convert systemd unit to Type=notify and report readiness

internal/daemon/daemon.go

@@ -3,6 +3,7 @@ package daemon
 import (
 	"context"
 	"fmt"
+	systemd "github.com/coreos/go-systemd/daemon"
 	"log/slog"
 	"uncloud/internal/machine"
 )
@@ -27,5 +28,18 @@ func New(dataDir string) (*Daemon, error) {
 
 func (d *Daemon) Run(ctx context.Context) error {
 	slog.Info("Starting machine.")
+
+	// Notify systemd that the daemon is ready when the machine is started.
+	go func() {
+		select {
+		case <-d.machine.Started():
+			_, err := systemd.SdNotify(false, systemd.SdNotifyReady)
+			if err != nil {
+				slog.Error("Failed to notify systemd that the daemon is ready.", "error", err)
+			}
+		case <-ctx.Done():
+		}
+	}()
+
 	return d.machine.Run(ctx)
 }

internal/machine/machine.go

@@ -37,6 +37,8 @@ type Machine struct {
 
 	config Config
 	state  *State
+	// started is closed when the machine is ready to serve requests on the local API server.
+	started chan struct{}
 	// initialised is signalled when the machine is configured as a member of a cluster.
 	initialised chan struct{}
 
@@ -90,6 +92,7 @@ func NewMachine(config *Config) (*Machine, error) {
 	m := &Machine{
 		config:        *config,
 		state:         state,
+		started:       make(chan struct{}),
 		initialised:   make(chan struct{}, 1),
 		cluster:       c,
 		newMachinesCh: c.WatchNewMachines(),
@@ -110,6 +113,11 @@ func newGRPCServer(m pb.MachineServer, c pb.ClusterServer) *grpc.Server {
 	return s
 }
 
+// Started returns a channel that is closed when the machine is ready to serve requests on the local API server.
+func (m *Machine) Started() <-chan struct{} {
+	return m.started
+}
+
 // IsInitialised returns true if the machine has been configured as a member of a cluster,
 // either by initialising a new cluster on it or joining an existing one.
 func (m *Machine) IsInitialised() bool {
@@ -141,6 +149,7 @@ func (m *Machine) Run(ctx context.Context) error {
 			return nil
 		},
 	)
+	close(m.started)
 
 	// Control loop for managing the network controller.
 	errGroup.Go(