mirror of https://github.com/python/cpython
bpo-42160: tempfile: Reduce overhead of pid check. (GH-22997)
The _RandomSequence class in tempfile used to check the current pid every time its rng property was used. This commit replaces this code with `os.register_at_fork` to reduce the overhead.
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@ -129,24 +129,22 @@ class _RandomNameSequence:
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_RandomNameSequence is an iterator."""
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characters = "abcdefghijklmnopqrstuvwxyz0123456789_"
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@property
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def rng(self):
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cur_pid = _os.getpid()
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if cur_pid != getattr(self, '_rng_pid', None):
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self._rng = _Random()
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self._rng_pid = cur_pid
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return self._rng
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def __init__(self, characters="abcdefghijklmnopqrstuvwxyz0123456789_", length=8, rng=None):
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if rng is None:
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rng = _Random()
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if hasattr(_os, "fork"):
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# prevent same state after fork
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_os.register_at_fork(after_in_child=rng.seed)
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self.rng = rng
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self.characters = characters
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self.length = length
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def __iter__(self):
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return self
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def __next__(self):
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c = self.characters
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choose = self.rng.choice
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letters = [choose(c) for dummy in range(8)]
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return ''.join(letters)
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return ''.join(self.rng.choices(c, k=self.length))
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def _candidate_tempdir_list():
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"""Generate a list of candidate temporary directories which
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@ -153,8 +153,8 @@ class TestRandomNameSequence(BaseTestCase):
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self.r = tempfile._RandomNameSequence()
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super().setUp()
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def test_get_six_char_str(self):
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# _RandomNameSequence returns a six-character string
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def test_get_eight_char_str(self):
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# _RandomNameSequence returns a eight-character string
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s = next(self.r)
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self.nameCheck(s, '', '', '')
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@ -0,0 +1 @@
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Replaced pid check in ``tempfile._RandomNameSequence`` with ``os.register_at_fork`` to reduce overhead.
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