main.go

package main

import (
	"context"
	"errors"
	"os"
	"time"

	"github.com/getsentry/sentry-go"
	"github.com/rs/zerolog"
	"github.com/rs/zerolog/log"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/exporters/jaeger"
	"go.opentelemetry.io/otel/sdk/resource"
	tracesdk "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.12.0"

	"github.com/42atomys/stud42/cmd"
)

func init() {
	log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr}).With().Str("version", os.Getenv("APP_VERSION")).Logger()
	zerolog.TimeFieldFormat = zerolog.TimeFormatUnix
	if os.Getenv("DEBUG") == "true" {
		zerolog.SetGlobalLevel(zerolog.DebugLevel)
	} else {
		zerolog.SetGlobalLevel(zerolog.InfoLevel)
	}
}

func main() {
	ctx := context.Background()

	defer func() {
		err := recover()

		if err != nil {
			sentry.CurrentHub().Recover(err)
			sentry.Flush(time.Second * 5)
		}
	}()

	// Sentry needs to be in main for obscur reason...
	if os.Getenv("GO_ENV") != "development" || os.Getenv("SENTRY_DSN") != "" {
		initSentry()
	}

	if jaegerEndpoint := os.Getenv("JAEGER_ENDPOINT"); jaegerEndpoint != "" {
		log.Info().Msg("initializing jaeger exporter")
		tp, err := tracerProvider((jaegerEndpoint))
		if err != nil {
			log.Fatal().Err(err).Msg("failed to initialize tracer provider")
		}
		// Cleanly shutdown and flush telemetry when the application exits.
		defer func(ctx context.Context) {
			// Do not make the application hang when it is shutdown.
			ctx, cancel := context.WithTimeout(ctx, time.Second*5)
			defer cancel()
			if err := tp.Shutdown(ctx); err != nil {
				log.Fatal().Err(err).Msg("cannot shutdown trace")
			}
		}(ctx)

		// Register our TracerProvider as the global so any imported
		// instrumentation in the future will default to using it.
		otel.SetTracerProvider(tp)

		var cancel context.CancelFunc
		ctx, cancel = context.WithCancel(context.Background())
		defer cancel()
	}

	cmd.Execute(ctx)
}

/**
 * Initialize sentry client
 * https://docs.sentry.io/platforms/go/
 */
func initSentry() {
	var tracesSampleRate, sampleSampleRate = 0.0, 1.0
	var env = "development"
	var release = "stud42@dev"

	if os.Getenv("GO_ENV") == "production" {
		tracesSampleRate = 0.2
		sampleSampleRate = 1.0

		env = "production"
		release = "stud42@" + os.Getenv("APP_VERSION")

		if os.Getenv("SENTRY_DSN") == "" {
			log.Fatal().Msg("SENTRY_DSN is not set")
		}
	}

	err := sentry.Init(sentry.ClientOptions{
		Dsn:         os.Getenv("SENTRY_DSN"),
		Debug:       os.Getenv("DEBUG") == "true",
		Environment: env,
		Release:     release,
		BeforeSend: func(event *sentry.Event, hint *sentry.EventHint) *sentry.Event {
			for _, frame := range event.Exception {
				log.Warn().Err(errors.New(frame.Value)).Str("eventID", string(event.EventID)).Msg("send exception to sentry")
				event.Tags["eventID"] = string(event.EventID)
			}
			return event
		},
		TracesSampleRate: tracesSampleRate,
		SampleRate:       sampleSampleRate,
		AttachStacktrace: true,
	})
	if err != nil {
		log.Fatal().Err(err).Msg("failed to initialize sentry")
	}
}

// tracerProvider 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 tracerProvider(url string) (*tracesdk.TracerProvider, error) {
	// Create the Jaeger exporter
	exp, err := jaeger.New(jaeger.WithCollectorEndpoint(jaeger.WithEndpoint(url)))
	if err != nil {
		return nil, err
	}

	if os.Getenv("APP_NAME") == "" {
		log.Warn().Msg("APP_NAME is not set")
		os.Setenv("APP_NAME", "unknown")
	}

	traceProvider := tracesdk.NewTracerProvider(
		// Always be sure to batch in production.
		tracesdk.WithBatcher(exp),
		// Record information about this application in a Resource.
		tracesdk.WithResource(resource.NewWithAttributes(
			semconv.SchemaURL,
			semconv.ServiceNameKey.String(os.Getenv("APP_NAME")),
			attribute.String("environment", os.Getenv("GO_ENV")),
		)),
	)
	return traceProvider, nil
}