Use DF for disk sizes

src/collectors/container_collector.py

@@ -241,23 +241,28 @@ class ContainerCollector(BaseCollector):
     
     def _get_container_disk_usage(self, container) -> int:
         """
-        Get the disk usage for a container in bytes.
-        This includes the writable layer size (SizeRw) and root filesystem size (SizeRootFs).
+        Get the disk usage for a container in bytes using the Docker system df API.
+        This provides accurate size information including writable layer and virtual size.
         """
         try:
-            # Reload container to get latest attributes with size information
-            container.reload()
-            attrs = container.attrs
+            # Use the system df API to get accurate container size information
+            # This is more reliable than container.attrs which often doesn't include size data
+            df_data = self.client.df()
+            containers_info = df_data.get('Containers', [])
             
-            # SizeRw: Size of files that have been created or changed
-            size_rw = attrs.get('SizeRw', 0)
+            # Find the matching container by ID
+            for container_info in containers_info:
+                if container_info.get('Id', '').startswith(container.id):
+                    # SizeRw: Size of files created or changed in the writable layer
+                    size_rw = container_info.get('SizeRw', 0)
+                    # SizeRootFs: Total size including all layers (image + writable)
+                    size_rootfs = container_info.get('SizeRootFs', 0)
+                    
+                    # Return SizeRootFs (total size) if available, otherwise SizeRw
+                    return size_rootfs if size_rootfs > 0 else size_rw
             
-            # SizeRootFs: Total size of container filesystem (read-only + writable layers)
-            size_rootfs = attrs.get('SizeRootFs', 0)
-            
-            # Return the total size (SizeRootFs includes SizeRw)
-            # If SizeRootFs is not available, fall back to SizeRw
-            return size_rootfs if size_rootfs > 0 else size_rw
+            # Container not found in df data
+            return 0
             
         except Exception as e:
             print(f"Warning: Error getting disk usage: {e}")