Sentry Go SDK - how to manually propagate traces in arbitrary programs

main.go

// This is an example program that demonstrates how to continue a Sentry trace
// for a hypothetical and arbitrary job runner, not a typical web server.
//
// Try it by running:
//
//      go run main.go new
//      go run main.go 55c41d7f4727204c592c87974aa1eedb-01ae7746826ce117-1
//
// To actually report events to Sentry, set the DSN either by editing the
// appropriate line below or setting the environment variable SENTRY_DSN to
// match the DSN of your Sentry project.
//
// The program will print a trace header that can be used to continue a trace in
// a subsequent execution. Passing any invalid string will simply ignore it and
// start a new trace.
package main

import (
	"context"
	"fmt"
	"log"
	"net/http"
	"os"
	"time"

	"github.com/getsentry/sentry-go"
)

func main() {
	if len(os.Args) < 2 {
		fmt.Fprintf(os.Stderr, `usage:
	Create a new trace:
		%s new

	Continue a trace (use the output from a previous run as argument):
		%[1]s SENTRY-TRACE
	Example:
		%[1]s ae8bf3d6d16a2511be0172f32f0f92e6-92adb330ac553437-1
`, os.Args[0])
		os.Exit(1)
	}
	log.SetPrefix("[Demo  ] ")

	err := sentry.Init(sentry.ClientOptions{
		// Either set your DSN here or set the SENTRY_DSN environment variable.
		Dsn: "",
		// Enable printing of SDK debug messages.
		// Useful when getting started or trying to figure something out.
		Debug: true,
		// Enable tracing.
		TracesSampleRate: 1,
	})
	if err != nil {
		log.Fatalf("sentry.Init: %s", err)
	}
	// Flush buffered events before the program terminates.
	// Set the timeout to the maximum duration the program can afford to wait.
	defer sentry.Flush(2 * time.Second)

	sentryTrace := os.Args[1]
	// At the moment the Go SDK only knows how to continue a trace from a
	// request, so we fake one:
	r := &http.Request{
		Header: http.Header{"Sentry-Trace": {sentryTrace}},
	}
	ctx := context.Background()

	span := sentry.StartSpan(ctx, "job",
		sentry.TransactionName("job"),
		sentry.ContinueFromRequest(r),
	)
	defer span.Finish()

	// pretend we're doing some work
	time.Sleep(500 * time.Millisecond)

	log.Printf("Current job: %q", span.ToSentryTrace())
	log.Printf("To simulate continuing the current trace, run: %s %s", os.Args[0], span.ToSentryTrace())
}

Example trace after running the program twice: