MM-30882: Fix read-after-write issue for demoting user (#16911)

* MM-30882: Fix read-after-write issue for demoting user

In (*App).DemoteUserToGuest, we would demote a user, and then immediately
read it back to do future operations from the user. This reading back
of the user had the effect of sticking the old value into the cache
after which it would never be updated.

There was another issue along with this, which was when the invalidation
message would broadcast across the cluster, it would hit the cache invalidation
problem where an unrelated store call would miss the cache because
it was invalidated, and then again read from replica and stick the old value.

To fix all these, we return the new value directly from the store method
to avoid having the app to read it again.

And we add a map in the localcache layer which tracks invalidations made,
and then switch to use master if it's true.

The core change is fairly limited, but due to changing the store method signatures,
a lot of code needed to be updated to pass "context.Background". Therefore the PR
just "appears" to be big, but the main changes are limited to app/user.go,
sqlstore/user_store.go and user_layer.go

https://mattermost.atlassian.net/browse/MM-30882

```release-note
Fix an issue where demoting a user to guest would not take effect in
an environment with read replicas.
```

* Fix concurrent map access

* Fixing mistakes

* fix tests

app/bot.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -55,7 +56,7 @@ func (a *App) CreateBot(bot *model.Bot) (*model.Bot, *model.AppError) {
 	}
 
 	// Get the owner of the bot, if one exists. If not, don't send a message
-	ownerUser, err := a.Srv().Store.User().Get(bot.OwnerId)
+	ownerUser, err := a.Srv().Store.User().Get(context.Background(), bot.OwnerId)
 	var nfErr *store.ErrNotFound
 	if err != nil && !errors.As(err, &nfErr) {
 		return nil, model.NewAppError("CreateBot", "app.user.get.app_error", nil, err.Error(), http.StatusInternalServerError)
@@ -156,7 +157,7 @@ func (a *App) PatchBot(botUserId string, botPatch *model.BotPatch) (*model.Bot,
 
 	bot.Patch(botPatch)
 
-	user, nErr := a.Srv().Store.User().Get(botUserId)
+	user, nErr := a.Srv().Store.User().Get(context.Background(), botUserId)
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
 		switch {
@@ -233,7 +234,7 @@ func (a *App) GetBots(options *model.BotGetOptions) (model.BotList, *model.AppEr
 
 // UpdateBotActive marks a bot as active or inactive, along with its corresponding user.
 func (a *App) UpdateBotActive(botUserId string, active bool) (*model.Bot, *model.AppError) {
-	user, nErr := a.Srv().Store.User().Get(botUserId)
+	user, nErr := a.Srv().Store.User().Get(context.Background(), botUserId)
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
 		switch {

app/channel.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"net/http"
@@ -67,7 +68,7 @@ func (a *App) JoinDefaultChannels(teamID string, user *model.User, shouldBeAdmin
 	var requestor *model.User
 	var nErr error
 	if userRequestorId != "" {
-		requestor, nErr = a.Srv().Store.User().Get(userRequestorId)
+		requestor, nErr = a.Srv().Store.User().Get(context.Background(), userRequestorId)
 		if nErr != nil {
 			var nfErr *store.ErrNotFound
 			switch {
@@ -264,7 +265,7 @@ func (a *App) CreateChannel(channel *model.Channel, addMember bool) (*model.Chan
 	}
 
 	if addMember {
-		user, nErr := a.Srv().Store.User().Get(channel.CreatorId)
+		user, nErr := a.Srv().Store.User().Get(context.Background(), channel.CreatorId)
 		if nErr != nil {
 			var nfErr *store.ErrNotFound
 			switch {
@@ -386,7 +387,7 @@ func (a *App) handleCreationEvent(userID, otherUserID string, channel *model.Cha
 }
 
 func (a *App) createDirectChannel(userID, otherUserID string) (*model.Channel, *model.AppError) {
-	users, err := a.Srv().Store.User().GetMany([]string{userID, otherUserID})
+	users, err := a.Srv().Store.User().GetMany(context.Background(), []string{userID, otherUserID})
 	if err != nil {
 		return nil, model.NewAppError("CreateDirectChannel", "api.channel.create_direct_channel.invalid_user.app_error", nil, err.Error(), http.StatusBadRequest)
 	}
@@ -520,7 +521,7 @@ func (a *App) createGroupChannel(userIDs []string) (*model.Channel, *model.AppEr
 		return nil, model.NewAppError("CreateGroupChannel", "api.channel.create_group.bad_size.app_error", nil, "", http.StatusBadRequest)
 	}
 
-	users, err := a.Srv().Store.User().GetProfileByIds(userIDs, nil, true)
+	users, err := a.Srv().Store.User().GetProfileByIds(context.Background(), userIDs, nil, true)
 	if err != nil {
 		return nil, model.NewAppError("createGroupChannel", "app.user.get_profiles.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
@@ -599,7 +600,7 @@ func (a *App) GetGroupChannel(userIDs []string) (*model.Channel, *model.AppError
 		return nil, model.NewAppError("GetGroupChannel", "api.channel.create_group.bad_size.app_error", nil, "", http.StatusBadRequest)
 	}
 
-	users, err := a.Srv().Store.User().GetProfileByIds(userIDs, nil, true)
+	users, err := a.Srv().Store.User().GetProfileByIds(context.Background(), userIDs, nil, true)
 	if err != nil {
 		return nil, model.NewAppError("GetGroupChannel", "app.user.get_profiles.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
@@ -745,7 +746,7 @@ func (a *App) RestoreChannel(channel *model.Channel, userID string) (*model.Chan
 	message.Add("channel_id", channel.Id)
 	a.Publish(message)
 
-	user, nErr := a.Srv().Store.User().Get(userID)
+	user, nErr := a.Srv().Store.User().Get(context.Background(), userID)
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
 		switch {
@@ -1236,7 +1237,7 @@ func (a *App) DeleteChannel(channel *model.Channel, userID string) *model.AppErr
 	var user *model.User
 	if userID != "" {
 		var nErr error
-		user, nErr = a.Srv().Store.User().Get(userID)
+		user, nErr = a.Srv().Store.User().Get(context.Background(), userID)
 		if nErr != nil {
 			var nfErr *store.ErrNotFound
 			switch {
@@ -1492,7 +1493,7 @@ func (a *App) AddDirectChannels(teamID string, user *model.User) *model.AppError
 }
 
 func (a *App) PostUpdateChannelHeaderMessage(userID string, channel *model.Channel, oldChannelHeader, newChannelHeader string) *model.AppError {
-	user, err := a.Srv().Store.User().Get(userID)
+	user, err := a.Srv().Store.User().Get(context.Background(), userID)
 	if err != nil {
 		return model.NewAppError("PostUpdateChannelHeaderMessage", "api.channel.post_update_channel_header_message_and_forget.retrieve_user.error", nil, err.Error(), http.StatusBadRequest)
 	}
@@ -1526,7 +1527,7 @@ func (a *App) PostUpdateChannelHeaderMessage(userID string, channel *model.Chann
 }
 
 func (a *App) PostUpdateChannelPurposeMessage(userID string, channel *model.Channel, oldChannelPurpose string, newChannelPurpose string) *model.AppError {
-	user, err := a.Srv().Store.User().Get(userID)
+	user, err := a.Srv().Store.User().Get(context.Background(), userID)
 	if err != nil {
 		return model.NewAppError("PostUpdateChannelPurposeMessage", "app.channel.post_update_channel_purpose_message.retrieve_user.error", nil, err.Error(), http.StatusBadRequest)
 	}
@@ -1559,7 +1560,7 @@ func (a *App) PostUpdateChannelPurposeMessage(userID string, channel *model.Chan
 }
 
 func (a *App) PostUpdateChannelDisplayNameMessage(userID string, channel *model.Channel, oldChannelDisplayName, newChannelDisplayName string) *model.AppError {
-	user, err := a.Srv().Store.User().Get(userID)
+	user, err := a.Srv().Store.User().Get(context.Background(), userID)
 	if err != nil {
 		return model.NewAppError("PostUpdateChannelDisplayNameMessage", "api.channel.post_update_channel_displayname_message_and_forget.retrieve_user.error", nil, err.Error(), http.StatusBadRequest)
 	}
@@ -1905,7 +1906,7 @@ func (a *App) JoinChannel(channel *model.Channel, userID string) *model.AppError
 	userChan := make(chan store.StoreResult, 1)
 	memberChan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(userID)
+		user, err := a.Srv().Store.User().Get(context.Background(), userID)
 		userChan <- store.StoreResult{Data: user, NErr: err}
 		close(userChan)
 	}()
@@ -2014,7 +2015,7 @@ func (a *App) LeaveChannel(channelId string, userID string) *model.AppError {
 
 	uc := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(userID)
+		user, err := a.Srv().Store.User().Get(context.Background(), userID)
 		uc <- store.StoreResult{Data: user, NErr: err}
 		close(uc)
 	}()
@@ -2176,7 +2177,7 @@ func (a *App) postRemoveFromChannelMessage(removerUserId string, removedUser *mo
 }
 
 func (a *App) removeUserFromChannel(userIDToRemove string, removerUserId string, channel *model.Channel) *model.AppError {
-	user, nErr := a.Srv().Store.User().Get(userIDToRemove)
+	user, nErr := a.Srv().Store.User().Get(context.Background(), userIDToRemove)
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
 		switch {

app/channel_test.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"context"
 	"fmt"
 	"net/http"
 	"sort"
@@ -1910,7 +1911,7 @@ func TestMarkChannelsAsViewedPanic(t *testing.T) {
 
 	mockStore := th.App.Srv().Store.(*mocks.Store)
 	mockUserStore := mocks.UserStore{}
-	mockUserStore.On("Get", "userID").Return(nil, model.NewAppError("SqlUserStore.Get", "app.user.get.app_error", nil, "user_id=userID", http.StatusInternalServerError))
+	mockUserStore.On("Get", context.Background(), "userID").Return(nil, model.NewAppError("SqlUserStore.Get", "app.user.get.app_error", nil, "user_id=userID", http.StatusInternalServerError))
 	mockChannelStore := mocks.ChannelStore{}
 	mockChannelStore.On("Get", "channelID", true).Return(&model.Channel{}, nil)
 	mockChannelStore.On("GetMember", "channelID", "userID").Return(&model.ChannelMember{

app/command.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"context"
 	"errors"
 	"io"
 	"io/ioutil"
@@ -368,7 +369,7 @@ func (a *App) tryExecuteCustomCommand(args *model.CommandArgs, trigger string, m
 
 	userChan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(args.UserId)
+		user, err := a.Srv().Store.User().Get(context.Background(), args.UserId)
 		userChan <- store.StoreResult{Data: user, NErr: err}
 		close(userChan)
 	}()

app/email_batching.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"context"
 	"fmt"
 	"html/template"
 	"net/http"
@@ -194,7 +195,7 @@ func (job *EmailBatchingJob) checkPendingNotifications(now time.Time, handler fu
 }
 
 func (es *EmailService) sendBatchedEmailNotification(userID string, notifications []*batchedNotification) {
-	user, err := es.srv.Store.User().Get(userID)
+	user, err := es.srv.Store.User().Get(context.Background(), userID)
 	if err != nil {
 		mlog.Warn("Unable to find recipient for batched email notification")
 		return
@@ -205,7 +206,7 @@ func (es *EmailService) sendBatchedEmailNotification(userID string, notification
 
 	var contents string
 	for _, notification := range notifications {
-		sender, err := es.srv.Store.User().Get(notification.post.UserId)
+		sender, err := es.srv.Store.User().Get(context.Background(), notification.post.UserId)
 		if err != nil {
 			mlog.Warn("Unable to find sender of post for batched email notification")
 			continue

app/export.go

@@ -5,6 +5,7 @@ package app
 
 import (
 	"archive/zip"
+	"context"
 	"encoding/json"
 	"io"
 	"net/http"
@@ -483,7 +484,7 @@ func (a *App) BuildPostReactions(postId string) (*[]ReactionImportData, *model.A
 	}
 
 	for _, reaction := range reactions {
-		user, err := a.Srv().Store.User().Get(reaction.UserId)
+		user, err := a.Srv().Store.User().Get(context.Background(), reaction.UserId)
 		if err != nil {
 			var nfErr *store.ErrNotFound
 			if errors.As(err, &nfErr) { // this is a valid case, the user that reacted might've been deleted by now

app/integration_action.go

@@ -19,6 +19,7 @@ package app
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -84,7 +85,7 @@ func (a *App) DoPostActionWithCookie(postId, actionId, userID, selectedOption st
 
 	userChan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(upstreamRequest.UserId)
+		user, err := a.Srv().Store.User().Get(context.Background(), upstreamRequest.UserId)
 		userChan <- store.StoreResult{Data: user, NErr: err}
 		close(userChan)
 	}()

app/notification.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"context"
 	"net/http"
 	"sort"
 	"strconv"
@@ -28,7 +29,7 @@ func (a *App) SendNotifications(post *model.Post, team *model.Team, channel *mod
 
 	pchan := make(chan store.StoreResult, 1)
 	go func() {
-		props, err := a.Srv().Store.User().GetAllProfilesInChannel(channel.Id, true)
+		props, err := a.Srv().Store.User().GetAllProfilesInChannel(context.Background(), channel.Id, true)
 		pchan <- store.StoreResult{Data: props, NErr: err}
 		close(pchan)
 	}()

app/oauth.go

@@ -5,6 +5,7 @@ package app
 
 import (
 	"bytes"
+	"context"
 	b64 "encoding/base64"
 	"errors"
 	"fmt"
@@ -288,7 +289,7 @@ func (a *App) GetOAuthAccessTokenForCodeFlow(clientId, grantType, redirectUri, c
 			return nil, model.NewAppError("GetOAuthAccessToken", "api.oauth.get_access_token.redirect_uri.app_error", nil, "", http.StatusBadRequest)
 		}
 
-		user, nErr = a.Srv().Store.User().Get(authData.UserId)
+		user, nErr = a.Srv().Store.User().Get(context.Background(), authData.UserId)
 		if nErr != nil {
 			return nil, model.NewAppError("GetOAuthAccessToken", "api.oauth.get_access_token.internal_user.app_error", nil, "", http.StatusNotFound)
 		}
@@ -347,7 +348,7 @@ func (a *App) GetOAuthAccessTokenForCodeFlow(clientId, grantType, redirectUri, c
 			return nil, model.NewAppError("GetOAuthAccessToken", "api.oauth.get_access_token.refresh_token.app_error", nil, "", http.StatusNotFound)
 		}
 
-		user, nErr := a.Srv().Store.User().Get(accessData.UserId)
+		user, nErr := a.Srv().Store.User().Get(context.Background(), accessData.UserId)
 		if nErr != nil {
 			return nil, model.NewAppError("GetOAuthAccessToken", "api.oauth.get_access_token.internal_user.app_error", nil, "", http.StatusNotFound)
 		}

app/post.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -53,7 +54,7 @@ func (a *App) CreatePostAsUser(post *model.Post, currentSessionId string, setOnl
 		}
 
 		if err.Id == "api.post.create_post.town_square_read_only" {
-			user, nErr := a.Srv().Store.User().Get(post.UserId)
+			user, nErr := a.Srv().Store.User().Get(context.Background(), post.UserId)
 			if nErr != nil {
 				var nfErr *store.ErrNotFound
 				switch {
@@ -191,7 +192,7 @@ func (a *App) CreatePost(post *model.Post, channel *model.Channel, triggerWebhoo
 		}()
 	}
 
-	user, nErr := a.Srv().Store.User().Get(post.UserId)
+	user, nErr := a.Srv().Store.User().Get(context.Background(), post.UserId)
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
 		switch {

app/session.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"math"
@@ -427,7 +428,7 @@ func (a *App) SetSessionExpireInDays(session *model.Session, days int) {
 
 func (a *App) CreateUserAccessToken(token *model.UserAccessToken) (*model.UserAccessToken, *model.AppError) {
 
-	user, nErr := a.Srv().Store.User().Get(token.UserId)
+	user, nErr := a.Srv().Store.User().Get(context.Background(), token.UserId)
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
 		switch {
@@ -476,7 +477,7 @@ func (a *App) createSessionForUserAccessToken(tokenString string) (*model.Sessio
 		return nil, model.NewAppError("createSessionForUserAccessToken", "app.user_access_token.invalid_or_missing", nil, "inactive_token", http.StatusUnauthorized)
 	}
 
-	user, nErr := a.Srv().Store.User().Get(token.UserId)
+	user, nErr := a.Srv().Store.User().Get(context.Background(), token.UserId)
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
 		switch {

app/slack.go

@@ -5,6 +5,7 @@ package app
 
 import (
 	"bytes"
+	"context"
 	"fmt"
 	"mime/multipart"
 	"regexp"
@@ -88,7 +89,7 @@ func replaceUserIds(userStore store.UserStore, text string) string {
 			userIDs = append(userIDs, match[1])
 		}
 
-		if users, err := userStore.GetProfileByIds(userIDs, nil, true); err == nil {
+		if users, err := userStore.GetProfileByIds(context.Background(), userIDs, nil, true); err == nil {
 			for _, user := range users {
 				text = strings.Replace(text, "<@"+user.Id+">", "@"+user.Username, -1)
 			}

app/team.go

@@ -489,7 +489,7 @@ func (a *App) AddUserToTeam(teamID string, userID string, userRequestorId string
 
 	uchan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(userID)
+		user, err := a.Srv().Store.User().Get(context.Background(), userID)
 		uchan <- store.StoreResult{Data: user, NErr: err}
 		close(uchan)
 	}()
@@ -566,7 +566,7 @@ func (a *App) AddUserToTeamByToken(userID string, tokenID string) (*model.Team,
 
 	uchan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(userID)
+		user, err := a.Srv().Store.User().Get(context.Background(), userID)
 		uchan <- store.StoreResult{Data: user, NErr: err}
 		close(uchan)
 	}()
@@ -641,7 +641,7 @@ func (a *App) AddUserToTeamByInviteId(inviteId string, userID string) (*model.Te
 
 	uchan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(userID)
+		user, err := a.Srv().Store.User().Get(context.Background(), userID)
 		uchan <- store.StoreResult{Data: user, NErr: err}
 		close(uchan)
 	}()
@@ -1163,7 +1163,7 @@ func (a *App) RemoveUserFromTeam(teamID string, userID string, requestorId strin
 
 	uchan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(userID)
+		user, err := a.Srv().Store.User().Get(context.Background(), userID)
 		uchan <- store.StoreResult{Data: user, NErr: err}
 		close(uchan)
 	}()
@@ -1206,7 +1206,7 @@ func (a *App) RemoveTeamMemberFromTeam(teamMember *model.TeamMember, requestorId
 	message.Add("team_id", teamMember.TeamId)
 	a.Publish(message)
 
-	user, nErr := a.Srv().Store.User().Get(teamMember.UserId)
+	user, nErr := a.Srv().Store.User().Get(context.Background(), teamMember.UserId)
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
 		switch {
@@ -1368,7 +1368,7 @@ func (a *App) prepareInviteNewUsersToTeam(teamID, senderId string) (*model.User,
 
 	uchan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(senderId)
+		user, err := a.Srv().Store.User().Get(context.Background(), senderId)
 		uchan <- store.StoreResult{Data: user, NErr: err}
 		close(uchan)
 	}()
@@ -1499,7 +1499,7 @@ func (a *App) prepareInviteGuestsToChannels(teamID string, guestsInvite *model.G
 	}()
 	uchan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(senderId)
+		user, err := a.Srv().Store.User().Get(context.Background(), senderId)
 		uchan <- store.StoreResult{Data: user, NErr: err}
 		close(uchan)
 	}()

app/user.go

@@ -5,6 +5,7 @@ package app
 
 import (
 	"bytes"
+	"context"
 	b64 "encoding/base64"
 	"encoding/json"
 	"errors"
@@ -432,7 +433,7 @@ func (a *App) IsUsernameTaken(name string) bool {
 }
 
 func (a *App) GetUser(userID string) (*model.User, *model.AppError) {
-	user, err := a.Srv().Store.User().Get(userID)
+	user, err := a.Srv().Store.User().Get(context.Background(), userID)
 	if err != nil {
 		var nfErr *store.ErrNotFound
 		switch {
@@ -683,7 +684,7 @@ func (a *App) GetChannelGroupUsers(channelID string) ([]*model.User, *model.AppE
 func (a *App) GetUsersByIds(userIDs []string, options *store.UserGetByIdsOpts) ([]*model.User, *model.AppError) {
 	allowFromCache := options.ViewRestrictions == nil
 
-	users, err := a.Srv().Store.User().GetProfileByIds(userIDs, options, allowFromCache)
+	users, err := a.Srv().Store.User().GetProfileByIds(context.Background(), userIDs, options, allowFromCache)
 	if err != nil {
 		return nil, model.NewAppError("GetUsersByIds", "app.user.get_profiles.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
@@ -739,7 +740,7 @@ func (a *App) GenerateMfaSecret(userID string) (*model.MfaSecret, *model.AppErro
 }
 
 func (a *App) ActivateMfa(userID, token string) *model.AppError {
-	user, err := a.Srv().Store.User().Get(userID)
+	user, err := a.Srv().Store.User().Get(context.Background(), userID)
 	if err != nil {
 		var nfErr *store.ErrNotFound
 		switch {
@@ -1212,7 +1213,7 @@ func (a *App) sendUpdatedUserEvent(user model.User) {
 }
 
 func (a *App) UpdateUser(user *model.User, sendNotifications bool) (*model.User, *model.AppError) {
-	prev, err := a.Srv().Store.User().Get(user.Id)
+	prev, err := a.Srv().Store.User().Get(context.Background(), user.Id)
 	if err != nil {
 		var nfErr *store.ErrNotFound
 		switch {
@@ -2058,7 +2059,7 @@ func (a *App) FilterNonGroupChannelMembers(userIDs []string, channel *model.Chan
 // and returns the list of normal users present in userIDs but not in groupUsers.
 func (a *App) filterNonGroupUsers(userIDs []string, groupUsers []*model.User) ([]string, error) {
 	nonMemberIds := []string{}
-	users, err := a.Srv().Store.User().GetProfileByIds(userIDs, nil, false)
+	users, err := a.Srv().Store.User().GetProfileByIds(context.Background(), userIDs, nil, false)
 	if err != nil {
 		return nil, err
 	}
@@ -2223,19 +2224,14 @@ func (a *App) PromoteGuestToUser(user *model.User, requestorId string) *model.Ap
 // DemoteUserToGuest Convert user's roles and all his mermbership's roles from
 // regular user roles to guest roles.
 func (a *App) DemoteUserToGuest(user *model.User) *model.AppError {
-	nErr := a.Srv().Store.User().DemoteUserToGuest(user.Id)
+	demotedUser, nErr := a.Srv().Store.User().DemoteUserToGuest(user.Id)
 	a.InvalidateCacheForUser(user.Id)
 	if nErr != nil {
 		return model.NewAppError("DemoteUserToGuest", "app.user.demote_user_to_guest.user_update.app_error", nil, nErr.Error(), http.StatusInternalServerError)
 	}
 
-	demotedUser, err := a.GetUser(user.Id)
-	if err != nil {
-		mlog.Warn("Failed to get user on demote user to guest", mlog.Err(err))
-	} else {
-		a.sendUpdatedUserEvent(*demotedUser)
-		a.UpdateSessionsIsGuest(demotedUser.Id, demotedUser.IsGuest())
-	}
+	a.sendUpdatedUserEvent(*demotedUser)
+	a.UpdateSessionsIsGuest(demotedUser.Id, demotedUser.IsGuest())
 
 	teamMembers, err := a.GetTeamMembersForUser(user.Id)
 	if err != nil {
@@ -2248,6 +2244,7 @@ func (a *App) DemoteUserToGuest(user *model.User) *model.AppError {
 		channelMembers, err := a.GetChannelMembersForUser(member.TeamId, user.Id)
 		if err != nil {
 			mlog.Warn("Failed to get channel members for users on demote user to guest", mlog.Err(err))
+			continue
 		}
 
 		for _, member := range *channelMembers {
@@ -2260,7 +2257,6 @@ func (a *App) DemoteUserToGuest(user *model.User) *model.AppError {
 	}
 
 	a.ClearSessionCacheForUser(user.Id)
-
 	return nil
 }
 
@@ -2308,7 +2304,7 @@ func (a *App) GetKnownUsers(userID string) ([]string, *model.AppError) {
 
 // ConvertBotToUser converts a bot to user.
 func (a *App) ConvertBotToUser(bot *model.Bot, userPatch *model.UserPatch, sysadmin bool) (*model.User, *model.AppError) {
-	user, nErr := a.Srv().Store.User().Get(bot.UserId)
+	user, nErr := a.Srv().Store.User().Get(context.Background(), bot.UserId)
 	if nErr != nil {
 		var nfErr *store.ErrNotFound
 		switch {

app/webhook.go

@@ -4,6 +4,7 @@
 package app
 
 import (
+	"context"
 	"errors"
 	"io"
 	"net/http"
@@ -674,7 +675,7 @@ func (a *App) HandleIncomingWebhook(hookID string, req *model.IncomingWebhookReq
 
 	uchan := make(chan store.StoreResult, 1)
 	go func() {
-		user, err := a.Srv().Store.User().Get(hook.UserId)
+		user, err := a.Srv().Store.User().Get(context.Background(), hook.UserId)
 		uchan <- store.StoreResult{Data: user, NErr: err}
 		close(uchan)
 	}()