swarm-notify-router: give the event duration histogram second-scale bounds

swarm-notify-router/src/metrics.rs

@@ -28,6 +28,13 @@ use opentelemetry_sdk::metrics::SdkMeterProvider;
 
 const METER: &str = "hyperhive.notify_router";
 
+/// Seconds. Handling one event is a few queue and store round trips, in
+/// milliseconds; a review request waits on the controller's answer, up to 30
+/// seconds. The SDK's own bounds start at 5 and are made for milliseconds.
+const DURATION_BOUNDARIES: [f64; 12] = [
+    0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1.0, 2.5, 5.0, 10.0, 30.0,
+];
+
 /// What came of handling one event.
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
 pub enum Handled {
@@ -108,6 +115,7 @@ impl Metrics {
             duration: meter
                 .f64_histogram(format!("{METER}.event.duration"))
                 .with_unit("s")
+                .with_boundaries(DURATION_BOUNDARIES.to_vec())
                 .build(),
             todos: meter.u64_counter(format!("{METER}.todos")).build(),
             reviews: meter