dbus-shutdown.go

package main

import (
	"fmt"
	"os"
	"time"

	"github.com/godbus/dbus/v5"
)

func simulateWorkload() {
	// Got signal, sleep a bit then exit
	fmt.Println("Preparing to shutdown")
	for i := 0; i < 20; i = i + 1 {
		fmt.Printf(".")
		time.Sleep(time.Second)
	}
	fmt.Println("")
	fmt.Println("All saved, exiting")
	os.Exit(0)
}

// need to tweak InhibitDelayMaxSec= in /etc/systemd/logind.conf
func inhibit() error {
	conn, err := dbus.SystemBus()
	if err != nil {
		return err
	}
	defer conn.Close()
	var fd int
		
	obj := conn.Object("org.freedesktop.login1", "/org/freedesktop/login1")
	what := "shutdown"
	who := "test-app"
	why := "because"
	mode := "delay"
	call := obj.Call("org.freedesktop.login1.Manager.Inhibit", 0, what, who, why, mode)
	if call.Err != nil {
		return call.Err
	}
	err = call.Store(&fd)

	f := os.NewFile(uintptr(fd), "inhibit fd")
	defer f.Close()

	err = conn.AddMatchSignal(
		dbus.WithMatchInterface("org.freedesktop.login1.Manager"),
		dbus.WithMatchMember("PrepareForShutdown"),
		dbus.WithMatchObjectPath("/org/freedesktop/login1"),
	)
	if err != nil {
		return err
	}

	c := make(chan *dbus.Signal, 1)
	conn.Signal(c)

	for v := range c  {
		r, _ := v.Body[0].(bool)
		if r {
			go simulateWorkload()
		}

	}
	return nil
}

func main() {
	err := inhibit()
	if err != nil {
		fmt.Fprintln(os.Stderr, "Failed to inhibit:", err)
		os.Exit(1)
	}
}