fix(avatar): use keyvalue store to cache gravatar instead of map

Resolves https://community.vikunja.io/t/docker-crash-concurrent-map-writes-google-login/3454

pkg/modules/avatar/gravatar/gravatar.go

@@ -26,37 +26,39 @@ import (
 
 	"code.vikunja.io/api/pkg/config"
 	"code.vikunja.io/api/pkg/log"
+	"code.vikunja.io/api/pkg/modules/keyvalue"
 	"code.vikunja.io/api/pkg/user"
 	"code.vikunja.io/api/pkg/utils"
 )
 
 type avatar struct {
-	content  []byte
-	mimeType string
-	loadedAt time.Time
+	Content  []byte    `json:"content"`
+	MimeType string    `json:"mime_type"`
+	LoadedAt time.Time `json:"loaded_at"`
 }
 
 // Provider is the gravatar provider
 type Provider struct {
 }
 
-// avatars is a global map which contains cached avatars of the users
-var avatars map[string]*avatar
-
-func init() {
-	avatars = make(map[string]*avatar)
-}
+const keyPrefix = "gravatar_avatar_"
 
 // GetAvatar implements getting the avatar for the user
 func (g *Provider) GetAvatar(user *user.User, size int64) ([]byte, string, error) {
 	sizeString := strconv.FormatInt(size, 10)
-	cacheKey := user.Username + "_" + sizeString
-	a, exists := avatars[cacheKey]
+	cacheKey := keyPrefix + user.Username + "_" + sizeString
+
+	var av avatar
+	exists, err := keyvalue.GetWithValue(cacheKey, &av)
+	if err != nil {
+		log.Errorf("Error retrieving gravatar from keyvalue store: %s", err)
+	}
+
 	var needsRefetch bool
 	if exists {
-		// elaped is alway < 0 so the next check would always succeed.
+		// elapsed is always < 0 so the next check would always succeed.
 		// To have it make sense, we flip that.
-		elapsed := time.Until(a.loadedAt) * -1
+		elapsed := time.Until(av.LoadedAt) * -1
 		needsRefetch = elapsed > time.Duration(config.AvatarGravaterExpiration.GetInt64())*time.Second
 		if needsRefetch {
 			log.Debugf("Refetching avatar for user %d after %v", user.ID, elapsed)
@@ -64,6 +66,7 @@ func (g *Provider) GetAvatar(user *user.User, size int64) ([]byte, string, error
 			log.Debugf("Serving avatar for user %d from cache", user.ID)
 		}
 	}
+
 	if !exists || needsRefetch {
 		log.Debugf("Gravatar for user %d with size %d not cached, requesting from gravatar...", user.ID, size)
 		req, err := http.NewRequestWithContext(context.Background(), http.MethodGet, "https://www.gravatar.com/avatar/"+utils.Md5String(strings.ToLower(user.Email))+"?s="+sizeString+"&d=mp", nil)
@@ -86,11 +89,17 @@ func (g *Provider) GetAvatar(user *user.User, size int64) ([]byte, string, error
 			mimeType = contentType
 		}
 
-		avatars[cacheKey] = &avatar{
-			content:  avatarContent,
-			mimeType: mimeType,
-			loadedAt: time.Now(),
+		av = avatar{
+			Content:  avatarContent,
+			MimeType: mimeType,
+			LoadedAt: time.Now(),
+		}
+
+		// Store in keyvalue cache
+		if err := keyvalue.Put(cacheKey, av); err != nil {
+			log.Errorf("Error storing gravatar in keyvalue store: %s", err)
 		}
 	}
-	return avatars[cacheKey].content, avatars[cacheKey].mimeType, nil
+
+	return av.Content, av.MimeType, nil
 }