From e888d7ec5a4f9330196ee1bb69eff902314ff8b3 Mon Sep 17 00:00:00 2001
From: Alpcan Ornek <alpcan0708@gmail.com>
Date: Thu, 21 May 2026 10:28:06 +0200
Subject: [PATCH 1/2] fix(hedge): assert non-zero rotation period on
 construction

---
 tower/src/hedge/mod.rs    |  9 +++++++++
 tower/tests/hedge/main.rs | 23 +++++++++++++++++++++++
 2 files changed, 32 insertions(+)

diff --git a/tower/src/hedge/mod.rs b/tower/src/hedge/mod.rs
index 9698a9b7d..40cb124a8 100644
--- a/tower/src/hedge/mod.rs
+++ b/tower/src/hedge/mod.rs
@@ -97,6 +97,10 @@ impl<S, P> Hedge<S, P> {
         S::Error: Into<crate::BoxError>,
         P: Policy<Request> + Clone,
     {
+        assert!(
+            period > Duration::ZERO,
+            "histogram rotation period must be greater than zero"
+        );
         let histo = Arc::new(Mutex::new(RotatingHistogram::new(period)));
         Self::new_with_histo(service, policy, min_data_points, latency_percentile, histo)
     }
@@ -116,6 +120,11 @@ impl<S, P> Hedge<S, P> {
         S::Error: Into<crate::BoxError>,
         P: Policy<Request> + Clone,
     {
+        assert!(
+            period > Duration::ZERO,
+            "histogram rotation period must be greater than zero"
+        );
+
         let histo = Arc::new(Mutex::new(RotatingHistogram::new(period)));
         {
             let mut locked = histo.lock().unwrap();
diff --git a/tower/tests/hedge/main.rs b/tower/tests/hedge/main.rs
index d4082ca2a..7448eeeee 100644
--- a/tower/tests/hedge/main.rs
+++ b/tower/tests/hedge/main.rs
@@ -182,3 +182,26 @@ fn new_service<P: Policy<Req> + Clone>(policy: P) -> (mock::Spawn<Hedge<Mock, P>
 
     (mock::Spawn::new(service), handle)
 }
+
+#[test]
+#[should_panic(expected = "histogram rotation period must be greater than zero")]
+fn hedge_new_with_mock_latencies_zero_period_panics() {
+    let (service, _handle) = tower_test::mock::pair::<Req, Res>();
+    let mock_latencies: [u64; 2] = [10, 20];
+
+    let _service = Hedge::new_with_mock_latencies(
+        service,
+        TestPolicy,
+        10,
+        0.9,
+        Duration::ZERO,
+        &mock_latencies,
+    );
+}
+#[test]
+#[should_panic(expected = "histogram rotation period must be greater than zero")]
+fn hedge_new_zero_period_panics() {
+    let (service, _handle) = tower_test::mock::pair::<Req, Res>();
+
+    let _service = Hedge::new(service, TestPolicy, 10, 0.9, Duration::ZERO);
+}

From 05446845a46f5596b295b8c57e1d0ab7b77e2219 Mon Sep 17 00:00:00 2001
From: Alpcan Ornek <alpcan0708@gmail.com>
Date: Thu, 21 May 2026 16:35:35 +0200
Subject: [PATCH 2/2] docs(hedge): add explicit # Panics section to constructor

---
 tower/src/hedge/mod.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tower/src/hedge/mod.rs b/tower/src/hedge/mod.rs
index 40cb124a8..41276552d 100644
--- a/tower/src/hedge/mod.rs
+++ b/tower/src/hedge/mod.rs
@@ -85,6 +85,10 @@ pub struct SelectPolicy<P> {
 
 impl<S, P> Hedge<S, P> {
     /// Create a new hedge middleware.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `period` is zero.
     pub fn new<Request>(
         service: S,
         policy: P,