Revert "Remove friends map mutex because map access won't occur concu…

…rrently"

This reverts commit 94a0dc2.

pkg/service/service.go

@@ -77,6 +77,7 @@ type DBListRepo struct {
 
 	email                     string
 	friends                   map[string]map[string]int64
+	friendsMapLock            sync.Mutex
 	friendsMostRecentChangeDT int64
 	friendsLastPushDT         int64
 
@@ -125,7 +126,8 @@ func NewDBListRepo(localWalFile LocalWalFile, webTokenStore WebTokenStore, syncF
 		processedPartialWals:     make(map[string]struct{}),
 		processedPartialWalsLock: &sync.Mutex{},
 
-		friends: make(map[string]map[string]int64),
+		friends:        make(map[string]map[string]int64),
+		friendsMapLock: sync.Mutex{},
 	}
 
 	// The localWalFile gets attached to the Wal independently (there are certain operations

pkg/service/wal.go

@@ -362,6 +362,8 @@ func (r *DBListRepo) generateFriendChangeEvents(e EventLog, item *ListItem) {
 		var friendItems map[string]int64
 		var friendExists bool
 		func() {
+			r.friendsMapLock.Lock()
+			defer r.friendsMapLock.Unlock()
 			if friendItems, friendExists = r.friends[email]; !friendExists {
 				friendItems = make(map[string]int64)
 				r.friends[email] = friendItems
@@ -388,6 +390,8 @@ func (r *DBListRepo) generateFriendChangeEvents(e EventLog, item *ListItem) {
 		if friendItems, friendExists := r.friends[email]; friendExists {
 			if dtLastChange, exists := friendItems[key]; exists && e.UnixNanoTime > dtLastChange {
 				func() {
+					r.friendsMapLock.Lock()
+					defer r.friendsMapLock.Unlock()
 					delete(r.friends[email], key)
 					if len(r.friends[email]) == 0 {
 						delete(r.friends, email)
@@ -961,7 +965,8 @@ func checkWalIntegrity(wal *[]EventLog) (*ListItem, []*ListItem, error) {
 		allWalFileMut:  &sync.RWMutex{},
 		syncWalFileMut: &sync.RWMutex{},
 
-		friends: make(map[string]map[string]int64),
+		friends:        make(map[string]map[string]int64),
+		friendsMapLock: sync.Mutex{},
 	}
 
 	// Use the Replay function to generate the linked lists