Issue #14632: Updated WatchedFileHandler to deal with race condition. Thanks to John Mulligan for the problem report and patch.
diff --git a/Lib/logging/handlers.py b/Lib/logging/handlers.py
index 0eb36f3..5af73e9 100644
--- a/Lib/logging/handlers.py
+++ b/Lib/logging/handlers.py
@@ -23,7 +23,7 @@
To use, simply 'import logging.handlers' and log away!
"""
-import logging, socket, os, cPickle, struct, time, re
+import errno, logging, socket, os, cPickle, struct, time, re
from stat import ST_DEV, ST_INO, ST_MTIME
try:
@@ -392,11 +392,13 @@
"""
def __init__(self, filename, mode='a', encoding=None, delay=0):
logging.FileHandler.__init__(self, filename, mode, encoding, delay)
- if not os.path.exists(self.baseFilename):
- self.dev, self.ino = -1, -1
- else:
- stat = os.stat(self.baseFilename)
- self.dev, self.ino = stat[ST_DEV], stat[ST_INO]
+ self.dev, self.ino = -1, -1
+ self._statstream()
+
+ def _statstream(self):
+ if self.stream:
+ sres = os.fstat(self.stream.fileno())
+ self.dev, self.ino = sres[ST_DEV], sres[ST_INO]
def emit(self, record):
"""
@@ -406,19 +408,27 @@
has, close the old stream and reopen the file to get the
current stream.
"""
- if not os.path.exists(self.baseFilename):
- stat = None
- changed = 1
- else:
- stat = os.stat(self.baseFilename)
- changed = (stat[ST_DEV] != self.dev) or (stat[ST_INO] != self.ino)
- if changed and self.stream is not None:
- self.stream.flush()
- self.stream.close()
- self.stream = self._open()
- if stat is None:
- stat = os.stat(self.baseFilename)
- self.dev, self.ino = stat[ST_DEV], stat[ST_INO]
+ # Reduce the chance of race conditions by stat'ing by path only
+ # once and then fstat'ing our new fd if we opened a new log stream.
+ # See issue #14632: Thanks to John Mulligan for the problem report
+ # and patch.
+ try:
+ # stat the file by path, checking for existence
+ sres = os.stat(self.baseFilename)
+ except OSError as err:
+ if err.errno == errno.ENOENT:
+ sres = None
+ else:
+ raise
+ # compare file system stat with that of our stream file handle
+ if not sres or sres[ST_DEV] != self.dev or sres[ST_INO] != self.ino:
+ if self.stream is not None:
+ # we have an open file handle, clean it up
+ self.stream.flush()
+ self.stream.close()
+ # open a new file handle and get new stat info from that fd
+ self.stream = self._open()
+ self._statstream()
logging.FileHandler.emit(self, record)
class SocketHandler(logging.Handler):