48 lines
1.4 KiB
Python
48 lines
1.4 KiB
Python
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# Copyright The OpenTelemetry Authors
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from threading import Lock
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from typing import Callable
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class Once:
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"""Execute a function exactly once and block all callers until the function returns
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Same as golang's `sync.Once <https://pkg.go.dev/sync#Once>`_
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"""
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def __init__(self) -> None:
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self._lock = Lock()
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self._done = False
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def do_once(self, func: Callable[[], None]) -> bool:
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"""Execute ``func`` if it hasn't been executed or return.
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Will block until ``func`` has been called by one thread.
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Returns:
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Whether or not ``func`` was executed in this call
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"""
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# fast path, try to avoid locking
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if self._done:
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return False
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with self._lock:
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if not self._done:
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func()
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self._done = True
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return True
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return False
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