import os
import threading

from logging.handlers import WatchedFileHandler
import logging

handler = WatchedFileHandler('foo')

record = logging.LogRecord('foo', logging.WARN, 'foo', 25, 'foo', None, None)

def write():
    handler.emit(record)

os.unlink('foo')
a = threading.Thread(target=write)
b = threading.Thread(target=write)
a.start()
b.start()
a.join()
b.join()

handler.emit(record)