merge: testing → main (reconcile 2-week divergence)

decnet/logging/inode_aware_handler.py

@@ -0,0 +1,60 @@
+"""
+RotatingFileHandler that detects external deletion or rotation.
+
+Stdlib ``RotatingFileHandler`` holds an open file descriptor for the
+lifetime of the handler.  If the target file is deleted (``rm``) or
+rotated out (``logrotate`` without ``copytruncate``), the handler keeps
+writing to the now-orphaned inode until its own size-based rotation
+finally triggers — silently losing every line in between.
+
+Stdlib ``WatchedFileHandler`` solves exactly this problem but doesn't
+rotate by size.  This subclass combines both: before each emit we stat
+the configured path and compare its inode/device to the currently open
+file; on mismatch we close and reopen.
+
+Cheap: one ``os.stat`` per log record.  Matches the pattern used by
+``decnet/collector/worker.py:_reopen_if_needed``.
+"""
+from __future__ import annotations
+
+import logging
+import logging.handlers
+import os
+
+
+class InodeAwareRotatingFileHandler(logging.handlers.RotatingFileHandler):
+    """RotatingFileHandler that reopens the target on external rotation/deletion."""
+
+    def _should_reopen(self) -> bool:
+        if self.stream is None:
+            return True
+        try:
+            disk_stat = os.stat(self.baseFilename)
+        except FileNotFoundError:
+            return True
+        except OSError:
+            return False
+        try:
+            open_stat = os.fstat(self.stream.fileno())
+        except OSError:
+            return True
+        return (disk_stat.st_ino != open_stat.st_ino
+                or disk_stat.st_dev != open_stat.st_dev)
+
+    def emit(self, record: logging.LogRecord) -> None:
+        if self._should_reopen():
+            try:
+                if self.stream is not None:
+                    self.close()
+            except Exception:  # nosec B110
+                pass
+            try:
+                self.stream = self._open()
+            except OSError:
+                # A logging handler MUST NOT crash its caller. If we can't
+                # reopen (e.g. file is root-owned after `sudo decnet deploy`
+                # and the current process is non-root), defer to the stdlib
+                # error path, which just prints a traceback to stderr.
+                self.handleError(record)
+                return
+        super().emit(record)