Python Logging and Rotating Files
I Have a Python Program That Is Writing to a Log File That Is Being Rotated by Linux's Logrotate Command. When This Happens I Need to Signal My Program to Stop...
I have a python program that is writing to a log file that is being rotated by Linux's logrotate command. When this happens I need to signal my program to stop writing to the old file and start writing to the new one. I can handle the signal but how do I tell python to write to the new file?
I am opening the file like this:
logging.basicConfig(format='%(asctime)s:%(filename)s:%(levelname)s:%(message)s',filename=log_file, level=logging.INFO)
and writing to it like this:
logging.log(level,"%s" % (msg))
The logging modules look very powerful but also overwhelming. Thanks.
4 Answers
Don't use logging.basicConfig, use WatchedFileHandler. Here's how to use it.
import time
import logging
import logging.handlers
def log_setup():
log_handler = logging.handlers.WatchedFileHandler('my.log')
formatter = logging.Formatter(
'%(asctime)s program_name [%(process)d]: %(message)s',
'%b %d %H:%M:%S')
formatter.converter = time.gmtime # if you want UTC time
log_handler.setFormatter(formatter)
logger = logging.getLogger()
logger.addHandler(log_handler)
logger.setLevel(logging.DEBUG)
log_setup()
logging.info('Hello, World!')
import os
os.rename('my.log', 'my.log-old')
logging.info('Hello, New World!')
You may want to look at WatchedFileHandler to implement this, or as an alternative, implement log rotation with RotatingFileHandler, both of which are in the logging.handlers module.
from logging import handlers
handler = handlers.TimedRotatingFileHandler(filename, when=LOG_ROTATE)
handler.setFormatter(logging.Formatter(log_format, datefmt="%d-%m-%Y %H:%M:%S"))
#LOG_ROTATE = midnight
#set your log format
This should help you in handling rotating log
Since rotation is already being done by logrotate, in your signal handler you should just call logging.basicConfig(...) again and that should reopen the log file.
Alexander Ross has covered the video game industry for a decade, writing deep dives on game design, esports tournaments, VR developments, and gaming culture.
