[#451] frostfs-node: Add cache metrics

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

internal/metrics/cache.go

@@ -0,0 +1,35 @@
+package metrics
+
+import (
+	"strconv"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/metrics"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+var cacheRequests = metrics.NewHistogramVec(prometheus.HistogramOpts{
+	Namespace: namespace,
+	Subsystem: commonCacheSubsystem,
+	Name:      "request_duration_seconds",
+	Help:      "Accumulated common cache request process duration",
+}, []string{hitLabel, methodLabel, cacheLabel})
+
+type CacheMetrics struct {
+	cache string
+}
+
+// NewCacheMetrics returns new CacheMetrics instance for cache specified.
+func NewCacheMetrics(cache string) *CacheMetrics {
+	return &CacheMetrics{
+		cache: cache,
+	}
+}
+
+func (m *CacheMetrics) AddMethodDuration(method string, d time.Duration, hit bool) {
+	cacheRequests.With(prometheus.Labels{
+		hitLabel:    strconv.FormatBool(hit),
+		methodLabel: method,
+		cacheLabel:  m.cache,
+	}).Observe(d.Seconds())
+}