MM-7188: Cleaning push notification on every read, not only on channel switch (#9348)

* MM-7188: Cleaning push notification on every read, not only on channel switch

* Removed unnecesary goroutine

* Fixing tests

* Applying suggestion from PR

13 files changed, 238 insertions, 102 deletions

diff --git a/api4/channel.go b/api4/channel.go
index b29d2a94c..02a7c34b5 100644
--- a/api4/channel.go
+++ b/api4/channel.go
@@ -1073,7 +1073,7 @@ func addChannelMember(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	cm, err := c.App.AddChannelMember(member.UserId, channel, c.Session.UserId, postRootId)
+	cm, err := c.App.AddChannelMember(member.UserId, channel, c.Session.UserId, postRootId, !c.Session.IsMobileApp())
 	if err != nil {
 		c.Err = err
 		return
diff --git a/api4/post.go b/api4/post.go
index 6500cba32..7c116b7c7 100644
--- a/api4/post.go
+++ b/api4/post.go
@@ -58,7 +58,7 @@ func createPost(c *Context, w http.ResponseWriter, r *http.Request) {
 		post.CreateAt = 0
 	}
 
-	rp, err := c.App.CreatePostAsUser(c.App.PostWithProxyRemovedFromImageURLs(post))
+	rp, err := c.App.CreatePostAsUser(c.App.PostWithProxyRemovedFromImageURLs(post), !c.Session.IsMobileApp())
 	if err != nil {
 		c.Err = err
 		return
diff --git a/app/app.go b/app/app.go
index 511a464be..1c0d56a3c 100644
--- a/app/app.go
+++ b/app/app.go
@@ -50,6 +50,8 @@ type App struct {
 	Hubs                        []*Hub
 	HubsStopCheckingForDeadlock chan bool
 
+	PushNotificationsHub PushNotificationsHub
+
 	Jobs *jobs.JobServer
 
 	AccountMigration einterfaces.AccountMigrationInterface
@@ -128,6 +130,9 @@ func New(options ...Option) (outApp *App, outErr error) {
 
 	app.HTTPService = MakeHTTPService(app)
 
+	app.CreatePushNotificationsHub()
+	app.StartPushNotificationsHubWorkers()
+
 	defer func() {
 		if outErr != nil {
 			app.Shutdown()
@@ -276,6 +281,7 @@ func (a *App) Shutdown() {
 
 	a.StopServer()
 	a.HubStop()
+	a.StopPushNotificationsHubWorkers()
 
 	a.ShutDownPlugins()
 	a.WaitForGoroutines()
diff --git a/app/channel.go b/app/channel.go
index 166e5b4fe..84a334c66 100644
--- a/app/channel.go
+++ b/app/channel.go
@@ -817,7 +817,7 @@ func (a *App) AddUserToChannel(user *model.User, channel *model.Channel) (*model
 	return newMember, nil
 }
 
-func (a *App) AddChannelMember(userId string, channel *model.Channel, userRequestorId string, postRootId string) (*model.ChannelMember, *model.AppError) {
+func (a *App) AddChannelMember(userId string, channel *model.Channel, userRequestorId string, postRootId string, clearPushNotifications bool) (*model.ChannelMember, *model.AppError) {
 	if result := <-a.Srv.Store.Channel().GetMember(channel.Id, userId); result.Err != nil {
 		if result.Err.Id != store.MISSING_CHANNEL_MEMBER_ERROR {
 			return nil, result.Err
@@ -864,7 +864,7 @@ func (a *App) AddChannelMember(userId string, channel *model.Channel, userReques
 	}
 
 	if userRequestor != nil {
-		a.UpdateChannelLastViewedAt([]string{channel.Id}, userRequestor.Id)
+		a.MarkChannelsAsViewed([]string{channel.Id}, userRequestor.Id, clearPushNotifications)
 	}
 
 	return cm, nil
@@ -1559,6 +1559,55 @@ func (a *App) SearchChannelsUserNotIn(teamId string, userId string, term string)
 	return result.Data.(*model.ChannelList), nil
 }
 
+func (a *App) MarkChannelsAsViewed(channelIds []string, userId string, clearPushNotifications bool) (map[string]int64, *model.AppError) {
+	// I start looking for channels with notifications before I mark it as read, to clear the push notifications if needed
+	channelsToClearPushNotifications := []string{}
+	if *a.Config().EmailSettings.SendPushNotifications && clearPushNotifications {
+		for _, channelId := range channelIds {
+			if model.IsValidId(channelId) {
+				member := (<-a.Srv.Store.Channel().GetMember(channelId, userId)).Data.(*model.ChannelMember)
+				notify := member.NotifyProps[model.PUSH_NOTIFY_PROP]
+				if notify == model.CHANNEL_NOTIFY_DEFAULT {
+					user, _ := a.GetUser(userId)
+					notify = user.NotifyProps[model.PUSH_NOTIFY_PROP]
+				}
+				if notify == model.USER_NOTIFY_ALL {
+					if result := <-a.Srv.Store.User().GetAnyUnreadPostCountForChannel(userId, channelId); result.Err == nil {
+						if result.Data.(int64) > 0 {
+							channelsToClearPushNotifications = append(channelsToClearPushNotifications, channelId)
+						}
+					}
+				} else if notify == model.USER_NOTIFY_MENTION {
+					if result := <-a.Srv.Store.User().GetUnreadCountForChannel(userId, channelId); result.Err == nil {
+						if result.Data.(int64) > 0 {
+							channelsToClearPushNotifications = append(channelsToClearPushNotifications, channelId)
+						}
+					}
+				}
+			}
+		}
+	}
+	result := <-a.Srv.Store.Channel().UpdateLastViewedAt(channelIds, userId)
+	if result.Err != nil {
+		return nil, result.Err
+	}
+
+	times := result.Data.(map[string]int64)
+	if *a.Config().ServiceSettings.EnableChannelViewedMessages {
+		for _, channelId := range channelIds {
+			if model.IsValidId(channelId) {
+				message := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_CHANNEL_VIEWED, "", "", userId, nil)
+				message.Add("channel_id", channelId)
+				a.Publish(message)
+			}
+		}
+	}
+	for _, channelId := range channelsToClearPushNotifications {
+		a.ClearPushNotification(userId, channelId)
+	}
+	return times, nil
+}
+
 func (a *App) ViewChannel(view *model.ChannelView, userId string, clearPushNotifications bool) (map[string]int64, *model.AppError) {
 	if err := a.SetActiveChannel(userId, view.ChannelId); err != nil {
 		return nil, err
@@ -1570,45 +1619,15 @@ func (a *App) ViewChannel(view *model.ChannelView, userId string, clearPushNotif
 		channelIds = append(channelIds, view.ChannelId)
 	}
 
-	var pchan store.StoreChannel
 	if len(view.PrevChannelId) > 0 {
 		channelIds = append(channelIds, view.PrevChannelId)
-
-		if *a.Config().EmailSettings.SendPushNotifications && clearPushNotifications && len(view.ChannelId) > 0 {
-			pchan = a.Srv.Store.User().GetUnreadCountForChannel(userId, view.ChannelId)
-		}
 	}
 
 	if len(channelIds) == 0 {
 		return map[string]int64{}, nil
 	}
 
-	uchan := a.Srv.Store.Channel().UpdateLastViewedAt(channelIds, userId)
-
-	if pchan != nil {
-		result := <-pchan
-		if result.Err != nil {
-			return nil, result.Err
-		}
-		if result.Data.(int64) > 0 {
-			a.ClearPushNotification(userId, view.ChannelId)
-		}
-	}
-
-	var times map[string]int64
-	result := <-uchan
-	if result.Err != nil {
-		return nil, result.Err
-	}
-	times = result.Data.(map[string]int64)
-
-	if *a.Config().ServiceSettings.EnableChannelViewedMessages && model.IsValidId(view.ChannelId) {
-		message := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_CHANNEL_VIEWED, "", "", userId, nil)
-		message.Add("channel_id", view.ChannelId)
-		a.Publish(message)
-	}
-
-	return times, nil
+	return a.MarkChannelsAsViewed(channelIds, userId, clearPushNotifications)
 }
 
 func (a *App) PermanentDeleteChannel(channel *model.Channel) *model.AppError {
diff --git a/app/channel_test.go b/app/channel_test.go
index ba5f3eb58..4dc8dce37 100644
--- a/app/channel_test.go
+++ b/app/channel_test.go
@@ -389,7 +389,7 @@ func TestAddChannelMemberNoUserRequestor(t *testing.T) {
 	channel := th.createChannel(th.BasicTeam, model.CHANNEL_OPEN)
 	userRequestorId := ""
 	postRootId := ""
-	if _, err := th.App.AddChannelMember(user.Id, channel, userRequestorId, postRootId); err != nil {
+	if _, err := th.App.AddChannelMember(user.Id, channel, userRequestorId, postRootId, false); err != nil {
 		t.Fatal("Failed to add user to channel. Error: " + err.Message)
 	}
 
diff --git a/app/command_invite.go b/app/command_invite.go
index e6167dad6..1f6006018 100644
--- a/app/command_invite.go
+++ b/app/command_invite.go
@@ -135,7 +135,7 @@ func (me *InviteProvider) DoCommand(a *App, args *model.CommandArgs, message str
 		}
 	}
 
-	if _, err := a.AddChannelMember(userProfile.Id, channelToJoin, args.Session.UserId, ""); err != nil {
+	if _, err := a.AddChannelMember(userProfile.Id, channelToJoin, args.Session.UserId, "", !args.Session.IsMobileApp()); err != nil {
 		return &model.CommandResponse{
 			Text:         args.T("api.command_invite.fail.app_error"),
 			ResponseType: model.COMMAND_RESPONSE_TYPE_EPHEMERAL,
diff --git a/app/notification_push.go b/app/notification_push.go
index 5c7df0da7..0a24ba1e0 100644
--- a/app/notification_push.go
+++ b/app/notification_push.go
@@ -5,9 +5,9 @@ package app
 
 import (
 	"fmt"
+	"hash/fnv"
 	"net/http"
 	"strings"
-	"time"
 
 	"github.com/mattermost/mattermost-server/mlog"
 	"github.com/mattermost/mattermost-server/model"
@@ -15,21 +15,42 @@ import (
 	"github.com/nicksnyder/go-i18n/i18n"
 )
 
-func (a *App) sendPushNotification(notification *postNotification, user *model.User, explicitMention, channelWideMention bool, replyToThreadType string) *model.AppError {
-	channel := notification.channel
-	post := notification.post
+type NotificationType string
 
-	cfg := a.Config()
+const NOTIFICATION_TYPE_CLEAR NotificationType = "clear"
+const NOTIFICATION_TYPE_MESSAGE NotificationType = "message"
 
-	var nameFormat string
-	if result := <-a.Srv.Store.Preference().Get(user.Id, model.PREFERENCE_CATEGORY_DISPLAY_SETTINGS, model.PREFERENCE_NAME_NAME_FORMAT); result.Err != nil {
-		nameFormat = *a.Config().TeamSettings.TeammateNameDisplay
-	} else {
-		nameFormat = result.Data.(model.Preference).Value
-	}
+const PUSH_NOTIFICATION_HUB_WORKERS = 1000
+const PUSH_NOTIFICATIONS_HUB_BUFFER_PER_WORKER = 50
 
-	channelName := notification.GetChannelName(nameFormat, user.Id)
-	senderName := notification.GetSenderName(nameFormat, cfg.ServiceSettings.EnablePostUsernameOverride)
+type PushNotificationsHub struct {
+	Channels []chan PushNotification
+}
+
+type PushNotification struct {
+	notificationType   NotificationType
+	userId             string
+	channelId          string
+	post               *model.Post
+	user               *model.User
+	channel            *model.Channel
+	senderName         string
+	channelName        string
+	explicitMention    bool
+	channelWideMention bool
+	replyToThreadType  string
+}
+
+func (hub *PushNotificationsHub) GetGoChannelFromUserId(userId string) chan PushNotification {
+	h := fnv.New32a()
+	h.Write([]byte(userId))
+	chanIdx := h.Sum32() % PUSH_NOTIFICATION_HUB_WORKERS
+	return hub.Channels[chanIdx]
+}
+
+func (a *App) sendPushNotificationSync(post *model.Post, user *model.User, channel *model.Channel, channelName string, senderName string,
+	explicitMention, channelWideMention bool, replyToThreadType string) *model.AppError {
+	cfg := a.Config()
 
 	sessions, err := a.getMobileAppSessions(user.Id)
 	if err != nil {
@@ -86,11 +107,7 @@ func (a *App) sendPushNotification(notification *postNotification, user *model.U
 
 		mlog.Debug(fmt.Sprintf("Sending push notification to device %v for user %v with msg of '%v'", tmpMessage.DeviceId, user.Id, msg.Message), mlog.String("user_id", user.Id))
 
-		a.Go(func(session *model.Session) func() {
-			return func() {
-				a.sendToPushProxy(tmpMessage, session)
-			}
-		}(session))
+		a.sendToPushProxy(tmpMessage, session)
 
 		if a.Metrics != nil {
 			a.Metrics.IncrementPostSentPush()
@@ -100,6 +117,35 @@ func (a *App) sendPushNotification(notification *postNotification, user *model.U
 	return nil
 }
 
+func (a *App) sendPushNotification(notification *postNotification, user *model.User, explicitMention, channelWideMention bool, replyToThreadType string) {
+	cfg := a.Config()
+	channel := notification.channel
+	post := notification.post
+
+	var nameFormat string
+	if result := <-a.Srv.Store.Preference().Get(user.Id, model.PREFERENCE_CATEGORY_DISPLAY_SETTINGS, model.PREFERENCE_NAME_NAME_FORMAT); result.Err != nil {
+		nameFormat = *a.Config().TeamSettings.TeammateNameDisplay
+	} else {
+		nameFormat = result.Data.(model.Preference).Value
+	}
+
+	channelName := notification.GetChannelName(nameFormat, user.Id)
+	senderName := notification.GetSenderName(nameFormat, cfg.ServiceSettings.EnablePostUsernameOverride)
+
+	c := a.PushNotificationsHub.GetGoChannelFromUserId(user.Id)
+	c <- PushNotification{
+		notificationType:   NOTIFICATION_TYPE_MESSAGE,
+		post:               post,
+		user:               user,
+		channel:            channel,
+		senderName:         senderName,
+		channelName:        channelName,
+		explicitMention:    explicitMention,
+		channelWideMention: channelWideMention,
+		replyToThreadType:  replyToThreadType,
+	}
+}
+
 func (a *App) getPushNotificationMessage(postMessage string, explicitMention, channelWideMention, hasFiles bool,
 	senderName, channelName, channelType, replyToThreadType string, userLocale i18n.TranslateFunc) string {
 	message := ""
@@ -140,41 +186,85 @@ func (a *App) getPushNotificationMessage(postMessage string, explicitMention, ch
 	return message
 }
 
+func (a *App) ClearPushNotificationSync(userId string, channelId string) {
+	sessions, err := a.getMobileAppSessions(userId)
+	if err != nil {
+		mlog.Error(err.Error())
+		return
+	}
+
+	msg := model.PushNotification{}
+	msg.Type = model.PUSH_TYPE_CLEAR
+	msg.ChannelId = channelId
+	msg.ContentAvailable = 0
+	if badge := <-a.Srv.Store.User().GetUnreadCount(userId); badge.Err != nil {
+		msg.Badge = 0
+		mlog.Error(fmt.Sprint("We could not get the unread message count for the user", userId, badge.Err), mlog.String("user_id", userId))
+	} else {
+		msg.Badge = int(badge.Data.(int64))
+	}
+
+	mlog.Debug(fmt.Sprintf("Clearing push notification to %v with channel_id %v", msg.DeviceId, msg.ChannelId))
+
+	for _, session := range sessions {
+		tmpMessage := *model.PushNotificationFromJson(strings.NewReader(msg.ToJson()))
+		tmpMessage.SetDeviceIdAndPlatform(session.DeviceId)
+		a.sendToPushProxy(tmpMessage, session)
+	}
+}
+
 func (a *App) ClearPushNotification(userId string, channelId string) {
-	a.Go(func() {
-		// Sleep is to allow the read replicas a chance to fully sync
-		// the unread count for sending an accurate count.
-		// Delaying a little doesn't hurt anything and is cheaper than
-		// attempting to read from master.
-		time.Sleep(time.Second * 5)
-
-		sessions, err := a.getMobileAppSessions(userId)
-		if err != nil {
-			mlog.Error(err.Error())
-			return
-		}
+	channel := a.PushNotificationsHub.GetGoChannelFromUserId(userId)
+	channel <- PushNotification{
+		notificationType: NOTIFICATION_TYPE_CLEAR,
+		userId:           userId,
+		channelId:        channelId,
+	}
+}
 
-		msg := model.PushNotification{}
-		msg.Type = model.PUSH_TYPE_CLEAR
-		msg.ChannelId = channelId
-		msg.ContentAvailable = 0
-		if badge := <-a.Srv.Store.User().GetUnreadCount(userId); badge.Err != nil {
-			msg.Badge = 0
-			mlog.Error(fmt.Sprint("We could not get the unread message count for the user", userId, badge.Err), mlog.String("user_id", userId))
-		} else {
-			msg.Badge = int(badge.Data.(int64))
+func (a *App) CreatePushNotificationsHub() {
+	hub := PushNotificationsHub{
+		Channels: []chan PushNotification{},
+	}
+	for x := 0; x < PUSH_NOTIFICATION_HUB_WORKERS; x++ {
+		hub.Channels = append(hub.Channels, make(chan PushNotification, PUSH_NOTIFICATIONS_HUB_BUFFER_PER_WORKER))
+	}
+	a.PushNotificationsHub = hub
+}
+
+func (a *App) pushNotificationWorker(notifications chan PushNotification) {
+	for notification := range notifications {
+		switch notification.notificationType {
+		case NOTIFICATION_TYPE_CLEAR:
+			a.ClearPushNotificationSync(notification.userId, notification.channelId)
+		case NOTIFICATION_TYPE_MESSAGE:
+			a.sendPushNotificationSync(
+				notification.post,
+				notification.user,
+				notification.channel,
+				notification.channelName,
+				notification.senderName,
+				notification.explicitMention,
+				notification.channelWideMention,
+				notification.replyToThreadType,
+			)
+		default:
+			mlog.Error(fmt.Sprintf("Invalid notification type %v", notification.notificationType))
 		}
+	}
+}
 
-		mlog.Debug(fmt.Sprintf("Clearing push notification to %v with channel_id %v", msg.DeviceId, msg.ChannelId))
+func (a *App) StartPushNotificationsHubWorkers() {
+	for x := 0; x < PUSH_NOTIFICATION_HUB_WORKERS; x++ {
+		channel := a.PushNotificationsHub.Channels[x]
+		a.Go(func() { a.pushNotificationWorker(channel) })
+	}
+}
 
-		for _, session := range sessions {
-			tmpMessage := *model.PushNotificationFromJson(strings.NewReader(msg.ToJson()))
-			tmpMessage.SetDeviceIdAndPlatform(session.DeviceId)
-			a.Go(func() {
-				a.sendToPushProxy(tmpMessage, session)
-			})
-		}
-	})
+func (a *App) StopPushNotificationsHubWorkers() {
+	for _, channel := range a.PushNotificationsHub.Channels {
+		close(channel)
+	}
 }
 
 func (a *App) sendToPushProxy(msg model.PushNotification, session *model.Session) {
diff --git a/app/plugin_api.go b/app/plugin_api.go
index 20a27316f..4fc8126f1 100644
--- a/app/plugin_api.go
+++ b/app/plugin_api.go
@@ -251,7 +251,7 @@ func (api *PluginAPI) AddChannelMember(channelId, userId string) (*model.Channel
 		return nil, err
 	}
 
-	return api.app.AddChannelMember(userId, channel, userRequestorId, postRootId)
+	return api.app.AddChannelMember(userId, channel, userRequestorId, postRootId, false)
 }
 
 func (api *PluginAPI) GetChannelMember(channelId, userId string) (*model.ChannelMember, *model.AppError) {
diff --git a/app/post.go b/app/post.go
index 1daad6eea..fc941a68f 100644
--- a/app/post.go
+++ b/app/post.go
@@ -24,7 +24,7 @@ import (
 	"golang.org/x/net/html/charset"
 )
 
-func (a *App) CreatePostAsUser(post *model.Post) (*model.Post, *model.AppError) {
+func (a *App) CreatePostAsUser(post *model.Post, clearPushNotifications bool) (*model.Post, *model.AppError) {
 	// Check that channel has not been deleted
 	var channel *model.Channel
 	if result := <-a.Srv.Store.Channel().Get(post.ChannelId, true); result.Err != nil {
@@ -78,14 +78,8 @@ func (a *App) CreatePostAsUser(post *model.Post) (*model.Post, *model.AppError)
 	} else {
 		// Update the LastViewAt only if the post does not have from_webhook prop set (eg. Zapier app)
 		if _, ok := post.Props["from_webhook"]; !ok {
-			if result := <-a.Srv.Store.Channel().UpdateLastViewedAt([]string{post.ChannelId}, post.UserId); result.Err != nil {
-				mlog.Error(fmt.Sprintf("Encountered error updating last viewed, channel_id=%s, user_id=%s, err=%v", post.ChannelId, post.UserId, result.Err))
-			}
-
-			if *a.Config().ServiceSettings.EnableChannelViewedMessages {
-				message := model.NewWebSocketEvent(model.WEBSOCKET_EVENT_CHANNEL_VIEWED, "", "", post.UserId, nil)
-				message.Add("channel_id", post.ChannelId)
-				a.Publish(message)
+			if _, err := a.MarkChannelsAsViewed([]string{post.ChannelId}, post.UserId, clearPushNotifications); err != nil {
+				mlog.Error(fmt.Sprintf("Encountered error updating last viewed, channel_id=%s, user_id=%s, err=%v", post.ChannelId, post.UserId, err))
 			}
 		}
 
diff --git a/app/post_test.go b/app/post_test.go
index 2dce8bab8..5d93d3f0f 100644
--- a/app/post_test.go
+++ b/app/post_test.go
@@ -115,7 +115,7 @@ func TestPostReplyToPostWhereRootPosterLeftChannel(t *testing.T) {
 		CreateAt:      0,
 	}
 
-	if _, err := th.App.CreatePostAsUser(&replyPost); err != nil {
+	if _, err := th.App.CreatePostAsUser(&replyPost, false); err != nil {
 		t.Fatal(err)
 	}
 }
@@ -175,7 +175,7 @@ func TestPostAction(t *testing.T) {
 		},
 	}
 
-	post, err := th.App.CreatePostAsUser(&interactivePost)
+	post, err := th.App.CreatePostAsUser(&interactivePost, false)
 	require.Nil(t, err)
 
 	attachments, ok := post.Props["attachments"].([]*model.SlackAttachment)
@@ -212,7 +212,7 @@ func TestPostAction(t *testing.T) {
 		},
 	}
 
-	post2, err := th.App.CreatePostAsUser(&menuPost)
+	post2, err := th.App.CreatePostAsUser(&menuPost, false)
 	require.Nil(t, err)
 
 	attachments2, ok := post2.Props["attachments"].([]*model.SlackAttachment)
@@ -267,7 +267,7 @@ func TestPostAction(t *testing.T) {
 		},
 	}
 
-	postplugin, err := th.App.CreatePostAsUser(&interactivePostPlugin)
+	postplugin, err := th.App.CreatePostAsUser(&interactivePostPlugin, false)
 	require.Nil(t, err)
 
 	attachmentsPlugin, ok := postplugin.Props["attachments"].([]*model.SlackAttachment)
@@ -308,7 +308,7 @@ func TestPostAction(t *testing.T) {
 		},
 	}
 
-	postSiteURL, err := th.App.CreatePostAsUser(&interactivePostSiteURL)
+	postSiteURL, err := th.App.CreatePostAsUser(&interactivePostSiteURL, false)
 	require.Nil(t, err)
 
 	attachmentsSiteURL, ok := postSiteURL.Props["attachments"].([]*model.SlackAttachment)
@@ -350,7 +350,7 @@ func TestPostAction(t *testing.T) {
 		},
 	}
 
-	postSubpath, err := th.App.CreatePostAsUser(&interactivePostSubpath)
+	postSubpath, err := th.App.CreatePostAsUser(&interactivePostSubpath, false)
 	require.Nil(t, err)
 
 	attachmentsSubpath, ok := postSubpath.Props["attachments"].([]*model.SlackAttachment)
@@ -389,7 +389,7 @@ func TestPostChannelMentions(t *testing.T) {
 		CreateAt:      0,
 	}
 
-	result, err := th.App.CreatePostAsUser(post)
+	result, err := th.App.CreatePostAsUser(post, false)
 	require.Nil(t, err)
 	assert.Equal(t, map[string]interface{}{
 		"mention-test": map[string]interface{}{
diff --git a/store/sqlstore/user_store.go b/store/sqlstore/user_store.go
index 900010ce4..941aa60e9 100644
--- a/store/sqlstore/user_store.go
+++ b/store/sqlstore/user_store.go
@@ -949,6 +949,16 @@ func (us SqlUserStore) GetUnreadCountForChannel(userId string, channelId string)
 	})
 }
 
+func (us SqlUserStore) GetAnyUnreadPostCountForChannel(userId string, channelId string) store.StoreChannel {
+	return store.Do(func(result *store.StoreResult) {
+		if count, err := us.GetReplica().SelectInt("SELECT SUM(c.TotalMsgCount - cm.MsgCount) FROM Channels c INNER JOIN ChannelMembers cm ON c.Id = :ChannelId AND cm.ChannelId = :ChannelId AND cm.UserId = :UserId", map[string]interface{}{"ChannelId": channelId, "UserId": userId}); err != nil {
+			result.Err = model.NewAppError("SqlUserStore.GetMentionCountForChannel", "store.sql_user.get_unread_count_for_channel.app_error", nil, err.Error(), http.StatusInternalServerError)
+		} else {
+			result.Data = count
+		}
+	})
+}
+
 func (us SqlUserStore) Search(teamId string, term string, options map[string]bool) store.StoreChannel {
 	return store.Do(func(result *store.StoreResult) {
 		searchQuery := ""
diff --git a/store/store.go b/store/store.go
index 8073b9437..608d501c0 100644
--- a/store/store.go
+++ b/store/store.go
@@ -265,6 +265,7 @@ type UserStore interface {
 	AnalyticsActiveCount(time int64) StoreChannel
 	GetUnreadCount(userId string) StoreChannel
 	GetUnreadCountForChannel(userId string, channelId string) StoreChannel
+	GetAnyUnreadPostCountForChannel(userId string, channelId string) StoreChannel
 	GetRecentlyActiveUsersForTeam(teamId string, offset, limit int) StoreChannel
 	GetNewUsersForTeam(teamId string, offset, limit int) StoreChannel
 	Search(teamId string, term string, options map[string]bool) StoreChannel
diff --git a/store/storetest/mocks/UserStore.go b/store/storetest/mocks/UserStore.go
index 51c37cb20..b505a2f0b 100644
--- a/store/storetest/mocks/UserStore.go
+++ b/store/storetest/mocks/UserStore.go
@@ -194,6 +194,22 @@ func (_m *UserStore) GetAllUsingAuthService(authService string) store.StoreChann
 	return r0
 }
 
+// GetAnyUnreadPostCountForChannel provides a mock function with given fields: userId, channelId
+func (_m *UserStore) GetAnyUnreadPostCountForChannel(userId string, channelId string) store.StoreChannel {
+	ret := _m.Called(userId, channelId)
+
+	var r0 store.StoreChannel
+	if rf, ok := ret.Get(0).(func(string, string) store.StoreChannel); ok {
+		r0 = rf(userId, channelId)
+	} else {
+		if ret.Get(0) != nil {
+			r0 = ret.Get(0).(store.StoreChannel)
+		}
+	}
+
+	return r0
+}
+
 // GetByAuth provides a mock function with given fields: authData, authService
 func (_m *UserStore) GetByAuth(authData *string, authService string) store.StoreChannel {
 	ret := _m.Called(authData, authService)