MM-52600: [Shared Channels] Shared channels do not sync channel membership (#30976)

server/public/model/channel.go

@@ -507,3 +507,15 @@ type GroupMessageConversionRequestBody struct {
 	Name        string `json:"name"`
 	DisplayName string `json:"display_name"`
 }
+
+// ChannelMembersGetOptions provides parameters for getting channel members
+type ChannelMembersGetOptions struct {
+	// ChannelID specifies which channel to get members for
+	ChannelID string
+	// Offset for pagination
+	Offset int
+	// Limit for pagination (maximum number of results to return)
+	Limit int
+	// UpdatedAfter filters members updated after the given timestamp (cursor-based pagination)
+	UpdatedAfter int64
+}

server/public/model/config.go

@@ -49,7 +49,8 @@ const (
 	PasswordMaximumLength = 72
 	PasswordMinimumLength = 5
 
-	ServiceGitlab    = "gitlab"
+	ServiceGitlab = "gitlab"
+
 	ServiceGoogle    = "google"
 	ServiceOffice365 = "office365"
 	ServiceOpenid    = "openid"
@@ -285,7 +286,8 @@ const (
 
 	LocalModeSocketPath = "/var/tmp/mattermost_local.socket"
 
-	ConnectedWorkspacesSettingsDefaultMaxPostsPerSync = 50 // a bit more than 4 typical screenfulls of posts
+	ConnectedWorkspacesSettingsDefaultMaxPostsPerSync     = 50 // a bit more than 4 typical screenfulls of posts
+	ConnectedWorkspacesSettingsDefaultMemberSyncBatchSize = 20 // optimal batch size for syncing channel members
 
 	// These storage classes are the valid values for the x-amz-storage-class header. More documentation here https://docs.aws.amazon.com/AmazonS3/latest/API/API_PutObject.html#AmazonS3-PutObject-request-header-StorageClass
 	StorageClassStandard           = "STANDARD"
@@ -3462,6 +3464,7 @@ type ConnectedWorkspacesSettings struct {
 	SyncUsersOnConnectionOpen       *bool
 	GlobalUserSyncBatchSize         *int
 	MaxPostsPerSync                 *int
+	MemberSyncBatchSize             *int // Maximum number of members to process in a single batch during shared channel synchronization
 }
 
 func (c *ConnectedWorkspacesSettings) SetDefaults(isUpdate bool, e ExperimentalSettings) {
@@ -3496,6 +3499,10 @@ func (c *ConnectedWorkspacesSettings) SetDefaults(isUpdate bool, e ExperimentalS
 	if c.MaxPostsPerSync == nil {
 		c.MaxPostsPerSync = NewPointer(ConnectedWorkspacesSettingsDefaultMaxPostsPerSync)
 	}
+
+	if c.MemberSyncBatchSize == nil {
+		c.MemberSyncBatchSize = NewPointer(ConnectedWorkspacesSettingsDefaultMemberSyncBatchSize)
+	}
 }
 
 type GlobalRelayMessageExportSettings struct {

server/public/model/feature_flags.go

@@ -25,6 +25,9 @@ type FeatureFlags struct {
 	// Enable plugins in shared channels.
 	EnableSharedChannelsPlugins bool
 
+	// Enable synchronization of channel members in shared channels
+	EnableSharedChannelsMemberSync bool
+
 	// Enable syncing all users for remote clusters in shared channels
 	EnableSyncAllUsersForRemoteCluster bool
 
@@ -72,6 +75,7 @@ func (f *FeatureFlags) SetDefaults() {
 	f.TestBoolFeature = false
 	f.EnableRemoteClusterService = false
 	f.EnableSharedChannelsDMs = false
+	f.EnableSharedChannelsMemberSync = false
 	f.EnableSyncAllUsersForRemoteCluster = false
 	f.EnableSharedChannelsPlugins = true
 	f.AppsEnabled = false

server/public/model/shared_channel.go

@@ -118,6 +118,7 @@ type SharedChannelRemote struct {
 	LastPostUpdateID  string `json:"last_post_id"`
 	LastPostCreateAt  int64  `json:"last_post_create_at"`
 	LastPostCreateID  string `json:"last_post_create_id"`
+	LastMembersSyncAt int64  `json:"last_members_sync_at"`
 }
 
 func (sc *SharedChannelRemote) IsValid() *AppError {
@@ -169,12 +170,13 @@ type SharedChannelRemoteStatus struct {
 // SharedChannelUser stores a lastSyncAt timestamp on behalf of a remote cluster for
 // each user that has been synchronized.
 type SharedChannelUser struct {
-	Id         string `json:"id"`
-	UserId     string `json:"user_id"`
-	ChannelId  string `json:"channel_id"`
-	RemoteId   string `json:"remote_id"`
-	CreateAt   int64  `json:"create_at"`
-	LastSyncAt int64  `json:"last_sync_at"`
+	Id                   string `json:"id"`
+	UserId               string `json:"user_id"`
+	ChannelId            string `json:"channel_id"`
+	RemoteId             string `json:"remote_id"`
+	CreateAt             int64  `json:"create_at"`
+	LastSyncAt           int64  `json:"last_sync_at"`
+	LastMembershipSyncAt int64  `json:"last_membership_sync_at"`
 }
 
 func (scu *SharedChannelUser) PreSave() {
@@ -270,15 +272,25 @@ type SharedChannelRemoteFilterOpts struct {
 	IncludeDeleted     bool
 }
 
+// MembershipChangeMsg represents a change in channel membership
+type MembershipChangeMsg struct {
+	ChannelId  string `json:"channel_id"`
+	UserId     string `json:"user_id"`
+	IsAdd      bool   `json:"is_add"`
+	RemoteId   string `json:"remote_id"`
+	ChangeTime int64  `json:"change_time"`
+}
+
 // SyncMsg represents a change in content (post add/edit/delete, reaction add/remove, users).
 // It is sent to remote clusters as the payload of a `RemoteClusterMsg`.
 type SyncMsg struct {
-	Id        string           `json:"id"`
-	ChannelId string           `json:"channel_id"`
-	Users     map[string]*User `json:"users,omitempty"`
-	Posts     []*Post          `json:"posts,omitempty"`
-	Reactions []*Reaction      `json:"reactions,omitempty"`
-	Statuses  []*Status        `json:"statuses,omitempty"`
+	Id                string                 `json:"id"`
+	ChannelId         string                 `json:"channel_id"`
+	Users             map[string]*User       `json:"users,omitempty"`
+	Posts             []*Post                `json:"posts,omitempty"`
+	Reactions         []*Reaction            `json:"reactions,omitempty"`
+	Statuses          []*Status              `json:"statuses,omitempty"`
+	MembershipChanges []*MembershipChangeMsg `json:"membership_changes,omitempty"`
 }
 
 func NewSyncMsg(channelID string) *SyncMsg {