New submission from Yanyan Jiang: I am currently working on the file system reliability issues. I have a disk driver that is able to simulate crash disk sites after injected power failures. This disk is totally compatible with the Linux block driver semantics (refer to https://www.kernel.org/doc/Documentation/block/writeback_cache_control.txt), and may create many crash sites that pending blocks are partially flushed into the disk which is a common behavior of a commodity disk with write buffer.
Our automated tool confirms the corruptions could happen on a crash site at an unclean shutdown (Linux with default ext4 setting). We also found that there are some discussions on [Stackoverflow](http://stackoverflow.com/questions/4226580/prevent-python-shelve-corruption) concerning this issue. I am suggesting to explicitly remind the developers of such behaviors. Suggested documentation enhancement -------------------------------------- As a minimal database library, `shelve` does not offer as strong ACID (atomicity, consistency, isolation and durability) guarantee as a database (like SQLite). On certain system configurations, a system crash would lead to a corrupted shelve file. If you are using shelve to persistent precious data like user's document, we suggest using the following steps to ensure data is not lost: 1. Create a copy of the file, say, the temporary. 2. Operate on a copy of the temporary file. Closing a shelve db implies data to be flushed to the disk. 3. Rename the temporary file to replace the original file. Renaming is carefully treated by a journaled filesystem to be atomic. ---------- assignee: docs@python components: Documentation messages: 253188 nosy: Yanyan Jiang, docs@python priority: normal severity: normal status: open title: Shelve consistency issues type: enhancement versions: Python 2.7, Python 3.2, Python 3.3, Python 3.4, Python 3.5, Python 3.6 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue25442> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
