Fix memory leak during successful CSV rendering

- Delay return until Context Manager `with open()`
  has finished and force GC in between.
- Explicitly `del` data, reader, sheets when they
  are on longer used.

Author: cslzchen

mfr/extensions/tabular/libs/stdlib_tools.py

@@ -20,6 +20,7 @@ def csv_stdlib(fp):
     else:
         _set_dialect_quote_attrs(dialect, data)
 
+    del data
     reader = csv.DictReader(fp, dialect=dialect)
     columns = []
     # update the reader field names to avoid duplicate column names when performing row extraction
@@ -53,6 +54,7 @@ def csv_stdlib(fp):
     if not columns and not rows:
         raise EmptyTableError('Table empty or corrupt.', extension='csv')
 
+    del reader
     return {'Sheet 1': (columns, rows)}
 
 

mfr/extensions/tabular/render.py

@@ -32,16 +32,20 @@ def render(self):
 
         with open(self.file_path, errors='replace') as fp:
             sheets, size, nbr_rows, nbr_cols = self._render_grid(fp, self.metadata.ext)
-            # gc.collect()
-            if sheets and size:
-                return self.TEMPLATE.render(
-                    base=self.assets_url,
-                    width=settings.TABLE_WIDTH,
-                    height=settings.TABLE_HEIGHT,
-                    sheets=json.dumps(sheets),
-                    options=json.dumps(size),
-                )
-        # gc.collect()
+
+        # Force GC
+        gc.collect()
+
+        if sheets and size:
+            return self.TEMPLATE.render(
+                base=self.assets_url,
+                width=settings.TABLE_WIDTH,
+                height=settings.TABLE_HEIGHT,
+                sheets=json.dumps(sheets),
+                options=json.dumps(size),
+            )
+
+        assert nbr_rows and nbr_cols
         raise exceptions.TableTooBigError(
             'Table is too large to render.',
             extension=self.metadata.ext,
@@ -93,6 +97,7 @@ def _render_grid(self, fp, ext, *args, **kwargs):
                 break
 
         if table_too_big:
+            del sheets
             return None, None, nbr_rows, nbr_cols
 
         return sheets, size, None, None