Does not works in Python 2.7 (Windows)

[q88798]

The following code from the simple example simply hang:-

from logging import getLogger, INFO
from cloghandler import ConcurrentRotatingFileHandler
import os

log = getLogger()
# Use an absolute path to prevent file rotation trouble.
logfile = os.path.abspath("mylogfile.log")
# Rotate log after reaching 512K, keep 5 old copies.
rotateHandler = ConcurrentRotatingFileHandler(logfile, "a", 512*1024, 5)
log.addHandler(rotateHandler)
log.setLevel(INFO)

log.info("Here is a very exciting log message, just for you") # <-- hang over here

Environment:-
Windows 7
Python 2.7.5 (32-bit)
ConcurrentLogHandler-0.9.1

[Hemie143 (hemie143)]

Doesn't work in Python 3.4 either.
The log entries aren't flushed and/or it stucks the python script. Probably something isn't released properly.

Are there chances that this will ever be corrected ?

[Preston Landers (planders)]

The problem is in how the Python logging package acquires locks recursively when it already holds a lock. With the base class's threading lock this is already handled.

I've got a git fork which fixes the problem here:

https://github.com/Preston-Landers/ConcurrentLogHandler

Tested with Python 3.6.0b4 x64 on Windows 10.

The problem is that logging.Handler calls acquire() to emit the message and then calls flush(), which also calls acquire() while the lock is already held, and this causes a deadlock given the locking technique used.

The fix in cloghandler.py is to keep track of the number of recursive acquires() and only do the actual locking or releasing when the stack is size 1.