mirror of
https://github.com/Shu-Ying/farm_service.git
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51 lines
1.8 KiB
Python
51 lines
1.8 KiB
Python
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"""Serialize publishers for one output; process exit releases OS locks."""
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from contextlib import contextmanager
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import errno
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import os
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import threading
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import time
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_LOCKS = {}
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_REGISTRY_GUARD = threading.Lock()
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@contextmanager
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def publication_lock(output):
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key = os.path.normcase(str(output.resolve()))
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with _REGISTRY_GUARD:
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local = _LOCKS.setdefault(key, threading.Lock())
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# Some OS record locks are process-scoped, so threads also need a mutex.
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with local:
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output.mkdir(parents=True, exist_ok=True)
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# Keep this inode/path permanently: unlinking it could split waiters
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# between different locks. It contains no publication state or secrets.
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with (output / ".publish.lock").open("a+b") as stream:
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if os.name == "nt":
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import msvcrt
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if os.fstat(stream.fileno()).st_size == 0:
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stream.write(b"\0")
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stream.flush()
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stream.seek(0)
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while True:
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try:
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msvcrt.locking(stream.fileno(), msvcrt.LK_NBLCK, 1)
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break
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except OSError as error:
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if error.errno not in (errno.EACCES, errno.EAGAIN,
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errno.EDEADLK):
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raise
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time.sleep(0.05)
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try:
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yield
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finally:
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stream.seek(0)
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msvcrt.locking(stream.fileno(), msvcrt.LK_UNLCK, 1)
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else:
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import fcntl
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fcntl.flock(stream.fileno(), fcntl.LOCK_EX)
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try:
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yield
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finally:
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fcntl.flock(stream.fileno(), fcntl.LOCK_UN)
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