Add otel tracer

Signed-off-by: Asai Neko <sugar@sne.moe>

tracer/otel_tracer.go

@@ -0,0 +1,58 @@
+package tracer
+
+import (
+	"context"
+	"log/slog"
+	"time"
+
+	"github.com/spf13/viper"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/propagation"
+	"go.opentelemetry.io/otel/sdk/resource"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.24.0"
+)
+
+func Init(ctx context.Context) func(context.Context) error {
+	endpoint := viper.GetString("tracer.otel_controller_endpoint")
+	if endpoint == "" {
+		endpoint = "localhost:4317"
+	}
+
+	clientCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
+	defer cancel()
+
+	exporter, err := otlptracegrpc.New(clientCtx,
+		otlptracegrpc.WithEndpoint(endpoint),
+		otlptracegrpc.WithInsecure(),
+	)
+	if err != nil {
+		slog.Error("[Tracer] Failed to create trace exporter", "err", err)
+		return func(context.Context) error { return nil }
+	}
+
+	res, err := resource.New(ctx,
+		resource.WithAttributes(
+			semconv.ServiceNameKey.String("nixcn-cms-backend"),
+		),
+	)
+	if err != nil {
+		slog.Error("[Tracer] Failed to create resource", "err", err)
+	}
+
+	tp := sdktrace.NewTracerProvider(
+		sdktrace.WithBatcher(exporter),
+		sdktrace.WithResource(res),
+		sdktrace.WithSampler(sdktrace.AlwaysSample()),
+	)
+
+	otel.SetTracerProvider(tp)
+
+	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(
+		propagation.TraceContext{},
+		propagation.Baggage{},
+	))
+
+	return tp.Shutdown
+}