How to match a file name and non-file name in appsettings.json?

[zwcloud]

• File name requests will be handled by file-cluster serving static files.
• Non file name requests, namely API requests will be handled by api-cluster running WebAPI.

  "ReverseProxy": {
    "Routes": {
      "route0": {
        "ClusterId": "file-cluster",
        "Match": {
          "Path": "**filename**"
        }
      },
      "route1": {
        "ClusterId": "api-cluster",
        "Match": {
          "Path": "**api**"
        }
      }
    },
    "Clusters": {
      "file-cluster": {
        "Destinations": {
          "destination1": {
            "Address": "http://127.0.0.1:8080/"
          }
        }
      },
      "api-cluster": {
        "Destinations": {
          "destination1": {
            "Address": "http://127.0.0.1:8081/"
          }
        }
      }
    }

How to fill **filename** and **api**?

If it isn't possible, how to override the default behavior? I mean something like

//maybe in some middleware?
if(filenameRegex.IsMatch(context.Request.Path)){
    UseCluster("file-cluster");
}
else{
    UseCluster("api-cluster");
}

Update:
Just tried

var apiRegex = new Regex(@"^[a-zA-Z0-9/]+$");
app.Use(async (context, next) =>
{
    var path = context.Request.Path.Value;
    var isIndex = path is null or "" or "/";
    var isApi = !isIndex && apiRegex.IsMatch(path);
    context.ReassignProxyRequest(new ClusterState(isApi ? "api_cluster" : "file_cluster"));
    await next();
});

But it throws System.InvalidOperationException: Yarp.ReverseProxy.Model.IReverseProxyFeature is missing. at context.ReassignProxyRequest:

System.InvalidOperationException: Yarp.ReverseProxy.Model.IReverseProxyFeature is missing.
   at Microsoft.AspNetCore.Http.HttpContextFeaturesExtensions.GetReverseProxyFeature(HttpContext context)
   at Microsoft.AspNetCore.Http.HttpContextFeaturesExtensions.ReassignProxyRequest(HttpContext context, ClusterState cluster)

Is it a bug or I did something wrong?

[zwcloud]

Done. Followed the example in https://github.com/microsoft/reverse-proxy/blob/main/docs/docfx/articles/ab-testing.md

here is the solution:

IProxyStateLookup lookup = app.Services.GetRequiredService<IProxyStateLookup>();
var apiRegex = new Regex(@"^[a-zA-Z0-9/]+$");
string ChooseCluster(HttpContext context)
{
    var path = context.Request.Path.Value;
    var isIndex = path is null or "" or "/";
    var isApi = !isIndex && apiRegex.IsMatch(path);
    // Decide which cluster to use. This could be random, weighted, based on headers, etc.
    return isApi ? "api_cluster" : "file_cluster";
}

app.MapReverseProxy(proxyPipeline => {
    // Custom cluster selection
    proxyPipeline.Use(async (context, next) =>
    {
        if(lookup.TryGetCluster(ChooseCluster(context), out var cluster))
        {
            context.ReassignProxyRequest(cluster);
        }
        await next();
    });
});

And the settings:

  "ReverseProxy": {
    "Routes": {
      "route1": {
        "ClusterId": "file_cluster",
        "Match": {
          "Path": "{**catch-all}"
        }
      }
    },
    "Clusters": {
      "file_cluster": {
        "Destinations": {
          "destination1": {
            "Address": "http://127.0.0.1:8080/"
          }
        }
      },
      "api_cluster": {
        "Destinations": {
          "destination1": {
            "Address": "http://127.0.0.1:8081/"
          }
        }
      }
    }
  }

Note a dummy Route must be added in the settings, otherwise context.ReassignProxyRequest won't be called.

[Tratcher]

Glad that worked for you.

FYI you can also use regexes directly in the Match Path field.
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/routing?view=aspnetcore-7.0#regular-expressions-in-constraints