Support OA3 Server Templates

[DaleyKD]

https://swagger.io/docs/specification/api-host-and-base-path/

I'm trying to serve my swagger.json from two locations:

• https://acme.company.com/appName/myTenant/swagger/v1/swagger.json [this is a direct URL to the .json, which lives "under" the application I've written]
• https://gateway.company.com/swagger [the MMLib Swagger UI for Ocelot]

In an attempt to support this, I started using the servers part of the OpenAPI 3 spec. It looks something like this in C#:

new OpenApiServer()
{
    Url = "https://{accountHost}.company.com/appName/{tenantHost}",
    Description = "My Application Direct",
    Variables = new Dictionary<string, OpenApiServerVariable>()
    {
        {
            "accountHost", new OpenApiServerVariable()
            {
                Description = "The hostname of the account.",
                Default = "acme"
            }
        },
        {
            "tenantHost", new OpenApiServerVariable()
            {
                Description = "The hostname of the tenant.",
                Default = "myTenant"
            }
        }
    }
}

Reading in MMLib, I noticed you only support one server for now. That's totally understandable. To get this to semi-work, I then added the server at the 0-index:

new OpenApiServer() {Url = "/{tenantHost}", Description = "My Application via Gateway"}

However, to be a bit more verbose, I'd prefer to use:

new OpenApiServer()
{
    Url = "https://gateway.company.{tld}/{tenantHost}",
    Description = "My Application via Gateway",
    Variables = new Dictionary<string, OpenApiServerVariable>()
    {
            "tld", new OpenApiServerVariable()
            {
                Description = "The environment.",
                Default = "com",
                Enum = new List<string>()
                {
                    "com",
                    "net",
                    "co.uk"
                }
            }
        {
            "tenantHost", new OpenApiServerVariable()
            {
                Description = "The hostname of the tenant.",
                Default = "myTenant"
            }
        }
    }
}

This throws a UriFormatException. It seems like

MMLib.SwaggerForOcelot/src/MMLib.SwaggerForOcelot/Transformation/SwaggerJsonTransformer.cs

Line 78 in 18ea188

private string TransformOpenApi(JObject openApi, IEnumerable<RouteOptions> routes, string serverOverride = "/")

is not designed to support server templates.

[Burgyn]

Hi @DaleyKD,

I'm sorry for late answer.

I will try to explore the possibilities and try to respond within a few days.

[DaleyKD]

Appreciate the consideration!

[Burgyn]

Hi @DaleyKD,

I prepared a new version 4.1.0 with the ability to take over the definition of OpenAPI servers from the downstream service.

Please test if this solves your use case.

---

from docs:

If you have multiple servers defined in the downstream service Open API documentation, or you use server templating and you want to use it on the gateway side as well, then you must explicitly enable it on the Swagger endpoint definition by setting property TakeServersFromDownstreamService to true.

"SwaggerEndPoints": [
    {
      "Key": "users",
      "TakeServersFromDownstreamService": true,
      "Config": [
        {
          "Name": "Users API",
          "Version": "v1",
          "Service": {
            "Name": "users",
            "Path": "/swagger/v1/swagger.json"
          }
        }
      ]
    }
]

⚠ If you set TakeServersFromDownstreamService to true, then the server path is not used to transform the paths of individual endpoints.