v0.34.0_1

src/metrics/vhost.rs

@@ -62,12 +62,25 @@ impl VhostMetrics {
                 Err(observed) => current = observed,
             }
         }
-        for (index, threshold) in DURATION_BUCKETS_US.iter().enumerate() {
-            if micros <= *threshold {
-                self.buckets[index].fetch_add(1, Ordering::Relaxed);
+        // Write exactly one exclusive histogram bin per exchange. Prometheus
+        // cumulative le=... buckets are reconstructed only when scraped.
+        // This removes up to 11 contended atomics for short 1 KiB responses.
+        let bucket = DURATION_BUCKETS_US.partition_point(|threshold| micros > *threshold);
+        self.buckets[bucket].fetch_add(1, Ordering::Relaxed);
+    }
+
+    /// A scrape-consistent cumulative representation of exclusive bins. The
+    /// sum of atomic snapshots is monotonic and the final count includes +Inf.
+    pub fn duration_histogram(&self) -> ([u64; DURATION_BUCKETS_US.len()], u64) {
+        let mut cumulative = [0u64; DURATION_BUCKETS_US.len()];
+        let mut count = 0u64;
+        for (index, bin) in self.buckets.iter().enumerate() {
+            count = count.saturating_add(bin.load(Ordering::Relaxed));
+            if index < DURATION_BUCKETS_US.len() {
+                cumulative[index] = count;
             }
         }
-        self.buckets[DURATION_BUCKETS_US.len()].fetch_add(1, Ordering::Relaxed);
+        (cumulative, count)
     }
 
     pub fn view(&self) -> VhostMetricsView {