中的斜杠进行URL编码（%2F），避免Kestrel解析错误。
2. 配置Kestrel URI解析规则：在Program.cs中调整Kestrel配置，允许未编码路径字符：

   builder.WebHost.ConfigureKestrel(serverOptions =>
   {
       serverOptions.ConfigureEndpointDefaults(listenOptions =>
       {
           listenOptions.NoDelay = true;
           // 调整请求行大小限制，允许更长路径
           serverOptions.Limits.MaxRequestLineSize = 8192;
       });
   });
   

3. 检查Docker代理配置：若使用反向代理（如Nginx），确保代理传递的Host头、路径编码格式正确，避免请求格式失真。

内容的提问来源于stack exchange，提问作者Meir