observer/pkg/fiber_tracing/middleware.go

package fiber_tracing

// This was copied from "github.com/psmarcin/fiber-opentelemetry/pkg/fiber-otel"
// and slighltly modified but this piece of code is yet to be fully integrated
// into the package.

import (
	"github.com/gofiber/fiber/v2"
	"go.opentelemetry.io/otel"
	semconv "go.opentelemetry.io/otel/semconv/v1.25.0"
	"go.opentelemetry.io/otel/trace"
)

var Tracer = otel.Tracer("fiber_tracing_middleware")

// Config defines the config for middleware.
type middlewareConfig struct {
	Tracer                trace.Tracer
	TracerStartAttributes []trace.SpanStartOption
}

// ConfigDefault is the default config
var configDefault = middlewareConfig{
	Tracer: Tracer,
	TracerStartAttributes: []trace.SpanStartOption{
		trace.WithNewRoot(),
	},
}

// Helper function to set default values
func configDefaults(config ...middlewareConfig) middlewareConfig {
	// Return default config if nothing provided
	if len(config) < 1 {
		return configDefault
	}

	// Override default config
	cfg := config[0]

	if len(cfg.TracerStartAttributes) == 0 {
		cfg.TracerStartAttributes = configDefault.TracerStartAttributes
	}

	return cfg
}

func new(config ...middlewareConfig) fiber.Handler {
	// Set default config
	cfg := configDefaults(config...)

	// Return new handler
	return func(c *fiber.Ctx) error {
		spanStartAttributes := trace.WithAttributes(
			semconv.HTTPMethod(c.Method()),
			semconv.HTTPTarget(string(c.Request().RequestURI())),
			semconv.HTTPRoute(c.Route().Path),
			semconv.HTTPURL(c.OriginalURL()),
			semconv.HostIP(c.IP()),
			semconv.HTTPUserAgent(string(c.Request().Header.UserAgent())),
			semconv.HTTPRequestContentLength(c.Request().Header.ContentLength()),
			semconv.HTTPScheme(c.Protocol()),
			semconv.NetTransportTCP,
		)
		spanKind := trace.WithSpanKind(trace.SpanKindServer)

		opts := []trace.SpanStartOption{
			spanStartAttributes,
			spanKind,
		}
		opts = append(opts, cfg.TracerStartAttributes...)

		otelCtx, span := Tracer.Start(
			c.UserContext(),
			c.Method()+" "+c.OriginalURL(),
			opts...,
		)

		c.SetUserContext(otelCtx)
		defer span.End()

		err := c.Next()

		statusCode := c.Response().StatusCode()
		attrs := semconv.HTTPResponseStatusCode(statusCode)

		span.SetAttributes(attrs)

		return err
	}
}