We're using Brave's ExtraFieldPropagation feature to propagate custom fields (e.g. an internal-only request identifier) between services as HTTP headers.
Some of our services make requests to external services using a RestTemplate or Feign client in the course of processing a request. Since Sleuth enhances all RestTemplate beans and Feign clients with the propagation feature, this means that external services receive the internal-only headers, which I'd like to avoid.
I know of two workarounds that allow me to avoid this behavior, both of which are flawed:
@Bean so that Sleuth does not add an interceptor. The downside I see here is that developers have to remember to follow this pattern to avoid leaking information, and this is difficult to enforce.RestTemplate and Feign clients (not a huge deal); b) it looks like Feign client interceptors do not have a way to influence order of execution (see javadoc here), so I can't guarantee that the new interceptor will run last / after the Sleuth one.Is there a way to customize Sleuth (e.g. via some kind of injector bean) such that, prior to injecting headers in an outgoing HTTP request, I can reason about the destination of the request? I saw documentation regarding custom injector beans, but it appears those no longer exist in spring boot >= 2. I can't seem to find an equivalent construct in Brave.
You can unsample a given URL which means that the headers will be propagated but not sent to Zipkin. You can't disable instrumentation for only some of the URLs cause we're instrumenting all of the components that are registered as beans.