Migration path to v3 when using custom IHttpTransformerFactory with YARP extensions

[bamarch]

BFF v3 removes IHttpTransformerFactory, see DuendeSoftware/products#1734

The PR and the upgrade docs recommend using new features of MapRemoteBffApiEndpoint() as a replacement for custom implementations of IHttpTransformerFactory

MapRemoteBffApiEndpoint() is part of the Simple HTTP Forwarder extensions

What is the migration path from v2 to v3 people using YARP extensions and a custom IHttpTransformerFactory?

Use case for the custom implementation is:

• globally removing certain headers from proxied requests
• adding headers to proxied requests that derive from the access token (e.g. idp, user id)

[Erwinvandervalk]

Hi @bamarch,

Thanks for your question. If I recall, the IHttpTransformerFactory was only used when doing direct mapping. It's replacement BffYarpTransformBuilder is also only used for direct mapping.

If you wish to use yarp directly, you can customize what kind of transforms are added by yarp via the ITransformProvider interface. It allows you to (conditionally) add one or more transforms to the pipeline.

If you wish to add headers based on the access token, you may wish to look at these classes:

• AccessTokenTransformProvider. This class demonstrates how to add transforms to your pipeline. It checks if a specific metadata is present and only then adds the transform.

• AccessTokenRequestTransform This transform retrieves the access token and adds it to the request. You could do something similar to add specific headers based on information in the access token. Since the access token is cached, you should be able to retrieve the access token multiple times.

Hope this helps,

Erwin

[bamarch]

Ok will use YARP ITransformProvider, thanks

[Erwinvandervalk]

Great, please let me know if you run into trouble!

[bamarch]

The two links you provided were really helpful, got it all sorted as you suggested, thanks again!