Replace the OTEL-based tracing layer with tracing based layers

crates/tower/src/tracing/make_span.rs

@@ -0,0 +1,72 @@
+// Copyright 2023 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use tracing::Span;
+
+use super::enrich_span::EnrichSpan;
+use crate::utils::FnWrapper;
+
+/// A trait for creating a span for a request.
+pub trait MakeSpan<R> {
+    fn make_span(&self, request: &R) -> Span;
+}
+
+impl<R, F> MakeSpan<R> for FnWrapper<F>
+where
+    F: Fn(&R) -> Span,
+{
+    fn make_span(&self, request: &R) -> Span {
+        (self.0)(request)
+    }
+}
+
+/// Make span from a function.
+pub fn make_span_fn<R, F>(f: F) -> FnWrapper<F>
+where
+    F: Fn(&R) -> Span,
+{
+    FnWrapper(f)
+}
+
+/// A macro to implement [`MakeSpan`] for a tuple of types, where the first type
+/// implements [`MakeSpan`] and the rest implement [`EnrichSpan`].
+macro_rules! impl_for_tuple {
+    (M, $($T:ident),+) => {
+        impl<R, M, $($T),+> MakeSpan<R> for (M, $($T),+)
+        where
+            M: MakeSpan<R>,
+            $($T: EnrichSpan<R>),+
+        {
+            fn make_span(&self, request: &R) -> Span {
+                #[allow(non_snake_case)]
+                let (ref m, $(ref $T),+) = *self;
+
+                let span = m.make_span(request);
+                $(
+                    $T.enrich_span(&span, request);
+                )+
+                span
+            }
+        }
+    };
+}
+
+impl_for_tuple!(M, T1);
+impl_for_tuple!(M, T1, T2);
+impl_for_tuple!(M, T1, T2, T3);
+impl_for_tuple!(M, T1, T2, T3, T4);
+impl_for_tuple!(M, T1, T2, T3, T4, T5);
+impl_for_tuple!(M, T1, T2, T3, T4, T5, T6);
+impl_for_tuple!(M, T1, T2, T3, T4, T5, T6, T7);
+impl_for_tuple!(M, T1, T2, T3, T4, T5, T6, T7, T8);