Enhance avatar caching by adding versioning support and improving cache read/write logic

go_cloud/cmd/api/main.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"path/filepath"
 
 	"go.b0esche.cloud/backend/internal/audit"
 	"go.b0esche.cloud/backend/internal/auth"
@@ -13,9 +14,43 @@ import (
 	"go.b0esche.cloud/backend/pkg/jwt"
 )
 
+// ensureAvatarCacheDir finds a writable, preferably persistent directory for avatar cache and updates cfg
+func ensureAvatarCacheDir(cfg *config.Config) {
+	candidates := []string{
+		cfg.AvatarCacheDir,
+		"/var/lib/b0esche/avatars",
+		"./data/avatars",
+		filepath.Join(os.TempDir(), "b0esche_avatars"),
+	}
+
+	for _, d := range candidates {
+		if d == "" {
+			continue
+		}
+		if err := os.MkdirAll(d, 0755); err == nil {
+			// Try writing a small test file to confirm write permission
+			testPath := filepath.Join(d, ".write_test")
+			if err := os.WriteFile(testPath, []byte("ok"), 0644); err == nil {
+				os.Remove(testPath)
+				if d != cfg.AvatarCacheDir {
+					fmt.Printf("[WARN] Avatar cache dir %q not usable, using %q instead. Please set AVATAR_CACHE_DIR to a persistent, writable volume.\n", cfg.AvatarCacheDir, d)
+				}
+				cfg.AvatarCacheDir = d
+				fmt.Printf("[INFO] Avatar cache directory set to %q\n", d)
+				return
+			}
+		}
+	}
+	// If none usable, keep configured value and let runtime fallback handle it
+	fmt.Printf("[WARN] No writable persistent avatar cache directory found; falling back to tmp. Set AVATAR_CACHE_DIR to a persistent path.\n")
+}
+
 func main() {
 	cfg := config.Load()
 
+	// Ensure avatar cache directory is usable and persistent when possible
+	ensureAvatarCacheDir(cfg)
+
 	dbConn, err := database.Connect(cfg)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "Database connection error: %v\n", err)