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):
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index 2aac360..701e5ab 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -31,6 +31,7 @@
import gc
import json
import os
+import random
import re
import select
import socket
@@ -40,6 +41,7 @@
import tempfile
from test.test_support import captured_stdout, run_with_locale, run_unittest
import textwrap
+import time
import unittest
import warnings
import weakref
@@ -1873,6 +1875,43 @@
self.assertTrue(c2 is c3)
+class HandlerTest(BaseTest):
+
+ @unittest.skipUnless(threading, 'Threading required for this test.')
+ def test_race(self):
+ # Issue #14632 refers.
+ def remove_loop(fname, tries):
+ for _ in range(tries):
+ try:
+ os.unlink(fname)
+ except OSError:
+ pass
+ time.sleep(0.004 * random.randint(0, 4))
+
+ def cleanup(remover, fn, handler):
+ handler.close()
+ remover.join()
+ if os.path.exists(fn):
+ os.unlink(fn)
+
+ fd, fn = tempfile.mkstemp('.log', 'test_logging-3-')
+ os.close(fd)
+ del_count = 1000
+ log_count = 1000
+ remover = threading.Thread(target=remove_loop, args=(fn, del_count))
+ remover.daemon = True
+ remover.start()
+ for delay in (False, True):
+ h = logging.handlers.WatchedFileHandler(fn, delay=delay)
+ self.addCleanup(cleanup, remover, fn, h)
+ f = logging.Formatter('%(asctime)s: %(levelname)s: %(message)s')
+ h.setFormatter(f)
+ for _ in range(log_count):
+ time.sleep(0.005)
+ r = logging.makeLogRecord({'msg': 'testing' })
+ h.handle(r)
+
+
# Set the locale to the platform-dependent default. I have no idea
# why the test does this, but in any case we save the current locale
# first and restore it at the end.
@@ -1882,7 +1921,7 @@
CustomLevelsAndFiltersTest, MemoryHandlerTest,
ConfigFileTest, SocketHandlerTest, MemoryTest,
EncodingTest, WarningsTest, ConfigDictTest, ManagerTest,
- ChildLoggerTest)
+ ChildLoggerTest, HandlerTest)
if __name__ == "__main__":
test_main()