PYTHON-5418 Support subinterpreters and InterpreterPoolExecutor by blink1073 · Pull Request #31 · blink1073/mongo-python-driver

blink1073 · 2026-09-21T22:13:13Z

PYTHON-5418

Changes in this PR

PeriodicExecutor starts non-daemon threads in subinterpreters, where daemon threads are disallowed. The monitor shutdown handler is registered with threading._register_atexit (only in those interpreters) so executors are stopped and joined at interpreter teardown; main-interpreter shutdown ordering is unchanged.
Added tests for PeriodicExecutor in a subinterpreter and a dedicated test_subinterpreters.py‎ covering direct subinterpeter and InterpreterPoolExecutor usage with sync and aync clients.
Note: an interpreter may block on teardown until in-flight monitor work completes.
Almost all of the changes are new tests.

Test Plan

The new subinterpreter tests pass on Python 3.14 and 3.15.
With the shutdown changes reverted, test_subinterpreters fails, demonstrating regression coverage.

Checklist

Checklist for Author

Did you update the changelog (if necessary)?
Is there test coverage?
Is any followup work tracked in a JIRA ticket? If so, add link(s).

Checklist for Reviewer

Does the title of the PR reference a JIRA Ticket?
Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
Is all relevant documentation (README or docstring) updated?

PeriodicExecutor now falls back to a non-daemon thread when daemon threads are disallowed (subinterpreters). The monitor shutdown handler is also registered with threading._register_atexit so executors are stopped and joined before interpreter teardown. Adds regression tests for PeriodicExecutor in a real subinterpreter and for concurrent MongoClients across subinterpreters (Python 3.14+).

Runs live MongoClients inside interpreters managed by the standard InterpreterPoolExecutor, mirroring the existing multi-threaded checks. The pool's interpreters do not allow daemon threads, so this exercises the non-daemon monitor thread fallback and its shutdown handling.

The worker interpreters may not have the repo root on sys.path (the stdlib test package shadows the repo's), so the pickled worker function failed to unpickle. Submit the builtin exec with a code string that inserts the main interpreter's sys.path before importing pymongo.

Runs live AsyncMongoClients inside interpreters managed by InterpreterPoolExecutor. The async client runs its background tasks on the interpreter's own event loop rather than in threads, covering the other shutdown path.

Invert the is_running guard in test_subinterpreters: closing an idle interpreter runs threading._shutdown, which stops and joins pymongo's monitor threads, so the successful path must close them. Note in the changelog that both clients are covered by the subinterpreter tests.

Only register the monitor shutdown handler with threading._register_atexit when the interpreter disallows daemon threads, preserving normal main interpreter shutdown ordering.

Test AsyncPeriodicExecutor in a subinterpreter in the async suite, tighten the code comments, and note that both clients are supported in the changelog.

Add test/asynchronous/test_subinterpreters.py with the subinterpreter and InterpreterPoolExecutor client tests, written once in async style and mirrored by synchro. Remove them from test_threads.py, which is not mirrored. Collapse the periodic executor test's duplicated worker blocks into one block and make its async target a coroutine.

Commit 623ecb0 tightened the comment in the async monitor but did not regenerate the sync mirror.

…preter The sync worker blocks on an event set by the target's first run, so the interpreter is destroyed with the monitor live in its interval loop. The async worker yields to its loop once, which runs the monitor task's first step.

blink1073 added 7 commits September 21, 2026 16:50

PYTHON-5418 Note subinterpreter support in the changelog

c6b1d57

PYTHON-5418 Test the async client in subinterpreters

5e1109c

Runs live AsyncMongoClients inside interpreters managed by InterpreterPoolExecutor. The async client runs its background tasks on the interpreter's own event loop rather than in threads, covering the other shutdown path.

PYTHON-5418 Limit the early shutdown registration to subinterpreters

79611c2

Only register the monitor shutdown handler with threading._register_atexit when the interpreter disallows daemon threads, preserving normal main interpreter shutdown ordering.