Need to do a daily log rotation (0utc) using Python

Question

I'm an admitted noob to Python. I've written a little logger that takes data from the serial port and writes it to a log file. I've got a small procedure that opens the file for append, writes, then closes. I suspect this might not be the best way to do it, but it's what I've figured out so far.

I'd like to be able to have it automagically perform a log-rotate at 00 UTC, but so far, my attempts to do this with RotatingFileHandler have failed.

Here's what the code looks like:

import time, serial, logging, logging.handlers,os,sys
from datetime import *

CT12 = serial.Serial()
CT12.port = "/dev/ct12k"
CT12.baudrate = 2400
CT12.parity = 'E'
CT12.bytesize = 7
CT12.stopbits = 1
CT12.timeout = 3

logStart = datetime.now()
dtg = datetime.strftime(logStart, '%Y-%m-%d %H:%M:%S ')
ctlA = unichr(1)
bom = unichr(2)
eom = unichr(3)
bel = unichr(7)
CT12Name = [ctlA, 'CT12-NWC-test']
CT12Header = ['-Ceilometer Logfile \r\n', '-File created: ', dtg, '\r\n']

def write_ceilo ( text ) :
    f = open ('/data/CT12.log', 'a')
    f.write (text)
    f.close ()

write_ceilo(''.join(CT12Header))

CT12.open()

discard = CT12.readlines()
#print (discard)

while CT12.isOpen():
    response = CT12.readline()
    if len(response) >= 3:
        if response[0] == '\x02' :
            now=datetime.now()
            dtg=datetime.strftime(now, '-%Y-%m-%d %H:%M:%S\r\n')
            write_ceilo(dtg)
            write_ceilo(''.join(CT12Name))
            write_ceilo(response)

What can I do to make this rotate automatically, affixing either a date of rotation, or a serial number, for identification. I'm not looking to rotate any of these out, just keep a daily log file of the data. (or maybe an hourly file?)

Answer 1

For anyone arriving via Google, please don't move the log file out from under the logger while it is in use by calling the system copy of move commands or etc.

What you are looking for is a TimedRotatingFileHandler:

import time

import logging
from logging.handlers import TimedRotatingFileHandler

# format the log entries
formatter = logging.Formatter('%(asctime)s %(name)s %(levelname)s %(message)s')

handler = TimedRotatingFileHandler('/path/to/logfile.log', 
                                   when='midnight',
                                   backupCount=10)
handler.setFormatter(formatter)
logger = logging.getLogger(__name__)
logger.addHandler(handler)
logger.setLevel(logging.DEBUG)

# generate example messages
for i in range(10000):
    time.sleep(1)
    logger.debug('debug message')
    logger.info('informational message')
    logger.warn('warning')
    logger.error('error message')
    logger.critical('critical failure')