Why doesn't my TimedRotatingFileHandler rotate at midnight?

This is my config file:

[loggers]
keys=root

[handlers]
keys=TimedRotatingFileHandler

[formatters]
keys=simpleFormatter

[logger_root]
level=DEBUG
handlers=TimedRotatingFileHandler

[handler_TimedRot开发者_StackOverflowatingFileHandler]
class=handlers.TimedRotatingFileHandler
level=DEBUG
formatter=simpleFormatter
args=('driver.log', 'midnight', 1, 30)

[formatter_simpleFormatter]
format=%(asctime)s - %(name)s - %(levelname)s - %(message)s
datefmt=

In my code I setup and use the logger like this:

import logging
import logging.config

logging.config.fileConfig('logging.conf')
logging.info('Some message...')

Messages are logged to the file I specify (driver.log), but the rotations at midnight never happen.

Must the process be running at midnight for the rotation to occur? This is a batch process that I run every 15 minutes and it is never actually running at midnight.

The answer is that the process must be running all the time for this to work properly.

From http://bytes.com/topic/python/answers/595931-timedrotatingfilehandler-isnt-rotating-midnight:

Rotating should happen when the logging process creates the handler before midnight and makes a logging call destined for that handler after midnight.

I would guess this really only happens when the process is running at midnight. In your case (cronjob not running very long), you should go with a simple log file, where the current date is added to the logfilename. This way, a "rollover" happens automatically.

I have also run into this problem, for various reasons I couldn't use rotatelog and a cron to rotate logs is just adding an extra thing that might go wrong. I used the function below to rotate the files, on a daily basis.

import os
import datetime
import glob

def sort_number_ext(s):
    try:
        return int(os.path.splitext(s)[1][1:])
    except:
        return s

def rotate_file(file, keep=30):
    """ Rotate a file if needed. If the file wasn't modified today then we
    rotate it around and remove old files """

    modified_date = datetime.datetime.fromtimestamp(os.path.getmtime(file))

    if modified_date.date() == datetime.datetime.today().date():
        return False

    old_files = glob.glob(file + ".*")
    old_files.sort(key=sort_number_ext, reverse=True)

    for f in old_files:
        try:
            number = int(os.path.splitext(f)[1][1:])
        except ValueError:
            continue

        if number >= keep:
            # If at or above keep limit, remove.
            os.unlink(f)
        else:
            # Increment.
            new = "%s.%s" % (os.path.splitext(f)[0], number + 1)
            os.rename(f, new)

    # Finally rename our log.
    os.rename(file, "%s.1" % file)
    return True

I call this to rotate my logs before initializing the logger.