tracing.go

package main

import (
	"net/http"

	"go-micro.dev/v4/metadata"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/exporters/jaeger"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/sdk/resource"
	tracesdk "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.12.0"
)

// newTracerProvider returns an OpenTelemetry TracerProvider configured to use
// the Jaeger exporter that will send spans to the provided url. The returned
// TracerProvider will also use a Resource configured with all the information
// about the application.
func newTracerProvider(serviceName, serviceID, url string) (*tracesdk.TracerProvider, error) {
	// Create the Jaeger exporter
	exp, err := jaeger.New(jaeger.WithCollectorEndpoint(jaeger.WithEndpoint(url)))
	if err != nil {
		return nil, err
	}
	tp := tracesdk.NewTracerProvider(
		tracesdk.WithBatcher(exp),
		tracesdk.WithResource(resource.NewWithAttributes(
			semconv.SchemaURL,
			semconv.ServiceNameKey.String(serviceName),
			semconv.ServiceVersionKey.String(version),
			semconv.ServiceInstanceIDKey.String(serviceID),
		)),
		tracesdk.WithSampler(tracesdk.AlwaysSample()),
	)
	otel.SetTracerProvider(tp)
	otel.SetTextMapPropagator(propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{}))
	return tp, nil
}

func tracingContextWrapper(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		propagator, md := otel.GetTextMapPropagator(), make(metadata.Metadata)
		propagator.Inject(r.Context(), propagation.MapCarrier(md))
		r2 := r.WithContext(metadata.NewContext(r.Context(), md))
		next.ServeHTTP(w, r2)
	})
}