61 lines
2.2 KiB
Python
61 lines
2.2 KiB
Python
"""
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RotatingFileHandler that detects external deletion or rotation.
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Stdlib ``RotatingFileHandler`` holds an open file descriptor for the
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lifetime of the handler. If the target file is deleted (``rm``) or
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rotated out (``logrotate`` without ``copytruncate``), the handler keeps
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writing to the now-orphaned inode until its own size-based rotation
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finally triggers — silently losing every line in between.
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Stdlib ``WatchedFileHandler`` solves exactly this problem but doesn't
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rotate by size. This subclass combines both: before each emit we stat
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the configured path and compare its inode/device to the currently open
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file; on mismatch we close and reopen.
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Cheap: one ``os.stat`` per log record. Matches the pattern used by
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``decnet/collector/worker.py:_reopen_if_needed``.
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"""
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from __future__ import annotations
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import logging
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import logging.handlers
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import os
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class InodeAwareRotatingFileHandler(logging.handlers.RotatingFileHandler):
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"""RotatingFileHandler that reopens the target on external rotation/deletion."""
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def _should_reopen(self) -> bool:
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if self.stream is None:
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return True
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try:
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disk_stat = os.stat(self.baseFilename)
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except FileNotFoundError:
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return True
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except OSError:
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return False
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try:
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open_stat = os.fstat(self.stream.fileno())
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except OSError:
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return True
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return (disk_stat.st_ino != open_stat.st_ino
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or disk_stat.st_dev != open_stat.st_dev)
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def emit(self, record: logging.LogRecord) -> None:
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if self._should_reopen():
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try:
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if self.stream is not None:
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self.close()
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except Exception: # nosec B110
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pass
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try:
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self.stream = self._open()
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except OSError:
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# A logging handler MUST NOT crash its caller. If we can't
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# reopen (e.g. file is root-owned after `sudo decnet deploy`
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# and the current process is non-root), defer to the stdlib
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# error path, which just prints a traceback to stderr.
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self.handleError(record)
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return
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super().emit(record)
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