News and Updates

SQLAlchemy 2.0.55 is now available.

Release 2.0.55 contains a series of bugfixes backported from the 2.1.x series. Of particular note are many fixes involving correct handling of asyncio task cancellation with active database connections as well as garbage collection surrounding connections (particularly asyncio connections) and cursors.

Task-cancellation and garbage collection issues that were previously difficult or impossible to reproduce are now being reported by users at a dramatically higher rate. There are two factors at play in this change. One is that while Python asyncio programming is typically straightforward when dealing with IO streams and await keywords, the presence of the task.cancel() and CancelledError constructs adds a deeply complex layer to asyncio applications, turning every await into a potential source of an exception that requires context-specific cleanup of all resources and proper re-propagation when it occurs. The other is that these issues were previously very difficult to report as they are transient and often nearly impossible to reproduce, and when they were reported we were often unable to reproduce them. However, with the advent of large language models, users can now isolate report these issues with accurate reproduction cases, allowing them to be fixed.

As a result of these new capabilities, SQLAlchemy's internal testing now makes use of a test harness that exercises a task.cancel() scenario at every await along an entire chain of operations, ensuring that for each one, database connections are not "leaked" whether or not they are marked as invalid, and the original CancelledError is correctly propagated.

The detailed changelog for 2.0.55 is at Changelog.

SQLAlchemy 2.0.55 is available on the Download Page.