Better support for request-specific headers

This is more of a question than an issue, but there is no mailing list for Feign that I could find.

From what I can tell, feign does not support request-specific headers unless they are declared as a method parameter. This is problematic from the standpoint of incorporating Feign into a set of stateless web services as a singleton bean, and wanting to optionally forward a set of headers from service to service without having the client explicitly have to deal with them.

It seems that creating feign clients per-request could be a performance concern since reflection is used to generate the proxy. I couldn't find anywhere in the Feign builder infrastructure which caches the reflected object state to improve the performance of repeated builds of the same interface with minor adjustments to the builder object.

Has any thought been put into either adding some mechanism for allowing modifications to a specific request before sending it, or reducing the cost of creating Feign instances? Either of these approaches would help me achieve my goal. The first suggestion could potentially dovetail with the ticket for asynchronous requests that I saw on the board.

Thanks,
Chad

Start by reading the Feign builder infrastructure and the request-construction path mentioned in the issue. Compare the two proposed directions: request-specific header modification and reducing the cost of repeatedly creating clients. Done would require an agreed scope, an implemented approach, and tests covering the selected behavior.