Redirecting based on a condition

[jongallant]

Hey, just curious if I am missing something obvious. I am attempting run custom validation in a middleware, and then if certain conditions are met to redirect to a different destination than requested.

Essentially what I am trying to do is perform a response redirect, so that the user is directed to a different location.

What is the way to do this correctly with YARP? Am I forced to use Direct Forwarding?

[MihaZupan]

There's a context.ReassignProxyRequest(cluster) API you can use to change the destination in a middleware.
See https://microsoft.github.io/reverse-proxy/articles/ab-testing.html

[jongallant]

Hey thanks. I am not trying to send it to a different cluster, just a different resource on the same cluster.

[MihaZupan]

You have a few options.

• Since you're in a middleware already, you could just short-circuit the response and return a redirect, forcing the client to fetch it again.
• If you just want to modify just the path, you can alter the httpContext.Request and let YARP proxy to that resource instead.
• The cleanest option may be to just do this in a request transform

  services.AddReverseProxy()
      .AddTransforms(transformBuilderContext =>
      {
          transformBuilderContext.AddRequestTransform(async context =>
          {
              if (await MyConditionAsync(context))
              {
                  var newUri = new UriBuilder(context.ProxyRequest.RequestUri);
                  newUri.Path = "/something";
                  context.ProxyRequest.RequestUri = newUri.Uri;
              }
          });
      })