Function trace

pub fn trace<S, Req, I, F>(
    service_factory: I,
    make_span: F,
) -> ApplyTransform<TracingTransform<S::Service, S, F>, S, Req>
where
    I: IntoServiceFactory<S, Req>,
    S: ServiceFactory<Req>,
    F: Fn(&Req) -> Option<Span> + Clone,

Wraps the provided service factory with a transform that automatically enters/exits the given span.

The span to be entered/exited can be provided via a closure. The closure is passed in a reference to the request being handled by the service.

For example:

let traced_service = trace(
    web_service,
    |req: &Request| Some(span!(Level::INFO, "request", req.id))
);