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Description:

perpetuo 0.5.1

Perpetuo

perpetuo, verb: To cause to continue uninterruptedly, to proceed with
continually

Perpetuo is a stall tracker for Python. Specifically, it can detect when:

One thread is holding the GIL for too long, blocking other threads from having
a chance to run (requires an instrumented version of CPython)

One Trio task is running too long without checkpointing, blocking other tasks
from having a chance to run

The actual monitoring is done from a separate process, using a customized
version of py-spy. So the monitoring is
very low overhead and should not interfere with the monitored process at all.
The goal is to be able to use this in production.
Quickstart

pip install perpetuo

Optional: patch CPython (see below)

import perpetuo

If you're using Trio: call perpetuo.dwim() inside trio.run
If you're not using Trio: call perpetuo.dwim() anywhere

Optional: log perpetuo.dwim()'s return value to see what it did

Available API
perpetuo.start_watcher(): Spawns the monitoring process in the background.
perpetuo.instrument_gil(): Enables GIL instrumentation, or raises
RuntimeError if you don't have the patched version of CPython.
perpetuo.instrument_trio(): Enables Trio instrumentation. Must be called
inside trio.run.
perpetuo.dwim(): Attempts to call all the above functions as appropriate, and
returns a list of strings describing which operations it actually performed. If
you're using Trio, make sure to call it inside trio.run.
StallTracker: Low-level class that allows you to add custom instrumentation to
other things. See source for details.
Patching CPython to instrument the GIL
Currently the patch is only available for CPython version 3.10.*. It can be
downloaded here:
https://github.com/python/cpython/compare/3.10...njsmith:cpython:njs/perpetuo-gil.diff
Bonus
Niccolò Paganini's Moto Perpetuo, performed by Antal Zalai