feat: add resilient container restart controls

internal/appupdate/manager.go

@@ -22,6 +22,16 @@ import (
 
 var ErrCredentialMissing = errors.New("Update-Zugang ist noch nicht eingerichtet")
 
+const (
+	agentUnavailableRetryInterval = 2 * time.Second
+	agentAvailableCheckInterval   = time.Minute
+)
+
+type updateAgent interface {
+	Start(context.Context, updateprotocol.Request) error
+	Status(context.Context) (updateprotocol.Status, error)
+}
+
 type State struct {
 	CurrentVersion       string
 	LatestVersion        string
@@ -46,9 +56,10 @@ type Manager struct {
 	logger      *slog.Logger
 	apiURL      string
 	interval    time.Duration
-	agent       *AgentClient
+	agent       updateAgent
 	httpClient  *http.Client
 	checkMu     sync.Mutex
+	requestMu   sync.Mutex
 	stateMu     sync.RWMutex
 	state       State
 	checkSignal chan struct{}
@@ -87,8 +98,8 @@ func New(database *store.Store, cipher *secure.Cipher, apiURL, agentSocket strin
 }
 
 func (m *Manager) Start(ctx context.Context) {
+	go m.monitorAgent(ctx, agentUnavailableRetryInterval, agentAvailableCheckInterval)
 	go func() {
-		m.refreshAgentStatus(ctx)
 		initial := time.NewTimer(15 * time.Second)
 		defer initial.Stop()
 		var ticker *time.Ticker
@@ -121,7 +132,28 @@ func (m *Manager) backgroundCheck(ctx context.Context) {
 	if err := m.CheckNow(checkCtx); err != nil && !errors.Is(err, ErrCredentialMissing) && !errors.Is(err, context.Canceled) {
 		m.logger.Warn("software update check failed", "error", err)
 	}
-	m.refreshAgentStatus(ctx)
+}
+
+func (m *Manager) monitorAgent(ctx context.Context, unavailableInterval, availableInterval time.Duration) {
+	for {
+		m.refreshAgentStatus(ctx)
+		delay := unavailableInterval
+		if m.State().AgentAvailable {
+			delay = availableInterval
+		}
+		timer := time.NewTimer(delay)
+		select {
+		case <-ctx.Done():
+			if !timer.Stop() {
+				select {
+				case <-timer.C:
+				default:
+				}
+			}
+			return
+		case <-timer.C:
+		}
+	}
 }
 
 func (m *Manager) TriggerCheck() {
@@ -190,6 +222,9 @@ func (m *Manager) CheckNow(ctx context.Context) error {
 }
 
 func (m *Manager) RequestUpdate(ctx context.Context, version string) error {
+	m.requestMu.Lock()
+	defer m.requestMu.Unlock()
+
 	version = strings.TrimSpace(version)
 	state := m.State()
 	if !validReleaseVersion(version) || version != state.LatestVersion {
@@ -198,12 +233,16 @@ func (m *Manager) RequestUpdate(ctx context.Context, version string) error {
 	if comparison, err := compareVersions(state.CurrentVersion, version); err != nil || comparison >= 0 {
 		return errors.New("die ausgewählte Version ist nicht neuer als die laufende Version")
 	}
-	if !state.AgentAvailable {
+	status, err := m.UpdateStatus(ctx)
+	if err != nil {
 		return errors.New("Update-Agent ist nicht erreichbar")
 	}
-	if !state.AgentCompatible {
+	if !agentCompatible(status) {
 		return errors.New("Web-App und Update-Agent müssen zuerst gemeinsam mit Docker Compose aktualisiert werden")
 	}
+	if status.Busy() {
+		return errors.New("ein Software-Update läuft bereits")
+	}
 	settings, err := m.store.GetSoftwareUpdateSettings(ctx)
 	if err != nil {
 		return err