Mono repo -> Master (#22553)

Combines the following repositories into one:

https://github.com/mattermost/mattermost-server
https://github.com/mattermost/mattermost-webapp
https://github.com/mattermost/focalboard
https://github.com/mattermost/mattermost-plugin-playbooks

server/channels/app/platform/feature_flags.go

@@ -0,0 +1,118 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package platform
+
+import (
+	"encoding/json"
+	"os"
+	"time"
+
+	"github.com/mattermost/mattermost-server/v6/server/channels/app/featureflag"
+	"github.com/mattermost/mattermost-server/v6/server/platform/shared/mlog"
+)
+
+// SetupFeatureFlags called on startup and when the cluster leader changes.
+// Starts or stops the synchronization of feature flags from upstream management.
+func (ps *PlatformService) SetupFeatureFlags() {
+	ps.featureFlagSynchronizerMutex.Lock()
+	defer ps.featureFlagSynchronizerMutex.Unlock()
+	splitKey := *ps.Config().ServiceSettings.SplitKey
+	splitConfigured := splitKey != ""
+	syncFeatureFlags := splitConfigured && ps.IsLeader()
+
+	ps.configStore.SetReadOnlyFF(!splitConfigured)
+
+	if syncFeatureFlags {
+		if err := ps.startFeatureFlagUpdateJob(); err != nil {
+			ps.logger.Warn("Unable to setup synchronization with feature flag management. Will fallback to cache.", mlog.Err(err))
+		}
+	} else {
+		ps.StopFeatureFlagUpdateJob()
+	}
+
+	if err := ps.configStore.Load(); err != nil {
+		ps.logger.Warn("Unable to load config store after feature flag setup.", mlog.Err(err))
+	}
+}
+
+func (ps *PlatformService) updateFeatureFlagValuesFromManagement() {
+	newCfg := ps.configStore.GetNoEnv().Clone()
+	oldFlags := *newCfg.FeatureFlags
+	newFlags := ps.featureFlagSynchronizer.UpdateFeatureFlagValues(oldFlags)
+	oldFlagsBytes, _ := json.Marshal(oldFlags)
+	newFlagsBytes, _ := json.Marshal(newFlags)
+	ps.logger.Debug("Checking feature flags from management service", mlog.String("old_flags", string(oldFlagsBytes)), mlog.String("new_flags", string(newFlagsBytes)))
+	if oldFlags != newFlags {
+		ps.logger.Debug("Feature flag change detected, updating config")
+		*newCfg.FeatureFlags = newFlags
+		ps.SaveConfig(newCfg, true)
+	}
+}
+
+func (ps *PlatformService) startFeatureFlagUpdateJob() error {
+	// Can be run multiple times
+	if ps.featureFlagSynchronizer != nil {
+		return nil
+	}
+
+	var log *mlog.Logger
+	if *ps.Config().ServiceSettings.DebugSplit {
+		log = ps.logger
+	}
+
+	attributes := map[string]any{}
+
+	// if we are part of a cloud installation, add its installation and group id
+	if installationId := os.Getenv("MM_CLOUD_INSTALLATION_ID"); installationId != "" {
+		attributes["installation_id"] = installationId
+	}
+	if groupId := os.Getenv("MM_CLOUD_GROUP_ID"); groupId != "" {
+		attributes["group_id"] = groupId
+	}
+
+	synchronizer, err := featureflag.NewSynchronizer(featureflag.SyncParams{
+		ServerID:   ps.telemetryId,
+		SplitKey:   *ps.Config().ServiceSettings.SplitKey,
+		Log:        log,
+		Attributes: attributes,
+	})
+	if err != nil {
+		return err
+	}
+
+	ps.featureFlagStop = make(chan struct{})
+	ps.featureFlagStopped = make(chan struct{})
+	ps.featureFlagSynchronizer = synchronizer
+	syncInterval := *ps.Config().ServiceSettings.FeatureFlagSyncIntervalSeconds
+
+	go func() {
+		ticker := time.NewTicker(time.Duration(syncInterval) * time.Second)
+		defer ticker.Stop()
+		defer close(ps.featureFlagStopped)
+		if err := synchronizer.EnsureReady(); err != nil {
+			ps.logger.Warn("Problem connecting to feature flag management. Will fallback to cloud cache.", mlog.Err(err))
+			return
+		}
+		ps.updateFeatureFlagValuesFromManagement()
+		for {
+			select {
+			case <-ps.featureFlagStop:
+				return
+			case <-ticker.C:
+				ps.updateFeatureFlagValuesFromManagement()
+			}
+		}
+	}()
+
+	return nil
+}
+
+func (ps *PlatformService) StopFeatureFlagUpdateJob() {
+	if ps.featureFlagSynchronizer != nil {
+		close(ps.featureFlagStop)
+		<-ps.featureFlagStopped
+		ps.featureFlagSynchronizer.Close()
+		ps.featureFlagSynchronizer = nil
+	}
+}