51 lines
1.7 KiB
Python
51 lines
1.7 KiB
Python
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#!/usr/bin/env python3
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"""Rotate only LazyBoy service logs; preserve open file descriptors (copytruncate)."""
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import fcntl
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import os
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from pathlib import Path
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import stat
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import time
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MAX_BYTES = 5 * 1024 * 1024
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BACKUPS = 3
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def rotate(root: Path, limit: int = MAX_BYTES):
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for path in root.glob('*.log'):
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try:
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fd = os.open(path, os.O_RDWR | os.O_NOFOLLOW)
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with os.fdopen(fd, 'r+b') as source:
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info = os.fstat(source.fileno())
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if not stat.S_ISREG(info.st_mode) or info.st_size <= limit:
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continue
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# Keep a bounded tail even after an unusually large burst.
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source.seek(-limit, os.SEEK_END)
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tail = source.read(limit)
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for n in range(BACKUPS - 1, 0, -1):
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previous = Path(f'{path}.{n}')
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if previous.exists() or previous.is_symlink():
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os.replace(previous, Path(f'{path}.{n + 1}'))
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backup_fd = os.open(f'{path}.1', os.O_WRONLY | os.O_CREAT | os.O_TRUNC | os.O_NOFOLLOW, 0o600)
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with os.fdopen(backup_fd, 'wb') as backup:
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backup.write(tail)
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source.truncate(0)
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except (OSError, ValueError) as error:
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print(f'log rotation skipped {path.name}: {error}', flush=True)
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def main():
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root = Path('/tmp/lazyboy')
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root.mkdir(exist_ok=True)
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with (root / 'log-rotation.lock').open('w') as lock:
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try:
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fcntl.flock(lock, fcntl.LOCK_EX | fcntl.LOCK_NB)
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except BlockingIOError:
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return
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while True:
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rotate(root)
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time.sleep(60)
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if __name__ == '__main__':
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main()
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