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64 lines
2.3 KiB
Python
64 lines
2.3 KiB
Python
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"""
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Helpers for managing garbage collection.
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:ivar fileDescriptorResource: A garbage-collection-informing resource tracker
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for file descriptors. This is used to trigger a garbage collection when
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it may be possible to reclaim a significant number of file descriptors as
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a result. Register allocation and release of *bare* file descriptors with
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this object (file objects, socket objects, etc, have their own integration
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with the garbage collector and don't need to bother with this).
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"""
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__all__ = [
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"fileDescriptorResource",
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]
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import gc
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import attr
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@attr.s
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class _ResourceTracker(object):
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"""
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Keep track of some kind of resource and trigger a full garbage collection
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when allocations outnumber releases by some amount.
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:ivar int _counter: The number of allocations that have happened in excess
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of releases since the last full collection triggered by this tracker.
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:ivar int _threshold: The number of excess allocations at which point a
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full collection will be triggered.
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"""
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_counter = attr.ib(default=0)
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_threshold = attr.ib(default=25)
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def allocate(self):
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"""
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Register the allocation of an instance of this resource.
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"""
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self._counter += 1
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if self._counter > self._threshold:
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gc.collect()
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# Garbage collection of this resource has done what it can do. If
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# nothing was collected, it doesn't make any sense to trigger
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# another full collection the very next time the resource is
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# allocated. Start the counter over again. The next collection
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# happens when we again exceed the threshold.
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self._counter = 0
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def release(self):
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"""
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Register the release of an instance of this resource.
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"""
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if self._counter > 0:
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# If there were any excess allocations at this point, account for
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# there now being one fewer. It is not helpful to allow the
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# counter to go below zero (as naturally would if a collection is
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# triggered and then subsequently resources are released). In
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# that case, we would be operating as if we had set a higher
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# threshold and that is not desired.
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self._counter -= 1
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fileDescriptorResource = _ResourceTracker()
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