fix last tracing test

reqwest-tracing/src/lib.rs

@@ -62,16 +62,17 @@
 //! use tracing::Span;
 //! use std::time::{Duration, Instant};
 //!
-//! pub struct TimeTrace;
+//! pub struct TimeTrace(Instant);
 //!
 //! impl ReqwestOtelSpanBackend for TimeTrace {
-//!     fn on_request_start(req: &Request, extension: &mut Extensions) -> Span {
-//!         extension.insert(Instant::now());
-//!         reqwest_otel_span!(name="example-request", req, time_elapsed = tracing::field::Empty)
+//!     fn on_request_start(req: &Request, _extension: &mut Extensions) -> (Self, Span) {
+//!         let now = Self(Instant::now());
+//!         let span = reqwest_otel_span!(name="example-request", req, time_elapsed = tracing::field::Empty);
+//!         (now, span)
 //!     }
 //!
-//!     fn on_request_end(span: &Span, outcome: &Result<Response, Error>, extension: &mut Extensions) {
-//!         let time_elapsed = extension.get::<Instant>().unwrap().elapsed().as_millis() as i64;
+//!     fn on_request_end(self, span: &Span, outcome: &Result<Response, Error>) {
+//!         let time_elapsed = self.0.elapsed().as_millis() as i64;
 //!         default_on_request_end(span, outcome);
 //!         span.record("time_elapsed", &time_elapsed);
 //!     }

reqwest-tracing/src/middleware.rs

@@ -47,14 +47,14 @@ where
     fn layer(&self, inner: Svc) -> Self::Service {
         TracingMiddlewareService {
             service: inner,
-            layer: *self,
+            _layer: *self,
         }
     }
 }
 
 /// Middleware Service for tracing requests using the current Opentelemetry Context.
 pub struct TracingMiddlewareService<S: ReqwestOtelSpanBackend, Svc> {
-    layer: TracingMiddleware<S>,
+    _layer: TracingMiddleware<S>,
     service: Svc,
 }
 
@@ -77,7 +77,7 @@ where
             request,
             mut extensions,
         } = req;
-        let request_span = ReqwestOtelSpan::on_request_start(&request, &mut extensions);
+        let (backend, span) = ReqwestOtelSpan::on_request_start(&request, &mut extensions);
         // Adds tracing headers to the given request to propagate the OpenTelemetry context to downstream revivers of the request.
         // Spans added by downstream consumers will be part of the same trace.
         #[cfg(any(
@@ -96,8 +96,8 @@ where
         });
 
         TracingMiddlewareFuture {
-            layer: self.layer,
-            span: request_span,
+            span,
+            backend: Some(backend),
             future,
         }
     }
@@ -105,8 +105,8 @@ where
 
 pin_project!(
     pub struct TracingMiddlewareFuture<S: ReqwestOtelSpanBackend, F> {
-        layer: TracingMiddleware<S>,
         span: Span,
+        backend: Option<S>,
         #[pin]
         future: F,
     }
@@ -123,7 +123,10 @@ impl<S: ReqwestOtelSpanBackend, F: Future<Output = Result<Response, Error>>> Fut
             let _guard = this.span.enter();
             ready!(this.future.poll(cx))
         };
-        S::on_request_end(this.span, &outcome);
+        this.backend
+            .take()
+            .expect("poll should not be called after completion")
+            .on_request_end(this.span, &outcome);
         Poll::Ready(outcome)
     }
 }

reqwest-tracing/src/reqwest_otel_span_builder.rs

@@ -39,12 +39,12 @@ pub const HTTP_USER_AGENT: &str = "http.user_agent";
 /// Check out [`reqwest_otel_span`] documentation for examples.
 ///
 /// [`TracingMiddleware`]: crate::middleware::TracingMiddleware.
-pub trait ReqwestOtelSpanBackend {
+pub trait ReqwestOtelSpanBackend: Sized {
     /// Initalized a new span before the request is executed.
-    fn on_request_start(req: &Request, extension: &mut Extensions) -> Span;
+    fn on_request_start(req: &Request, extension: &mut Extensions) -> (Self, Span);
 
     /// Runs after the request call has executed.
-    fn on_request_end(span: &Span, outcome: &Result<Response, Error>);
+    fn on_request_end(self, span: &Span, outcome: &Result<Response, Error>);
 }
 
 /// Populates default success/failure fields for a given [`reqwest_otel_span!`] span.
@@ -95,15 +95,15 @@ pub fn default_on_request_failure(span: &Span, e: &Error) {
 pub struct DefaultSpanBackend;
 
 impl ReqwestOtelSpanBackend for DefaultSpanBackend {
-    fn on_request_start(req: &Request, ext: &mut Extensions) -> Span {
+    fn on_request_start(req: &Request, ext: &mut Extensions) -> (DefaultSpanBackend, Span) {
         let name = ext
             .get::<OtelName>()
             .map(|on| on.0.as_ref())
             .unwrap_or("reqwest-http-client");
-        reqwest_otel_span!(name = name, req)
+        (Self, reqwest_otel_span!(name = name, req))
     }
 
-    fn on_request_end(span: &Span, outcome: &Result<Response, Error>) {
+    fn on_request_end(self, span: &Span, outcome: &Result<Response, Error>) {
         default_on_request_end(span, outcome)
     }
 }
@@ -119,16 +119,19 @@ fn get_header_value(key: &str, headers: &HeaderMap) -> String {
 pub struct SpanBackendWithUrl;
 
 impl ReqwestOtelSpanBackend for SpanBackendWithUrl {
-    fn on_request_start(req: &Request, ext: &mut Extensions) -> Span {
+    fn on_request_start(req: &Request, ext: &mut Extensions) -> (Self, Span) {
         let name = ext
             .get::<OtelName>()
             .map(|on| on.0.as_ref())
             .unwrap_or("reqwest-http-client");
 
-        reqwest_otel_span!(name = name, req, http.url = %remove_credentials(req.url()))
+        (
+            Self,
+            reqwest_otel_span!(name = name, req, http.url = %remove_credentials(req.url())),
+        )
     }
 
-    fn on_request_end(span: &Span, outcome: &Result<Response, Error>) {
+    fn on_request_end(self, span: &Span, outcome: &Result<Response, Error>) {
         default_on_request_end(span, outcome)
     }
 }

reqwest-tracing/src/reqwest_otel_span_macro.rs

@@ -41,11 +41,11 @@
 /// pub struct CustomReqwestOtelSpanBackend;
 ///
 /// impl ReqwestOtelSpanBackend for CustomReqwestOtelSpanBackend {
-///     fn on_request_start(req: &Request, _extension: &mut Extensions) -> Span {
-///         reqwest_otel_span!(name = "reqwest-http-request", req)
+///     fn on_request_start(req: &Request, _extension: &mut Extensions) -> (Self, Span) {
+///         (Self, reqwest_otel_span!(name = "reqwest-http-request", req))
 ///     }
 ///
-///     fn on_request_end(span: &Span, outcome: &Result<Response, Error>) {
+///     fn on_request_end(self, span: &Span, outcome: &Result<Response, Error>) {
 ///         default_on_request_end(span, outcome)
 ///     }
 /// }