How to debug .net 500 that not catched by UseDeveloperExceptionPage - asp.net

Question

I have a .net service that runs in a container.
When I run it I have a very wired issue.
Assuming I have the link HTTP//:www.a.com/page.
The first attempt to call HTTP//:www.a.com/page succeeds, the second failed with 500, the third succeeded again, and so on.
In the output window, I can find: Exception thrown: 'System.UriFormatException' in System.Private.Uri.dll and Exception thrown: 'System.Net.Http.HttpRequestException'.
Initially, I thought that all the odd requests succeeded, but then more random patterns started to appear.
I tried to wait a few random seconds between attempts but it did not solve the issue.
Basically, some of the requests succeeded and some did not (again they are all exactly the same requests).
I added UseDeveloperExceptionPage. but it didn't catch anything, I added a BP on my first middleware, the requests that succeed break in it, the 500 never reach that point.
This led me to think that something is rung with Kerstel himself.
I returning 404 on the path, maybe Kerstel has caching mechanized that return automatically 500 if I repeat asking for a 404 path under x minutes?
The question is, how can I debug it? Where is the source of this bug?
This is the current setup of the Program.cs file:
var builder = WebApplication.CreateBuilder(args);
// Add services to the container.
builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
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
-- edit --
When I use localhost (swagger) to communicate with .net, there is no error, only when I use it through the docker naming (using a regular browser request) there is an error, here are the traces:
Trace of swagger request (return 404 as expected):
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).
Trace of browser request (return 404 as expected but with wired failures):
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.
Then the trace of the next browser request (return 500 - failure):
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
It looks like everything is normal when I access .net using http://localhost:50182/ but when I access it from http://proxy_backend (the docker name) only then I get the issues