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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Race condition writing objects in LooseObjectDB","articleBody":"There's a TOCTTOU in LooseObjectDB when storing a new object, that causes storing an object to fail with `FileExistsError`:\r\n\r\n```\r\n   File \"patch_tree.py\", line 132, in write_tree\r\n     return self.db.store(istream).binsha\r\n   File \".venv/lib/python3.9/gitdb/db/git.py\", line 77, in store\r\n     return self._loose_db.store(istream)\r\n   File \".venv/lib/python3.9/gitdb/db/loose.py\", line 226, in store\r\n     mkdir(obj_dir)\r\nFileExistsError: [Errno 17] File exists: '/tmp/tmp.flUcclypOQ/objects/a0'\r\n```\r\n\r\n[The problem code](https://github.com/gitpython-developers/gitdb/blame/master/gitdb/db/loose.py#L225) is\r\n\r\n```python\r\n            if not isdir(obj_dir):\r\n                mkdir(obj_dir)\r\n```\r\n\r\nand what is happening is\r\n\r\n1. `isdir()` returns `False` because the directory does not exist at that moment\r\n2. The directory is created in another thread\r\n3. `mkdir()` fails with `FileExistsError`\r\n\r\nThis can be avoided by using an EAFP pattern, e.g.\r\n\r\n```python\r\nwith contextlib.suppress(FileExistsError):\r\n    mkdir(obj_dir)\r\n```","author":{"url":"https://github.com/lordmauve","@type":"Person","name":"lordmauve"},"datePublished":"2023-02-13T14:22:32.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/85/gitdb/issues/85"}