Add obsx library

tracer.go

@@ -0,0 +1,67 @@
+package obsx
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/sdk/resource"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.26.0"
+	"go.opentelemetry.io/otel/trace"
+)
+
+// TracerConfig configures the OpenTelemetry tracer.
+type TracerConfig struct {
+	ServiceName    string
+	ServiceVersion string
+	Endpoint       string  // OTLP gRPC endpoint, e.g. "localhost:4317"
+	Sampler        float64 // sampling ratio, default: 1.0 (sample everything)
+}
+
+func (c *TracerConfig) defaults() {
+	if c.Sampler <= 0 {
+		c.Sampler = 1.0
+	}
+}
+
+// SetupTracer initializes an OpenTelemetry tracer provider with OTLP gRPC exporter.
+// Returns a shutdown function that must be called on application exit.
+func SetupTracer(ctx context.Context, cfg TracerConfig) (shutdown func(context.Context) error, err error) {
+	cfg.defaults()
+
+	exporter, err := otlptracegrpc.New(ctx,
+		otlptracegrpc.WithEndpoint(cfg.Endpoint),
+		otlptracegrpc.WithInsecure(),
+	)
+	if err != nil {
+		return nil, err
+	}
+
+	attrs := []resource.Option{
+		resource.WithAttributes(semconv.ServiceName(cfg.ServiceName)),
+	}
+	if cfg.ServiceVersion != "" {
+		attrs = append(attrs, resource.WithAttributes(semconv.ServiceVersion(cfg.ServiceVersion)))
+	}
+
+	res, err := resource.New(ctx, attrs...)
+	if err != nil {
+		return nil, err
+	}
+
+	tp := sdktrace.NewTracerProvider(
+		sdktrace.WithBatcher(exporter),
+		sdktrace.WithResource(res),
+		sdktrace.WithSampler(sdktrace.TraceIDRatioBased(cfg.Sampler)),
+	)
+
+	otel.SetTracerProvider(tp)
+
+	return tp.Shutdown, nil
+}
+
+// StartSpan starts a new span using the global tracer provider.
+func StartSpan(ctx context.Context, name string, opts ...trace.SpanStartOption) (context.Context, trace.Span) {
+	return otel.Tracer("obsx").Start(ctx, name, opts...)
+}