Proxy doesn't proxy to new implementations GET but keeps going to fallback

[HugoVG]

I've been stuck on a problem, I currently host YARP inside the new Application that is going to constrict the old application, I want everything that isn't found inside the new implementation to fallback to the old app, and incrementally move the code, but I've been running into some issues where GET's won't work in the new application and will always be send to the fallback, even if the GET is in the same controller as one with a POST, the POST works and routes fine, the GET will end up getting send to the OLD one.

I've tried a couple configuration, but I can't seem to get a working correctly with any

Configuration that works most of the time

"ReverseProxy": {
    "Clusters": {
        "cluster1": {
            "Destinations": {
                "destination1": {
                    "Address": "https://OldApplicaion.com"
                }
            }
        }
    }
}

Program.cs

//Program.cs

builder.Services.AddReverseProxy().LoadFromConfig(builder.Configuration.GetSection("ReverseProxy"));
builder.Services.AddControllers();
builder.Services.AddEndpointsApiExplorer();
// ...
app.UseStaticFiles();

app.UseRouting();
// ...
app.UseSystemWebAdapters();

app.MapControllers();
app.UseSoapService();
app.MapDefaultEndpoints();

app.MapReverseProxy();

app.Run();

[HugoVG]

Alternatively, is there a way I could retry to a different cluster I attempted

public async Task InvokeAsync(HttpContext context, RequestDelegate next)
    {
        if(context.Response.HasStarted) return;
        var error = await _httpForwarder.SendAsync(context, "https://localhost:7114", _httpClient, _requestOptions);
        if (error == ForwarderError.None && context.Response.StatusCode != StatusCodes.Status404NotFound)
        {
            return;
        }
        error = await _httpForwarder.SendAsync(context, "https://localhost:9114", _httpClient, _requestOptions);
        if (error != ForwarderError.None || context.Response.StatusCode == StatusCodes.Status404NotFound)
        {
            context.Response.StatusCode = StatusCodes.Status404NotFound;
        }
    }

But it isn't possible because the request has already started and such throws an error.

[MihaZupan]

What does your route configuration look like?
It sounds like this might just be an ordering problem where the YARP route is picked over other controllers.
You can modify its priority by e.g.

"Match": {
  "Path": "{**catch-all}"
},
"Order": 1000000 // Higher = lower priority

You should also try enabling debug ASP.NET logs to observe when and why a given routing decision was made.

If that doesn't solve it, it would be useful if you're able to narrow down the problem to a minimal, runnable, example that reproduces the issue.

Regarding retries, you can read through the discussion in #56. It's not built-in, but possible with some restrictions.

[HugoVG]

My config is in the collapse in the first comment, that's all that is setup and seems to work the best.

I had tried setting Order higher and lower, since it is one endpoint, But I've been trying a lot of things today, but it seems like it is a controller issue out of all things
all my endpoints start with /api/ after removing that it seems to work. I changed a couple controllers to minimal API's and they seem to work just fine without any problem.
Again, for some reason it is just the controllers that are GET

//Controller
[ApiController]
[Route("api/[controller]")]
public class TestController(IService service)  : ControllerBase
{
    [HttpPost("HelloWorld2")] // This works
    [AllowAnonymous]
    public ActionResult<string> PostHelloWorldTest(HelloWorldRequest? request)
    {
        return service.HelloWorldTest(request?.Key);
    }
    [HttpGet("HelloWorld2")] // Trying to reach this one will not resolve and fall back to the cluster1
    [AllowAnonymous]
    public ActionResult<string> GetHelloWorldTest()
    {
        if (HttpContext?.User?.Identity?.IsAuthenticated ==  true)
        {
            return $"¡Hola {HttpContext.User.Identity.Name}!";
        }
        return service.HelloWorldTest();
    }
}

// Program.cs
app.MapGet("/api/test/helloworld", () => "Hello World!"); // this works without problems

[HugoVG]

Well, it seems i have found my issue after half a day, the culprit in question was

[Consumes("application/json")]
[Produces("application/json")]

I might need some coffee☕...