[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))
+}

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

@@ -0,0 +1,38 @@
+package middlewares
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"route256/cart/internal/infra/http/metrics"
+)
+
+type statusWriter struct {
+	http.ResponseWriter
+	statusCode int
+}
+
+func (w *statusWriter) WriteHeader(code int) {
+	w.statusCode = code
+	w.ResponseWriter.WriteHeader(code)
+}
+
+func NewMetricsMiddleware(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		sw := &statusWriter{
+			ResponseWriter: w,
+			statusCode:     http.StatusOK,
+		}
+
+		start := time.Now()
+
+		h.ServeHTTP(sw, r)
+
+		path := r.URL.Path
+		status := strconv.Itoa(sw.statusCode)
+
+		metrics.IncRequestHandlerCount(r.Method, path, status)
+		metrics.StoreHandlerRequestDuration(r.Method, path, status, time.Since(start))
+	})
+}

cart/internal/infra/http/middlewares/tracing.go

@@ -0,0 +1,17 @@
+package middlewares
+
+import (
+	"net/http"
+
+	"route256/cart/internal/infra/tracing"
+)
+
+func NewTracingMiddleware(h http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		ctx, span := tracing.Tracer().Start(r.Context(),
+			r.Method+" "+r.URL.Path)
+		defer span.End()
+
+		h.ServeHTTP(w, r.WithContext(ctx))
+	})
+}

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

@@ -0,0 +1,37 @@
+package round_trippers
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"route256/cart/internal/infra/http/metrics"
+)
+
+type MetricsRoundTripper struct {
+	rt http.RoundTripper
+}
+
+func NewMetricsRoundTripper(rt http.RoundTripper) http.RoundTripper {
+	return &MetricsRoundTripper{
+		rt: rt,
+	}
+}
+
+func (m *MetricsRoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
+	start := time.Now()
+	resp, err := m.rt.RoundTrip(r)
+
+	status := "error"
+
+	if resp != nil {
+		status = strconv.Itoa(resp.StatusCode)
+	}
+
+	url := r.URL.Path
+
+	metrics.IncOutboundRequestCount(r.Method, url, status)
+	metrics.StoreOutboundRequestDuration(r.Method, url, status, time.Since(start))
+
+	return resp, err
+}