mirror of https://github.com/scrapy/scrapy.git
83 lines
2.6 KiB
Python
83 lines
2.6 KiB
Python
"""This module provides some functions and classes to record and report
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references to live object instances.
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If you want live objects for a particular class to be tracked, you only have to
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subclass from object_ref (instead of object).
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About performance: This library has a minimal performance impact when enabled,
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and no performance penalty at all when disabled (as object_ref becomes just an
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alias to object in that case).
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.. note:: PyPy uses a tracing garbage collector, so objects may
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remain in the ``live_refs`` longer than expected, even after they
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go out of scope. If deterministic behavior is required, you may need
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to explicitly trigger garbage collection or call ``trackref.live_refs.clear()``.
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"""
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from __future__ import annotations
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from collections import defaultdict
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from operator import itemgetter
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from time import monotonic_ns
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from types import NoneType
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from typing import TYPE_CHECKING, Any
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from weakref import WeakKeyDictionary
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if TYPE_CHECKING:
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from collections.abc import Iterable
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# typing.Self requires Python 3.11
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from typing_extensions import Self
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live_refs: defaultdict[type, WeakKeyDictionary] = defaultdict(WeakKeyDictionary)
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class object_ref:
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"""Inherit from this class to a keep a record of live instances"""
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__slots__ = ()
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def __new__(cls, *args: Any, **kwargs: Any) -> Self:
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obj = object.__new__(cls)
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live_refs[cls][obj] = monotonic_ns()
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return obj
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# using Any as it's hard to type type(None)
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def format_live_refs(ignore: Any = NoneType) -> str:
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"""Return a tabular representation of tracked objects"""
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s = "Live References\n\n"
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now_ns = monotonic_ns()
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for cls, wdict in sorted(live_refs.items(), key=lambda x: x[0].__name__):
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if not wdict:
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continue
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if issubclass(cls, ignore):
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continue
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oldest_ns = min(wdict.values())
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s += f"{cls.__name__:<30} {len(wdict):6} oldest: {int((now_ns - oldest_ns) // 1e9)}s ago\n"
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return s
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def print_live_refs(*a: Any, **kw: Any) -> None:
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"""Print tracked objects"""
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print(format_live_refs(*a, **kw))
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def get_oldest(class_name: str) -> Any:
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"""Get the oldest object for a specific class name"""
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for cls, wdict in live_refs.items():
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if cls.__name__ == class_name:
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if not wdict:
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break
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return min(wdict.items(), key=itemgetter(1))[0]
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return None
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def iter_all(class_name: str) -> Iterable[Any]:
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"""Iterate over all objects of the same class by its class name"""
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for cls, wdict in live_refs.items():
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if cls.__name__ == class_name:
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return wdict.keys()
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return ()
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