feat(BRIDGE-278): Rollout Feature Flag stickiness support; a new UUID 'sticky' value has been added to the vault"

go.mod

@@ -9,7 +9,7 @@ require (
 	github.com/Masterminds/semver/v3 v3.2.0
 	github.com/ProtonMail/gluon v0.17.1-0.20250627102828-b014b7cc8132
 	github.com/ProtonMail/go-autostart v0.0.0-20210130080809-00ed301c8e9a
-	github.com/ProtonMail/go-proton-api v0.4.1-0.20250627100628-e6d3af81dfdf
+	github.com/ProtonMail/go-proton-api v0.4.1-0.20250627135952-bf973947255c
 	github.com/ProtonMail/gopenpgp/v2 v2.9.0-proton
 	github.com/PuerkitoBio/goquery v1.8.1
 	github.com/abiosoft/ishell v2.0.0+incompatible

go.sum

@@ -45,8 +45,8 @@ github.com/ProtonMail/go-message v0.13.1-0.20240919135104-3bc88e6a9423 h1:p8nBDx
 github.com/ProtonMail/go-message v0.13.1-0.20240919135104-3bc88e6a9423/go.mod h1:NBAn21zgCJ/52WLDyed18YvYFm5tEoeDauubFqLokM4=
 github.com/ProtonMail/go-mime v0.0.0-20230322103455-7d82a3887f2f h1:tCbYj7/299ekTTXpdwKYF8eBlsYsDVoggDAuAjoK66k=
 github.com/ProtonMail/go-mime v0.0.0-20230322103455-7d82a3887f2f/go.mod h1:gcr0kNtGBqin9zDW9GOHcVntrwnjrK+qdJ06mWYBybw=
-github.com/ProtonMail/go-proton-api v0.4.1-0.20250627100628-e6d3af81dfdf h1:lGyK9G1hyAzUBhkU1wmc6oYPnUTwrRBnVb6YA14Z/bk=
+github.com/ProtonMail/go-proton-api v0.4.1-0.20250627135952-bf973947255c h1:FhfHIrGgehnTV/T2NkyVauKcJ3NzPq1uLcU/0eK661A=
-github.com/ProtonMail/go-proton-api v0.4.1-0.20250627100628-e6d3af81dfdf/go.mod h1:9t9+oQfH+6ssa7O2nLv34Uyjv8UmqTPGbVNcFToewck=
+github.com/ProtonMail/go-proton-api v0.4.1-0.20250627135952-bf973947255c/go.mod h1:9t9+oQfH+6ssa7O2nLv34Uyjv8UmqTPGbVNcFToewck=
 github.com/ProtonMail/go-smtp v0.0.0-20231109081432-2b3d50599865 h1:EP1gnxLL5Z7xBSymE9nSTM27nRYINuvssAtDmG0suD8=
 github.com/ProtonMail/go-smtp v0.0.0-20231109081432-2b3d50599865/go.mod h1:qm27SGYgoIPRot6ubfQ/GpiPy/g3PaZAVRxiO/sDUgQ=
 github.com/ProtonMail/go-srp v0.0.7 h1:Sos3Qk+th4tQR64vsxGIxYpN3rdnG9Wf9K4ZloC1JrI=

internal/bridge/bridge.go

@@ -57,6 +57,7 @@ import (
 	"github.com/bradenaw/juniper/xslices"
 	"github.com/elastic/go-sysinfo/types"
 	"github.com/go-resty/resty/v2"
+	uuid "github.com/google/uuid"
 	"github.com/sirupsen/logrus"
 )
 
@@ -271,7 +272,7 @@ func newBridge(
 		return nil, fmt.Errorf("failed to create focus service: %w", err)
 	}
 
-	unleashService := unleash.NewBridgeService(ctx, api, locator, panicHandler)
+	unleashService := unleash.NewBridgeService(ctx, api, locator, panicHandler, vault.GetFeatureFlagStickyKey())
 
 	observabilityService := observability.NewService(ctx, panicHandler)
 
@@ -785,3 +786,7 @@ func (bridge *Bridge) SetHostVersionGetterTest(fn func(host types.Host) string)
 func (bridge *Bridge) SetRolloutPercentageTest(rollout float64) error {
 	return bridge.vault.SetUpdateRollout(rollout)
 }
+
+func (bridge *Bridge) GetFeatureFlagStickyKey() uuid.UUID {
+	return bridge.vault.GetFeatureFlagStickyKey()
+}

internal/bridge/bridge_test.go

@@ -56,6 +56,7 @@ import (
 	imapid "github.com/emersion/go-imap-id"
 	"github.com/emersion/go-sasl"
 	"github.com/emersion/go-smtp"
+	"github.com/google/uuid"
 	"github.com/stretchr/testify/require"
 	"go.uber.org/goleak"
 )
@@ -778,6 +779,30 @@ func TestBridge_ChangeCacheDirectory(t *testing.T) {
 	})
 }
 
+func TestBridge_FeatureFlagStickyKey_Persistence(t *testing.T) {
+	var uuidOne uuid.UUID
+	var uuidTwo uuid.UUID
+
+	withEnv(t, func(ctx context.Context, s *server.Server, netCtl *proton.NetCtl, locator bridge.Locator, vaultKey []byte) {
+		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, vaultKey, func(b *bridge.Bridge, _ *bridge.Mocks) {
+			uuidOne = b.GetFeatureFlagStickyKey()
+		})
+		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, vaultKey, func(b *bridge.Bridge, _ *bridge.Mocks) {
+			require.Equal(t, uuidOne, b.GetFeatureFlagStickyKey())
+		})
+	})
+
+	withEnv(t, func(ctx context.Context, s *server.Server, netCtl *proton.NetCtl, locator bridge.Locator, vaultKey []byte) {
+		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, vaultKey, func(b *bridge.Bridge, _ *bridge.Mocks) {
+			uuidTwo = b.GetFeatureFlagStickyKey()
+			require.NotEqual(t, uuidOne, uuidTwo)
+		})
+		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, vaultKey, func(b *bridge.Bridge, _ *bridge.Mocks) {
+			require.Equal(t, uuidTwo, b.GetFeatureFlagStickyKey())
+		})
+	})
+}
+
 func TestBridge_ChangeAddressOrder(t *testing.T) {
 	withEnv(t, func(ctx context.Context, s *server.Server, netCtl *proton.NetCtl, locator bridge.Locator, vaultKey []byte) {
 		// Create a user.

internal/unleash/service.go

@@ -28,6 +28,7 @@ import (
 	"github.com/ProtonMail/gluon/async"
 	"github.com/ProtonMail/go-proton-api"
 	"github.com/ProtonMail/proton-bridge/v3/internal/service"
+	"github.com/google/uuid"
 	"github.com/sirupsen/logrus"
 )
 
@@ -83,7 +84,13 @@ type Service struct {
 	getFeaturesFn func(ctx context.Context) (proton.FeatureFlagResult, error)
 }
 
-func NewBridgeService(ctx context.Context, api *proton.Manager, locator service.Locator, panicHandler async.PanicHandler) *Service {
+func NewBridgeService(
+	ctx context.Context,
+	api *proton.Manager,
+	locator service.Locator,
+	panicHandler async.PanicHandler,
+	featureFlagUUID uuid.UUID,
+) *Service {
 	log := logrus.WithField("service", "unleash")
 	cacheDir, err := locator.ProvideUnleashCachePath()
 	if err != nil {
@@ -92,7 +99,7 @@ func NewBridgeService(ctx context.Context, api *proton.Manager, locator service.
 	cachePath := filepath.Clean(filepath.Join(cacheDir, filename))
 
 	return newService(ctx, func(ctx context.Context) (proton.FeatureFlagResult, error) {
-		return api.GetFeatures(ctx)
+		return api.GetFeatures(ctx, featureFlagUUID)
 	}, log, cachePath, panicHandler)
 }
 

internal/vault/types_data.go

@@ -17,17 +17,22 @@
 
 package vault
 
+import "github.com/google/uuid"
+
 type Data struct {
 	Settings Settings
 	Users    []UserData
 	Cookies  []byte
 	Certs    Certs
 	Migrated bool
+	// FeatureFlagStickyKey a utility value for ensuring rollout feature flags "stick" to a particular Bridge client.
+	FeatureFlagStickyKey uuid.UUID
 }
 
 func newDefaultData(gluonDir string) Data {
 	return Data{
-		Settings: newDefaultSettings(gluonDir),
+		Settings:             newDefaultSettings(gluonDir),
-		Certs:    newDefaultCerts(),
+		Certs:                newDefaultCerts(),
+		FeatureFlagStickyKey: uuid.New(),
 	}
 }

internal/vault/vault.go

@@ -32,6 +32,7 @@ import (
 	"github.com/ProtonMail/gluon/async"
 	"github.com/bradenaw/juniper/parallel"
 	"github.com/bradenaw/juniper/xslices"
+	"github.com/google/uuid"
 	"github.com/sirupsen/logrus"
 )
 
@@ -76,6 +77,10 @@ func New(vaultDir, gluonCacheDir string, key []byte, panicHandler async.PanicHan
 		return nil, corrupt, err
 	}
 
+	if err := vault.setFeatureFlagStickyKeyIfEmpty(); err != nil {
+		return vault, corrupt, err
+	}
+
 	vault.panicHandler = panicHandler
 
 	return vault, corrupt, nil
@@ -91,6 +96,22 @@ func (vault *Vault) GetUserIDs() []string {
 	})
 }
 
+// GetFeatureFlagStickyKey - the sticky key is  a utility value for ensuring rollout feature flags "stick" to a particular Bridge client.
+func (vault *Vault) GetFeatureFlagStickyKey() uuid.UUID {
+	return vault.getSafe().FeatureFlagStickyKey
+}
+
+// setFeatureFlagStickyKeyIfEmpty - checks if the sticky key is nil in the vault and if so generates a new one.
+func (vault *Vault) setFeatureFlagStickyKeyIfEmpty() error {
+	if vault.getSafe().FeatureFlagStickyKey != uuid.Nil {
+		return nil
+	}
+
+	return vault.modSafe(func(data *Data) {
+		data.FeatureFlagStickyKey = uuid.New()
+	})
+}
+
 func (vault *Vault) getUsers() ([]*User, error) {
 	vault.lock.Lock()
 	defer vault.lock.Unlock()