can create matric in there respective module.

core/module/handler/metrics.go

@@ -0,0 +1,68 @@
+package handler
+
+import (
+	"context"
+	"fmt"
+	"sync"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/metric"
+)
+
+// HandlerMetrics exposes handler-related metric instruments.
+type HandlerMetrics struct {
+	SignatureValidationsTotal metric.Int64Counter
+	SchemaValidationsTotal    metric.Int64Counter
+	RoutingDecisionsTotal     metric.Int64Counter
+}
+
+var (
+	handlerMetricsInstance *HandlerMetrics
+	handlerMetricsOnce     sync.Once
+	handlerMetricsErr      error
+)
+
+// GetHandlerMetrics lazily initializes handler metric instruments and returns a cached reference.
+func GetHandlerMetrics(ctx context.Context) (*HandlerMetrics, error) {
+	handlerMetricsOnce.Do(func() {
+		handlerMetricsInstance, handlerMetricsErr = newHandlerMetrics()
+	})
+	return handlerMetricsInstance, handlerMetricsErr
+}
+
+func newHandlerMetrics() (*HandlerMetrics, error) {
+	meter := otel.GetMeterProvider().Meter(
+		"github.com/beckn-one/beckn-onix/handler",
+		metric.WithInstrumentationVersion("1.0.0"),
+	)
+
+	m := &HandlerMetrics{}
+	var err error
+
+	if m.SignatureValidationsTotal, err = meter.Int64Counter(
+		"beckn_signature_validations_total",
+		metric.WithDescription("Signature validation attempts"),
+		metric.WithUnit("{validation}"),
+	); err != nil {
+		return nil, fmt.Errorf("beckn_signature_validations_total: %w", err)
+	}
+
+	if m.SchemaValidationsTotal, err = meter.Int64Counter(
+		"beckn_schema_validations_total",
+		metric.WithDescription("Schema validation attempts"),
+		metric.WithUnit("{validation}"),
+	); err != nil {
+		return nil, fmt.Errorf("beckn_schema_validations_total: %w", err)
+	}
+
+	if m.RoutingDecisionsTotal, err = meter.Int64Counter(
+		"onix_routing_decisions_total",
+		metric.WithDescription("Routing decisions taken by handler"),
+		metric.WithUnit("{decision}"),
+	); err != nil {
+		return nil, fmt.Errorf("onix_routing_decisions_total: %w", err)
+	}
+
+	return m, nil
+}
+