From 980dff05af05a4388b27acc22be9ee420bbeb807 Mon Sep 17 00:00:00 2001
From: katelyn martin <kate@buoyant.io>
Date: Wed, 24 Sep 2025 00:00:00 +0000
Subject: [PATCH] refactor(app/outbound): use `svc::layers()` to apply layers
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we apply a collection of `Layers` to an inner service in our metrics
subsystem. doing so with `layer::mk()` and `Layer::layer()` is somewhat
ungainly.

this commit relies on `svc::layers()` to apply a sequence of telemetry
layers in sequence.

this should have no mechanical difference with the preëxisting code.

Signed-off-by: katelyn martin <kate@buoyant.io>
---
 .../logical/policy/route/backend/metrics.rs   | 30 ++++++++++++-------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/linkerd/app/outbound/src/http/logical/policy/route/backend/metrics.rs b/linkerd/app/outbound/src/http/logical/policy/route/backend/metrics.rs
index 285082ddaa..285d0a89b2 100644
--- a/linkerd/app/outbound/src/http/logical/policy/route/backend/metrics.rs
+++ b/linkerd/app/outbound/src/http/logical/policy/route/backend/metrics.rs
@@ -35,7 +35,7 @@ pub fn layer<T, N>(
             NewResponseDuration<T, ExtractRecordDurationParams<ResponseMetrics<T::StreamLabel>>, N>,
         >,
     >,
-> + Clone
+>
 where
     T: MkStreamLabel,
     N: svc::NewService<T>,
@@ -59,15 +59,25 @@ where
         body_metrics,
     } = metrics.clone();
 
-    svc::layer::mk(move |inner| {
-        use svc::Layer;
-        NewRecordBodyData::layer_via(ExtractRecordBodyDataParams(body_metrics.clone())).layer(
-            NewCountRequests::layer_via(ExtractRequestCount(requests.clone())).layer(
-                NewRecordDuration::layer_via(ExtractRecordDurationParams(responses.clone()))
-                    .layer(inner),
-            ),
-        )
-    })
+    let duration = {
+        let extract = ExtractRecordDurationParams(responses.clone());
+        NewRecordDuration::layer_via(extract)
+    };
+
+    let count_reqs = {
+        let extract = ExtractRequestCount(requests.clone());
+        NewCountRequests::layer_via(extract)
+    };
+
+    let body_data = {
+        let extract = ExtractRecordBodyDataParams(body_metrics.clone());
+        NewRecordBodyData::layer_via(extract)
+    };
+
+    svc::layers()
+        .push(duration)
+        .push(count_reqs)
+        .push(body_data)
 }
 
 #[derive(Clone, Debug)]