[hw-7] add metrics, tracing

cart/internal/infra/http/metrics/metrics.go

@@ -0,0 +1,52 @@
+package metrics
+
+import (
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var (
+	requestCounter = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "app",
+		Name:      "requests_total",
+		Help:      "Total amount of request by handler",
+	}, []string{"method", "path", "status_code"})
+
+	requestDurationHistogram = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "app",
+		Name:      "request_duration_seconds",
+		Help:      "Latency of handler processing, seconds",
+		Buckets:   prometheus.DefBuckets,
+	}, []string{"method", "path", "status_code"})
+
+	outboundCounter = promauto.NewCounterVec(prometheus.CounterOpts{
+		Namespace: "app",
+		Name:      "outbound_requests_total",
+		Help:      "Total HTTP requests to external services",
+	}, []string{"method", "url", "status_code"})
+
+	outboundDurationHistogram = promauto.NewHistogramVec(prometheus.HistogramOpts{
+		Namespace: "app",
+		Name:      "outbound_request_duration_seconds",
+		Help:      "Latency of outbound HTTP requests, seconds",
+		Buckets:   prometheus.DefBuckets,
+	}, []string{"method", "url", "status_code"})
+)
+
+func IncRequestHandlerCount(method, path, statusCode string) {
+	requestCounter.WithLabelValues(method, path, statusCode).Inc()
+}
+
+func StoreHandlerRequestDuration(method, path, statusCode string, d time.Duration) {
+	requestDurationHistogram.WithLabelValues(method, path, statusCode).Observe(d.Seconds())
+}
+
+func IncOutboundRequestCount(method, url, status string) {
+	outboundCounter.WithLabelValues(method, url, status).Inc()
+}
+
+func StoreOutboundRequestDuration(method, url, status string, d time.Duration) {
+	outboundDurationHistogram.WithLabelValues(method, url, status).Observe(d.Seconds())
+}

cart/internal/infra/http/metrics/repository.go

@@ -0,0 +1,16 @@
+package metrics
+
+import (
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+var inMemoryObjectsGauge = promauto.NewGauge(prometheus.GaugeOpts{
+	Namespace: "app",
+	Name:      "inmemory_repo_objects",
+	Help:      "Current in-memory repository size",
+})
+
+func SetInMemoryObjects(n int) {
+	inMemoryObjectsGauge.Set(float64(n))
+}