make changes as per the doc

pkg/telemetry/telemetry.go

@@ -0,0 +1,110 @@
+package telemetry
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	clientprom "github.com/prometheus/client_golang/prometheus"
+	clientpromhttp "github.com/prometheus/client_golang/prometheus/promhttp"
+	"go.opentelemetry.io/contrib/instrumentation/runtime"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	otelprom "go.opentelemetry.io/otel/exporters/prometheus"
+	"go.opentelemetry.io/otel/sdk/metric"
+	"go.opentelemetry.io/otel/sdk/resource"
+
+	"github.com/beckn-one/beckn-onix/pkg/log"
+)
+
+// Config represents OpenTelemetry related configuration.
+type Config struct {
+	ServiceName    string `yaml:"serviceName"`
+	ServiceVersion string `yaml:"serviceVersion"`
+	EnableMetrics  bool   `yaml:"enableMetrics"`
+	Environment    string `yaml:"environment"`
+}
+
+// Provider holds references to telemetry components that need coordinated shutdown.
+type Provider struct {
+	MeterProvider  *metric.MeterProvider
+	MetricsHandler http.Handler
+	Shutdown       func(context.Context) error
+}
+
+// DefaultConfig returns sensible defaults for telemetry configuration.
+func DefaultConfig() *Config {
+	return &Config{
+		ServiceName:    "beckn-onix",
+		ServiceVersion: "dev",
+		EnableMetrics:  true,
+		Environment:    "development",
+	}
+}
+
+// NewProvider wires OpenTelemetry with a Prometheus exporter and exposes /metrics handler.
+func NewProvider(ctx context.Context, cfg *Config) (*Provider, error) {
+	if cfg == nil {
+		cfg = DefaultConfig()
+	}
+	if cfg.ServiceName == "" {
+		cfg.ServiceName = DefaultConfig().ServiceName
+	}
+	if cfg.ServiceVersion == "" {
+		cfg.ServiceVersion = DefaultConfig().ServiceVersion
+	}
+	if cfg.Environment == "" {
+		cfg.Environment = DefaultConfig().Environment
+	}
+
+	if !cfg.EnableMetrics {
+		log.Info(ctx, "OpenTelemetry metrics disabled")
+		return &Provider{
+			Shutdown: func(context.Context) error { return nil },
+		}, nil
+	}
+
+	res, err := resource.New(
+		ctx,
+		resource.WithAttributes(
+			attribute.String("service.name", cfg.ServiceName),
+			attribute.String("service.version", cfg.ServiceVersion),
+			attribute.String("deployment.environment", cfg.Environment),
+		),
+	)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create telemetry resource: %w", err)
+	}
+
+	registry := clientprom.NewRegistry()
+
+	exporter, err := otelprom.New(
+		otelprom.WithRegisterer(registry),
+		otelprom.WithoutUnits(),
+		otelprom.WithoutScopeInfo(),
+	)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create prometheus exporter: %w", err)
+	}
+
+	meterProvider := metric.NewMeterProvider(
+		metric.WithReader(exporter),
+		metric.WithResource(res),
+	)
+
+	otel.SetMeterProvider(meterProvider)
+	log.Infof(ctx, "OpenTelemetry metrics initialized for service=%s version=%s env=%s",
+		cfg.ServiceName, cfg.ServiceVersion, cfg.Environment)
+
+	if err := runtime.Start(runtime.WithMinimumReadMemStatsInterval(0)); err != nil {
+		log.Warnf(ctx, "Failed to start Go runtime instrumentation: %v", err)
+	}
+
+	return &Provider{
+		MeterProvider:  meterProvider,
+		MetricsHandler: clientpromhttp.HandlerFor(registry, clientpromhttp.HandlerOpts{}),
+		Shutdown: func(ctx context.Context) error {
+			return meterProvider.Shutdown(ctx)
+		},
+	}, nil
+}