sdnotify

This example demonstrates typical use of a Notifier when starting a service, indicating readiness, and shutting down the service.

package main

import (
	"errors"
	"log"
	"os"
	"time"

	"github.com/mdlayher/sdnotify"
)

func main() {
	// Create a Notifier which will send notifications when running under
	// systemd unit Type=notify, or will no-op otherwise if the NOTIFY_SOCKET
	// environment variable is not set.
	n, err := sdnotify.New()
	if err != nil && !errors.Is(err, os.ErrNotExist) {
		log.Fatalf("failed to open systemd notifier: %v", err)
	}
	// Clean up the notification socket when all done.
	defer n.Close()

	// Now that the Notifier is created, any further method calls will update
	// systemd with the service's readiness state.
	start := time.Now()
	if err := n.Notify(sdnotify.Statusf("starting, waiting %s for readiness", 5*time.Second)); err != nil {
		log.Fatalf("failed to send startup notification: %v", err)
	}

	// Do service initialization work, ex: go srv.Start() ...

	// Indicate the service is now ready so 'systemctl start' and similar
	// commands can unblock.
	err = n.Notify(
		sdnotify.Statusf("service started successfully in %s", time.Since(start)),
		sdnotify.Ready,
	)
	if err != nil {
		log.Fatalf("failed to send ready notification: %v", err)
	}

	// Wait for a signal or cancelation, ex: <-ctx.Done() ...

	// Finally, indicate the service is shutting down.
	err = n.Notify(
		sdnotify.Statusf("received %s, shutting down", os.Interrupt),
		sdnotify.Stopping,
	)
	if err != nil {
		log.Fatalf("failed to send stopping notification: %v", err)
	}
}

Output: