How to add placeholder value to header?

[ELymar]

Expected Behavior / New Feature

I need to take a part of the route like api/subscriber/{guid} and create a header value that gets passed to the downstream services.

I'm trying to do the following as part of PreQueryStringBuilderMiddleware:

var subscriber = context.TemplatePlaceholderNameAndValues?.FirstOrDefault(p => p.Name == "{guid}")?.Value;
context.HttpContext.Request.Headers.Add("Subscriber", new Microsoft.Extensions.Primitives.StringValues(subscriber)); 
await next.Invoke();

I've also tried this with no luck:

  "ReRoutes": [
    {
      "UpstreamPathTemplate": "/api/subscribers/{subscriberId}/widgets",
      "DownstreamScheme": "http",
      "DownstreamPathTemplate": "/api/widgets",
      "UpstreamHttpMethod": [ "Get", "Post" ],
      "ServiceName": "WidgetsUnlimited/WidgetService",
      "UpstreamHeaderTransform": {
        "SubscriberId":  "{subscriberId}"
      },
      "AuthenticationOptions": {
        "AuthenticationProviderKey": "KeyForAuth",
        "AllowedScopes": [ "openflows-watersight" ],
        "QoSOptions": {
          "TimeoutValue": 360000
        }
      }
    },

Actual Behavior / Motivation for New Feature

I don't see the header in the context of the request at the downstream controller. Is there another way to achieve this?

Specifications

• Version: 15.0.6
• Platform: Windows 10
• Subsystem: ASP.NET Core

[rh101]

Try the solution described here: #1267 (comment)

[raman-m]

Why did you want to convert placeholder to a header? What's the goal?
Why not to use classic Placeholders logic to convert to query parameter and reuse it in downstream service?

  "Routes": [
    {
      "UpstreamPathTemplate": "/api/subscribers/{subscriberId}/widgets",
      "DownstreamPathTemplate": "/api/widgets?subscriber={subscriberId}", // <<<--- your solution
      // redundant now
      "UpstreamHeaderTransform": {
        "SubscriberId":  "{subscriberId}"
      },
    },

You have to understand that by limitations our current Header Transform Placeholders logic supports only system predefined placeholders, but not placeholders from path templates... But Yes, it makes sense to have them in transformations too.