[#451] metrics: Move to internal

`metrics` don't look like something others want to import.

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

internal/metrics/object.go

@@ -0,0 +1,49 @@
+package metrics
+
+import (
+	"strconv"
+	"time"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-observability/metrics"
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+type ObjectServiceMetrics interface {
+	AddRequestDuration(method string, d time.Duration, success bool)
+	AddPayloadSize(method string, size int)
+}
+
+type objectServiceMetrics struct {
+	methodDuration *prometheus.HistogramVec
+	payloadCounter *prometheus.CounterVec
+}
+
+func newObjectServiceMetrics() *objectServiceMetrics {
+	return &objectServiceMetrics{
+		methodDuration: metrics.NewHistogramVec(prometheus.HistogramOpts{
+			Namespace: namespace,
+			Subsystem: objectSubsystem,
+			Name:      "request_duration_seconds",
+			Help:      "Object Service request process duration",
+		}, []string{methodLabel, successLabel}),
+		payloadCounter: metrics.NewCounterVec(prometheus.CounterOpts{
+			Namespace: namespace,
+			Subsystem: objectSubsystem,
+			Name:      "request_payload_bytes",
+			Help:      "Object Service request payload",
+		}, []string{methodLabel}),
+	}
+}
+
+func (m *objectServiceMetrics) AddRequestDuration(method string, d time.Duration, success bool) {
+	m.methodDuration.With(prometheus.Labels{
+		methodLabel:  method,
+		successLabel: strconv.FormatBool(success),
+	}).Observe(d.Seconds())
+}
+
+func (m *objectServiceMetrics) AddPayloadSize(method string, size int) {
+	m.payloadCounter.With(prometheus.Labels{
+		methodLabel: method,
+	}).Add(float64(size))
+}