Add Stop function to Config

This prevents using it during or after the process teardown. Particulary relevant
to async work like the observers.

windows-agent/internal/config/config.go

@@ -23,6 +23,9 @@ import (
 // Config manages configuration parameters. It is a wrapper around a dictionary
 // that reads and updates the config file.
 type Config struct {
+	ctx    context.Context
+	cancel func()
+
 	// data
 	subscription subscription
 	landscape    landscapeConf
@@ -35,6 +38,7 @@ type Config struct {
 
 	// observers are called after any configuration changes.
 	observers []func()
+	wg        sync.WaitGroup
 }
 
 // New creates and initializes a new Config object.
@@ -44,20 +48,59 @@ func New(ctx context.Context, cachePath string) (m *Config) {
 		mu:        &sync.Mutex{},
 	}
 
+	m.ctx, m.cancel = context.WithCancel(ctx)
+
 	return m
 }
 
+// Stop releases all resources associated with the config.
+func (c *Config) Stop() {
+	c.cancel()
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.wg.Wait()
+}
+
+func (c *Config) stopped() bool {
+	select {
+	case <-c.ctx.Done():
+		return true
+	default:
+		return false
+	}
+}
+
 // Notify appends a callback. It'll be called every time any configuration changes.
 func (c *Config) Notify(f func()) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
 	c.observers = append(c.observers, f)
 }
 
+// notifyObservers calls all the observers. Use it under a mutex.
 func (c *Config) notifyObservers() {
+	c.wg.Add(len(c.observers))
+
 	for _, f := range c.observers {
-		// This needs to be in a goroutine because notifyObservers is sometimes
+		f := f
+		// This needs to be in a goroutine because notifyObservers is always
 		// called under the config mutex. The callback trying to grab the mutex
 		// (to read the config) would cause a deadlock otherwise.
-		go f()
+		//
+		// We protect it under "stopped" to avoid running callbacks during the
+		// agent's shutdown.
+		go func() {
+			defer c.wg.Done()
+
+			if c.stopped() {
+				return
+			}
+
+			f()
+		}()
 	}
 }
 
@@ -66,6 +109,10 @@ func (c *Config) Subscription(ctx context.Context) (token string, source Source,
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
+	if c.stopped() {
+		return "", SourceNone, errors.New("config stopped")
+	}
+
 	if err := c.load(); err != nil {
 		return "", SourceNone, fmt.Errorf("could not load: %v", err)
 	}
@@ -82,6 +129,10 @@ func (c *Config) ProvisioningTasks(ctx context.Context, distroName string) ([]ta
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
+	if c.stopped() {
+		return nil, errors.New("config stopped")
+	}
+
 	if err := c.load(); err != nil {
 		return nil, fmt.Errorf("could not load: %v", err)
 	}
@@ -103,6 +154,10 @@ func (c *Config) LandscapeClientConfig(ctx context.Context) (string, Source, err
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
+	if c.stopped() {
+		return "", SourceNone, errors.New("config stopped")
+	}
+
 	if err := c.load(); err != nil {
 		return "", SourceNone, fmt.Errorf("could not load: %v", err)
 	}
@@ -139,6 +194,10 @@ func (c *Config) set(ctx context.Context, field *string, value string) error {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
+	if c.stopped() {
+		return errors.New("config stopped")
+	}
+
 	// Load before dumping to avoid overriding recent changes to file
 	if err := c.load(); err != nil {
 		return err
@@ -164,6 +223,10 @@ func (c *Config) LandscapeAgentUID(ctx context.Context) (string, error) {
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
+	if c.stopped() {
+		return "", errors.New("config stopped")
+	}
+
 	if err := c.load(); err != nil {
 		return "", fmt.Errorf("could not load: %v", err)
 	}
@@ -246,6 +309,10 @@ func (c *Config) collectRegistrySettingsTasks(ctx context.Context, data Registry
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
+	if c.stopped() {
+		return nil, errors.New("config stopped")
+	}
+
 	// Load up-to-date state
 	if err := c.load(); err != nil {
 		return nil, err

windows-agent/internal/config/config_marshal.go

@@ -44,7 +44,7 @@ func (c *Config) load() (err error) {
 	return nil
 }
 
-func (c Config) dump() (err error) {
+func (c *Config) dump() (err error) {
 	defer decorate.OnError(&err, "could not store Config data")
 
 	h := marshalHelper{

windows-agent/internal/config/config_test.go

@@ -90,6 +90,7 @@ func TestSubscription(t *testing.T) {
 
 			setup, dir := setUpMockSettings(t, ctx, db, tc.settingsState, tc.breakFile)
 			conf := config.New(ctx, dir)
+			defer conf.Stop()
 			setup(t, conf)
 
 			token, source, err := conf.Subscription(ctx)
@@ -146,6 +147,7 @@ func TestLandscapeConfig(t *testing.T) {
 
 			setup, dir := setUpMockSettings(t, ctx, db, tc.settingsState, tc.breakFile)
 			conf := config.New(ctx, dir)
+			defer conf.Stop()
 			setup(t, conf)
 
 			landscapeConf, source, err := conf.LandscapeClientConfig(ctx)
@@ -201,6 +203,7 @@ func TestLandscapeAgentUID(t *testing.T) {
 			}
 
 			conf := config.New(ctx, dir)
+			defer conf.Stop()
 			setup(t, conf)
 
 			v, err := conf.LandscapeAgentUID(ctx)
@@ -313,6 +316,7 @@ func TestSetUserSubscription(t *testing.T) {
 
 			setup, dir := setUpMockSettings(t, ctx, db, tc.settingsState, tc.breakFile)
 			conf := config.New(ctx, dir)
+			defer conf.Stop()
 			setup(t, conf)
 
 			token := "new_token"
@@ -370,6 +374,7 @@ func TestSetLandscapeAgentUID(t *testing.T) {
 
 			setup, dir := setUpMockSettings(t, ctx, db, tc.settingsState, tc.breakFile)
 			conf := config.New(ctx, dir)
+			defer conf.Stop()
 			setup(t, conf)
 
 			uid := "new_uid"
@@ -443,6 +448,7 @@ func TestFetchMicrosoftStoreSubscription(t *testing.T) {
 
 			setup, dir := setUpMockSettings(t, ctx, db, tc.settingsState, tc.breakConfigFile)
 			c := config.New(ctx, dir)
+			defer c.Stop()
 			setup(t, c)
 
 			// Set up the mock Microsoft store
@@ -548,6 +554,7 @@ func TestUpdateRegistryData(t *testing.T) {
 
 			_, dir := setUpMockSettings(t, ctx, db, tc.settingsState, tc.breakConfigFile)
 			c := config.New(ctx, dir)
+			defer c.Stop()
 
 			// Enter a first set of data to override the defaults
 			err = c.UpdateRegistryData(ctx, config.RegistryData{
@@ -651,6 +658,7 @@ func TestNotify(t *testing.T) {
 
 	_, dir := setUpMockSettings(t, ctx, db, untouched, false)
 	c := config.New(ctx, dir)
+	defer c.Stop()
 
 	var notifyCount atomic.Int32
 	var wantNotifyCount int32

windows-agent/internal/proservices/proservices.go

@@ -24,6 +24,7 @@ type Manager struct {
 	landscapeService   *landscape.Service
 	registryWatcher    *registrywatcher.Service
 	db                 *database.DistroDB
+	conf               *config.Config
 }
 
 // options are the configurable functional options for the daemon.
@@ -67,25 +68,25 @@ func New(ctx context.Context, publicDir, privateDir string, args ...Option) (s M
 	//[GitHub](https://github.com/canonical/ubuntu-pro-for-wsl/pull/438)
 	InitWSLAPI()
 
-	conf := config.New(ctx, privateDir)
+	s.conf = config.New(ctx, privateDir)
 
-	db, err := database.New(ctx, privateDir, conf)
+	db, err := database.New(ctx, privateDir, s.conf)
 	if err != nil {
 		return s, err
 	}
 	s.db = db
 
-	w := registrywatcher.New(ctx, conf, s.db, registrywatcher.WithRegistry(opts.registry))
+	w := registrywatcher.New(ctx, s.conf, s.db, registrywatcher.WithRegistry(opts.registry))
 	s.registryWatcher = &w
 	s.registryWatcher.Start()
 
-	if err := conf.FetchMicrosoftStoreSubscription(ctx); err != nil {
+	if err := s.conf.FetchMicrosoftStoreSubscription(ctx); err != nil {
 		log.Warningf(ctx, "%v", err)
 	}
 
-	s.uiService = ui.New(ctx, conf, s.db)
+	s.uiService = ui.New(ctx, s.conf, s.db)
 
-	landscape, err := landscape.New(ctx, conf, s.db)
+	landscape, err := landscape.New(ctx, s.conf, s.db)
 	if err != nil {
 		return s, err
 	}
@@ -117,6 +118,10 @@ func (m Manager) Stop(ctx context.Context) {
 	if m.db != nil {
 		m.db.Close(ctx)
 	}
+
+	if m.conf != nil {
+		m.conf.Stop()
+	}
 }
 
 // RegisterGRPCServices returns a new grpc Server with the 2 api services attached to it.

windows-agent/internal/proservices/ui/ui_test.go

@@ -30,6 +30,7 @@ func TestNew(t *testing.T) {
 	defer db.Close(ctx)
 
 	conf := config.New(ctx, dir)
+	defer conf.Stop()
 
 	_ = ui.New(context.Background(), conf, db)
 }
@@ -92,6 +93,8 @@ func TestAttachPro(t *testing.T) {
 			}
 
 			conf := config.New(ctx, dir)
+			defer conf.Stop()
+
 			if tc.higherPriorityToken {
 				err = conf.UpdateRegistryData(ctx, config.RegistryData{
 					UbuntuProToken: "organization_token",