Observable FeignContext with immutable Headers

[johnnywiller]

FeignContext enriches the headers providing Propagator.Setter<C> as of Request::header which modifies the headers in place as opposed to make an immutable copy.

In our case the underlining Feign Request is coming with the headers immutable. The headers were created with Collections.unmodifiableMap(headers) by an underlining library which rewrites the request.

Upon trying to enrich the header with the trace ids we face java.lang.UnsupportedOperationException.

Did you encounter this issue before, have you consider not changing headers in place and instead to a immutable copy of the Map<String, Collection<String>> headers; object?

[kdavisk6]

Request is immutable once created. Please use a RequestInterceptor to manipulate headers during the chain.

An alternative is to create a new Request from the previous one, with your updated headers. The older TracingClient demonstrates this approach. See if either of these work for you.