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gevent v21.1.0 Release Notes

Release Date: 2021-01-15 // over 3 years ago

  • 🛠 Bugfixes

    • 👉 Make gevent FileObjects more closely match the semantics of native file objects for the name attribute:

      • Objects opened from a file descriptor integer have that integer as their name. (Note that this is the Python 3 semantics; Python 2 native file objects returned from os.fdopen() have the string "" as their name , but here gevent always follows Python 3.)
      • The name remains accessible after the file object is closed.

    Thanks to Dan Milon. See :issue:1745.

    Misc

    ⚠ Make gevent.event.AsyncResult print a warning when it detects improper cross-thread usage instead of hanging.

    AsyncResult has never been safe to use from multiple threads. It, like most gevent objects, is intended to work with greenlets from a single thread. Using AsyncResult from multiple threads has undefined semantics. The safest way to communicate between threads is using an event loop async watcher.

    Those undefined semantics changed in recent gevent versions, making it more likely that an abused AsyncResult would misbehave in ways that could cause the program to hang.

    Now, when AsyncResult detects a situation that would hang, it ⚠ prints a warning to stderr. Note that this is best-effort, and hangs are still possible, especially under PyPy 7.3.3.

    At the same time, AsyncResult is tuned to behave more like it did in older versions, meaning that the hang is once again much less likely. If you were getting lucky and using AsyncResult ⏪ successfully across threads, this may restore your luck. In addition, cross-thread wakeups are faster. Note that the gevent hub now uses an extra file descriptor to implement this.

    👀 Similar changes apply to gevent.event.Event (see :issue:1735).

    👀 See :issue:1739.