internal/metrics/metrics.go

@@ -384,6 +384,7 @@ func (s *Set) initSeries() {
 		s.deliveriesFailed.WithLabelValues(label)
 		s.deliveryRetries.WithLabelValues(label)
 		s.deliveryReplays.WithLabelValues(label)
+		s.deliveryDuration.WithLabelValues(label)
 		s.deliveriesPending.WithLabelValues(label)
 		s.deliveriesRetrying.WithLabelValues(label)
 		s.circuitBreakersOpen.WithLabelValues(label)

internal/metrics/metrics_test.go

@@ -167,6 +167,7 @@ func TestKnownSeriesExistBeforeAnyDelivery(t *testing.T) {
 		"webhooker_deliveries_succeeded_total",
 		"webhooker_deliveries_failed_total",
 		"webhooker_delivery_retries_total",
+		"webhooker_delivery_duration_seconds",
 		"webhooker_circuit_breakers_open",
 	} {
 		assert.ElementsMatch(t,

internal/server/routes_test.go

@@ -1580,3 +1580,31 @@ func TestTwoMetricsRoutersInOneProcess(t *testing.T) {
 		}
 	}
 }
+
+// TestMetricsScrapeBeforeAnyDelivery pins
+// https://git.eeqj.de/sneak/webhooker/issues/267: an instance that
+// has delivered nothing must still serve the delivery duration
+// histogram, at zero, for every target type.
+func TestMetricsScrapeBeforeAnyDelivery(t *testing.T) {
+	t.Parallel()
+
+	env := newTestEnvWithConfig(
+		t, metricsConfig(t, metricsUser, metricsAuthValue),
+	)
+
+	scrape := env.metricsRequest(metricsUser, metricsAuthValue)
+	require.Equal(t, http.StatusOK, scrape.Code)
+
+	for _, targetType := range []database.TargetType{
+		database.TargetTypeHTTP,
+		database.TargetTypeDatabase,
+		database.TargetTypeLog,
+		database.TargetTypeSlack,
+	} {
+		assert.Contains(
+			t, scrape.Body.String(),
+			`webhooker_delivery_duration_seconds_count{target_type="`+
+				string(targetType)+`"} 0`,
+		)
+	}
+}