WIP Gc scheduler taskstate #6246
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fjetter
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Apr 29, 2022
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| # _workers = self.workers | ||
| # _events = self.events | ||
| # def remove_worker_from_events(): | ||
| # # If the worker isn't registered anymore after the delay, remove from events | ||
| # if address not in _workers and address in _events: | ||
| # del _events[address] | ||
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| # cleanup_delay = parse_timedelta( | ||
| # dask.config.get("distributed.scheduler.events-cleanup-delay") | ||
| # ) | ||
| # self.loop.call_later(cleanup_delay, remove_worker_from_events) | ||
| # logger.debug("Removed worker %s", ws) |
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tornado call_later, add_callback, etc. things keep a reference around. With the above construction, we can break references to the scheduler but the sets/dicts still include references to WorkerState instances which themselves hold references to TaskState objects.
| """ | ||
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| def __init__(self, scheduler): | ||
| self.scheduler = scheduler |
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this is obvious but the GC should be able to break this cycle
distributed/scheduler.py
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| resources = {} | ||
| aliases = {} | ||
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| self._task_state_collections = [unrunnable] |
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This construction feels a bit off and is a relict of Cython. I will come back to this again once we removed the SchedulerState
This was referenced Apr 29, 2022
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I tried introducing a weakref instance check for the TaskState objects as proposed in #6226 (comment)
but I failed because they are actually never GCed.
It is not surprising that our classes are highly interconnected things and I am not at all surprised that we explicitly need to collect but the cycle detection doesn't suffice to release these objects. Turns out, we're leaking a bunch of explicit references all over the place.
Some of these are not obvious and I figured this bit of effort I invested here is worth preserving. I'll comment in-code for a few (to me) surprising things