feat(BRIDGE-119): added support for Feature Flags

internal/bridge/bridge.go

@@ -47,6 +47,7 @@ import (
 	"github.com/ProtonMail/proton-bridge/v3/internal/services/imapsmtpserver"
 	"github.com/ProtonMail/proton-bridge/v3/internal/services/syncservice"
 	"github.com/ProtonMail/proton-bridge/v3/internal/telemetry"
+	"github.com/ProtonMail/proton-bridge/v3/internal/unleash"
 	"github.com/ProtonMail/proton-bridge/v3/internal/user"
 	"github.com/ProtonMail/proton-bridge/v3/internal/vault"
 	"github.com/ProtonMail/proton-bridge/v3/pkg/keychain"
@@ -136,6 +137,8 @@ type Bridge struct {
 
 	serverManager *imapsmtpserver.Service
 	syncService   *syncservice.Service
+	// unleashService is responsible for polling the feature flags and caching
+	unleashService *unleash.Service
 }
 
 var logPkg = logrus.WithField("pkg", "bridge") //nolint:gochecknoglobals
@@ -253,6 +256,8 @@ func newBridge(
 		return nil, fmt.Errorf("failed to create focus service: %w", err)
 	}
 
+	unleashService := unleash.NewBridgeService(ctx, api, locator, panicHandler)
+
 	bridge := &Bridge{
 		vault: vault,
 
@@ -293,6 +298,8 @@ func newBridge(
 
 		tasks:       tasks,
 		syncService: syncservice.NewService(reporter, panicHandler),
+
+		unleashService: unleashService,
 	}
 
 	bridge.serverManager = imapsmtpserver.NewService(context.Background(),
@@ -320,6 +327,8 @@ func newBridge(
 
 	bridge.syncService.Run()
 
+	bridge.unleashService.Run()
+
 	return bridge, nil
 }
 
@@ -470,6 +479,9 @@ func (bridge *Bridge) Close(ctx context.Context) {
 	// Close the focus service.
 	bridge.focusService.Close()
 
+	// Close the unleash service.
+	bridge.unleashService.Close()
+
 	// Close the watchers.
 	bridge.watchersLock.Lock()
 	defer bridge.watchersLock.Unlock()
@@ -674,3 +686,7 @@ func GetUpdatedCachePath(gluonDBPath, gluonCachePath string) string {
 
 	return strings.Replace(gluonCachePath, "/Users/"+cacheUsername+"/", "/Users/"+dbUsername+"/", 1)
 }
+
+func (bridge *Bridge) GetFeatureFlagValue(key string) bool {
+	return bridge.unleashService.GetFlagValue(key)
+}

internal/bridge/types.go

@@ -33,6 +33,7 @@ type Locator interface {
 	GetDependencyLicensesLink() string
 	Clear(...string) error
 	ProvideIMAPSyncConfigPath() (string, error)
+	ProvideUnleashCachePath() (string, error)
 }
 
 type ProxyController interface {

internal/bridge/unleash_test.go

@@ -0,0 +1,90 @@
+// Copyright (c) 2024 Proton AG
+//
+// This file is part of Proton Mail Bridge.
+//
+// Proton Mail Bridge is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Proton Mail Bridge is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Proton Mail Bridge. If not, see <https://www.gnu.org/licenses/>.
+
+package bridge_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/ProtonMail/go-proton-api"
+	"github.com/ProtonMail/go-proton-api/server"
+	"github.com/ProtonMail/proton-bridge/v3/internal/bridge"
+	"github.com/ProtonMail/proton-bridge/v3/internal/unleash"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_UnleashService(t *testing.T) {
+	withEnv(t, func(ctx context.Context, s *server.Server, netCtl *proton.NetCtl, locator bridge.Locator, storeKey []byte) {
+		unleash.ModifyPollPeriodAndJitter(500*time.Millisecond, 0)
+
+		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, storeKey, func(b *bridge.Bridge, _ *bridge.Mocks) {
+			// Initial startup assumes there is no cached feature flags.
+			require.Equal(t, b.GetFeatureFlagValue("test-1"), false)
+			require.Equal(t, b.GetFeatureFlagValue("test-2"), false)
+			require.Equal(t, b.GetFeatureFlagValue("test-3"), false)
+
+			s.PushFeatureFlag("test-1")
+			s.PushFeatureFlag("test-2")
+
+			// Wait for poll.
+			time.Sleep(time.Millisecond * 700)
+			require.Equal(t, b.GetFeatureFlagValue("test-1"), true)
+			require.Equal(t, b.GetFeatureFlagValue("test-2"), true)
+			require.Equal(t, b.GetFeatureFlagValue("test-3"), false)
+
+			s.PushFeatureFlag("test-3")
+			time.Sleep(time.Millisecond * 700) // Wait for poll again
+			require.Equal(t, b.GetFeatureFlagValue("test-1"), true)
+			require.Equal(t, b.GetFeatureFlagValue("test-2"), true)
+			require.Equal(t, b.GetFeatureFlagValue("test-3"), true)
+		})
+
+		// Wait for Bridge to close.
+		time.Sleep(time.Millisecond * 500)
+
+		// Second instance should have a feature flag cache file available. Therefore, all of the flags should evaluate to true on startup.
+		withBridge(ctx, t, s.GetHostURL(), netCtl, locator, storeKey, func(b *bridge.Bridge, _ *bridge.Mocks) {
+			require.Equal(t, b.GetFeatureFlagValue("test-1"), true)
+			require.Equal(t, b.GetFeatureFlagValue("test-2"), true)
+			require.Equal(t, b.GetFeatureFlagValue("test-3"), true)
+
+			s.DeleteFeatureFlags()
+
+			require.Equal(t, b.GetFeatureFlagValue("test-1"), true)
+			require.Equal(t, b.GetFeatureFlagValue("test-2"), true)
+			require.Equal(t, b.GetFeatureFlagValue("test-3"), true)
+
+			time.Sleep(time.Millisecond * 700)
+
+			require.Equal(t, b.GetFeatureFlagValue("test-1"), false)
+			require.Equal(t, b.GetFeatureFlagValue("test-2"), false)
+			require.Equal(t, b.GetFeatureFlagValue("test-3"), false)
+
+			s.PushFeatureFlag("test-3")
+			require.Equal(t, b.GetFeatureFlagValue("test-1"), false)
+			require.Equal(t, b.GetFeatureFlagValue("test-2"), false)
+			require.Equal(t, b.GetFeatureFlagValue("test-3"), false)
+
+			time.Sleep(time.Millisecond * 700)
+			require.Equal(t, b.GetFeatureFlagValue("test-1"), false)
+			require.Equal(t, b.GetFeatureFlagValue("test-2"), false)
+			require.Equal(t, b.GetFeatureFlagValue("test-3"), true)
+		})
+	})
+}