Swagger 从 YARP 代理服务器访问时显示“无法加载 API 定义”错误

Question

Since ocelot is no longer maintained, I decided to give a go to YARP as my API Gateway but it's giving me this silly error when I access one of my endpoints through it:

  "ReverseProxy": {
    "Routes": {
      "client-route": {
        "ClusterId": "client-cluster",
        "CorsPolicy": "customPolicy",
        "Match": {
          "Path": "client-service/{**remainder}"
        },
        "Transforms": [
          { "X-Forwarded": "Off" },
          {
            "PathPattern": "/{**remainder}"
          }
        ]
      }
    },
    "Clusters": {
      "client-cluster": {
        "Destinations": {
          "destination1": {
            "Address": "https://URLWithSwagger/"
          }
        }
      }
    }
  }

when using the configuration above, I get the following error:

but when I change the path from "client-service/{**remainder}" to "/{**remainder}" , everything works fine? any suggestions on the root of this error?

Update: Here's the program.cs:

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.

builder.Services.AddReverseProxy()//.AddConfigFilter();
    .LoadFromConfig(builder.Configuration.GetSection("ReverseProxy"));

var app = builder.Build();

app.UseHttpsRedirection();

app.UseAuthorization();


app.MapReverseProxy();

app.Run();

Answer 1

In your sample, the path client-service/url is forwarded as is to the backend. And such url does not exists. That's why removing the prefix works again.

To fix: you need to transform the url to remove the client-service prefix per route. You can do it with yarp adding the PathRemovePrefix transformer:

"client-route": {
    "ClusterId": "client-cluster",
    "Match": {
      "Path": "/client-service/{****remainder}"
    },
    "Transforms": [
      { "PathRemovePrefix": "/client-service" }
    ]
  },
      

This will work to get the raw swagger Specification (JSON file). If you want to render it on SwaggerUI you should inject SwaggerUI on the reverse-proxy and pass the forwarded contract: openapi.json URI to it.

For more details on this one, see this issue .