chore: establish local platform baseline

internal/observability/dependencies.go

@@ -0,0 +1,35 @@
+package observability
+
+import (
+	"context"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	dependencyUp = promauto.NewGaugeVec(prometheus.GaugeOpts{
+		Namespace: "voice_platform", Subsystem: "dependency", Name: "up",
+		Help: "Whether the last dependency check succeeded.",
+	}, []string{"service", "dependency"})
+	dependencyCheckDuration = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "voice_platform", Subsystem: "dependency", Name: "check_duration_seconds",
+		Help:    "Dependency check duration.",
+		Buckets: []float64{0.001, 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2},
+	}, []string{"service", "dependency"})
+)
+
+func InstrumentDependencyCheck(serviceName, dependency string, check func(context.Context) error) func(context.Context) error {
+	return func(ctx context.Context) error {
+		startedAt := time.Now()
+		err := check(ctx)
+		dependencyCheckDuration.WithLabelValues(serviceName, dependency).Observe(time.Since(startedAt).Seconds())
+		if err != nil {
+			dependencyUp.WithLabelValues(serviceName, dependency).Set(0)
+			return err
+		}
+		dependencyUp.WithLabelValues(serviceName, dependency).Set(1)
+		return nil
+	}
+}