From 8bc962e1ee351669e2b0237d1a2add43a67cd98e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Thu, 23 Oct 2025 18:08:11 -0300
Subject: [PATCH 1/3] refactor: remove Mutex from `FunctionProfilingLayer`

---
 cmd/ethrex/initializers.rs             |  2 +-
 crates/blockchain/metrics/profiling.rs | 22 ++++++++++------------
 2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/cmd/ethrex/initializers.rs b/cmd/ethrex/initializers.rs
index 839e7fc7508..5d98cd7e0b9 100644
--- a/cmd/ethrex/initializers.rs
+++ b/cmd/ethrex/initializers.rs
@@ -65,7 +65,7 @@ pub fn init_tracing(opts: &Options) -> reload::Handle<EnvFilter, Registry> {
     let fmt_layer = layer.with_filter(filter);
 
     let subscriber: Box<dyn tracing::Subscriber + Send + Sync> = if opts.metrics_enabled {
-        let profiling_layer = FunctionProfilingLayer::default();
+        let profiling_layer = FunctionProfilingLayer;
         Box::new(Registry::default().with(fmt_layer).with(profiling_layer))
     } else {
         Box::new(Registry::default().with(fmt_layer))
diff --git a/crates/blockchain/metrics/profiling.rs b/crates/blockchain/metrics/profiling.rs
index 01af686fd91..1a4bd3b03b4 100644
--- a/crates/blockchain/metrics/profiling.rs
+++ b/crates/blockchain/metrics/profiling.rs
@@ -1,8 +1,5 @@
 use prometheus::{Encoder, HistogramTimer, HistogramVec, TextEncoder, register_histogram_vec};
-use std::{
-    collections::HashMap,
-    sync::{LazyLock, Mutex},
-};
+use std::sync::LazyLock;
 use tracing::{Subscriber, span::Id};
 use tracing_subscriber::{Layer, layer::Context, registry::LookupSpan};
 
@@ -23,9 +20,9 @@ fn initialize_histogram_vec() -> HistogramVec {
 // We use this struct to simplify accumulating the time spent doing each task and publishing the metric only when the sync cycle is finished
 // We need to do this because things like database reads and writes are spread out throughout the code, so we need to gather multiple measurements to publish
 #[derive(Default)]
-pub struct FunctionProfilingLayer {
-    function_timers: Mutex<HashMap<Id, HistogramTimer>>,
-}
+pub struct FunctionProfilingLayer;
+
+struct ProfileTimer(HistogramTimer);
 
 impl<S> Layer<S> for FunctionProfilingLayer
 where
@@ -40,14 +37,15 @@ where
             let timer = METRICS_BLOCK_PROCESSING_PROFILE
                 .with_label_values(&[name])
                 .start_timer();
-            let mut timers = self.function_timers.lock().unwrap();
-            timers.insert(id.clone(), timer);
+            span.extensions_mut().insert(ProfileTimer(timer));
         }
     }
 
-    fn on_exit(&self, id: &Id, _ctx: Context<'_, S>) {
-        let mut timers = self.function_timers.lock().unwrap();
-        if let Some(timer) = timers.remove(id) {
+    fn on_exit(&self, id: &Id, ctx: Context<'_, S>) {
+        let timer = ctx
+            .span(id)
+            .and_then(|span| span.extensions_mut().remove::<ProfileTimer>());
+        if let Some(ProfileTimer(timer)) = timer {
             timer.observe_duration();
         }
     }

From 76da36da6079e56d04d23d577e80c842ff283bea Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Thu, 23 Oct 2025 18:09:18 -0300
Subject: [PATCH 2/3] docs: add comment

---
 crates/blockchain/metrics/profiling.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/crates/blockchain/metrics/profiling.rs b/crates/blockchain/metrics/profiling.rs
index 1a4bd3b03b4..f1a181234f0 100644
--- a/crates/blockchain/metrics/profiling.rs
+++ b/crates/blockchain/metrics/profiling.rs
@@ -37,6 +37,7 @@ where
             let timer = METRICS_BLOCK_PROCESSING_PROFILE
                 .with_label_values(&[name])
                 .start_timer();
+            // PERF: `extensions_mut` uses a Mutex internally (per span)
             span.extensions_mut().insert(ProfileTimer(timer));
         }
     }
@@ -44,6 +45,7 @@ where
     fn on_exit(&self, id: &Id, ctx: Context<'_, S>) {
         let timer = ctx
             .span(id)
+            // PERF: `extensions_mut` uses a Mutex internally (per span)
             .and_then(|span| span.extensions_mut().remove::<ProfileTimer>());
         if let Some(ProfileTimer(timer)) = timer {
             timer.observe_duration();

From d632d6e028338211877629c993919e568bae0208 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1s=20Gr=C3=BCner?=
 <47506558+MegaRedHand@users.noreply.github.com>
Date: Thu, 23 Oct 2025 18:14:10 -0300
Subject: [PATCH 3/3] docs: add documentation on newtype

---
 crates/blockchain/metrics/profiling.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/crates/blockchain/metrics/profiling.rs b/crates/blockchain/metrics/profiling.rs
index f1a181234f0..cd90977d365 100644
--- a/crates/blockchain/metrics/profiling.rs
+++ b/crates/blockchain/metrics/profiling.rs
@@ -22,6 +22,7 @@ fn initialize_histogram_vec() -> HistogramVec {
 #[derive(Default)]
 pub struct FunctionProfilingLayer;
 
+/// Wrapper around [`HistogramTimer`] to avoid conflicts with other layers
 struct ProfileTimer(HistogramTimer);
 
 impl<S> Layer<S> for FunctionProfilingLayer