observer/pkg/fiber_tracing/fiber_tracing.go

package fiber_tracing

import (
	"context"
	"log"

	"git.ma-al.com/maal-libraries/observer/pkg/exporters"
	"github.com/gofiber/fiber/v2"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/sdk/resource"
	trc "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.25.0"
	trace "go.opentelemetry.io/otel/trace"
)

var (
	TracingError error = nil
	TP           trc.TracerProvider
)

type Config struct {
	AppName string
	Version string
	// Name of an organization providing the service
	ServiceProvider string
	Exporters       []exporters.TraceExporter
}

func newResource(config Config) *resource.Resource {
	r := resource.NewWithAttributes(
		semconv.SchemaURL,
		semconv.ServiceNameKey.String(config.AppName),
		semconv.ServiceVersionKey.String(config.Version),
		attribute.String("service.provider", config.ServiceProvider),
	)
	return r
}

// NOTE: You can use [trace.WithAttributes] as a parameter to opts argument
func Start(ctx context.Context, spanName string, opts ...trace.SpanStartOption) (context.Context, trace.Span) {
	return Tracer.Start(ctx, spanName, opts...)
}

// NOTE: You can use [trace.WithAttributes] as a parameter to opts argument
// Returns [c.UserContext] as [context.Context]
func FStart(c *fiber.Ctx, opts ...trace.SpanStartOption) (context.Context, trace.Span) {
	return Tracer.Start(c.UserContext(), c.Method()+" "+c.Route().Path, opts...)
}

// Just like [FStart] but makes it possible to assign custom span name.
func FStartRenamed(c *fiber.Ctx, spanName string, opts ...trace.SpanStartOption) (context.Context, trace.Span) {
	return Tracer.Start(c.UserContext(), spanName, opts...)
}

// Retrieve span using [fiber.Ctx]
func SpanFromContext(c *fiber.Ctx) trace.Span {
	return trace.SpanFromContext(c.UserContext())
}

func NewMiddleware(config Config) func(*fiber.Ctx) error {
	var tracerProviders []trc.TracerProviderOption

	for _, exp := range config.Exporters {
		tracerProviders = append(tracerProviders, exp.IntoTraceProviderOption())
	}
	tracerProviders = append(tracerProviders, trc.WithResource(newResource(config)))

	TP = *trc.NewTracerProvider(tracerProviders...)

	otel.SetTracerProvider(&TP)
	otel.SetErrorHandler(otel.ErrorHandlerFunc(func(err error) {
		if err != TracingError {
			TracingError = err
			log.Println(err)
		}
	}))

	tracer := TP.Tracer("_maal-fiber-otel_")

	return new(
		middlewareConfig{
			Tracer: tracer,
			TracerStartAttributes: []trace.SpanStartOption{
				trace.WithSpanKind(trace.SpanKindServer),
				trace.WithNewRoot(),
			},
		},
	)
}

func ShutdownTracer() {
	if err := TP.Shutdown(context.Background()); err != nil {
		log.Fatal(err)
	}
}