Add media folder size to admin template

gallery/cache.py

@@ -7,3 +7,20 @@ def cached_or_set(key, timeout, func):
         value = func()
         cache.set(key, value, timeout)
     return value
+
+
+def cached_or_set_locked(key, timeout, func):
+    value = cache.get(key)
+    if value is None:
+        if cache.add(f"{key}:lock", True, 30):  # 30s lukko
+            value = func()
+            cache.set(key, value, timeout)
+            cache.delete(f"{key}:lock")
+        else:
+            import time
+            for _ in range(10):  # max 1s odotus
+                value = cache.get(key)
+                if value is not None:
+                    break
+                time.sleep(0.1)
+    return value