Change log file name in logger module globally

Question

I'm using logger module with dictConfig (with a yaml file) for my application logging. However, I would to change the log file name globally by adding a date prefix (ex: logpath: /foo/bar/file_20150523.log).

So each time I start my application a new log file is created.

Is it possible in one way of another to do it inside the yaml file or I need to modify the handler in my application ?

Thanx

Answer 1

The idea is simple:

1. Read configuration from a YAML file
2. Locate the name of the log file
3. Append the date stamp to the name part (not the extension part)
4. Call logging.config.dictConfig and pass in the modified configuration dictionary

Here is the YAML file I use for this example, daily_log_file.yaml :

version: 1
loggers:
    default_logger:
        handlers: [consoleHandler, fileHandler]
        level: DEBUG
handlers:
    consoleHandler:
        class: logging.StreamHandler
        level: DEBUG
        formatter: brief
    fileHandler:
        class: logging.FileHandler
        formatter: brief
        filename: '/tmp/daily_log_file.log'
        level: DEBUG
formatters:
    brief:
        format: '%(levelname)8s %(message)s'

Here is the script, daily_log_file.py :

import datetime
import os
import logging
import logging.config
import yaml

def yaml_config(yaml_filename):
    global config_dict
    with open(yaml_filename) as f:
        config_dict = yaml.load(f)

        # Append the date stamp to the file name
        log_filename = config_dict['handlers']['fileHandler']['filename']
        base, extension = os.path.splitext(log_filename)
        today = datetime.datetime.today()
        log_filename = '{}{}{}'.format(
            base,
            today.strftime('_%Y%m%d'),
            extension)
        config_dict['handlers']['fileHandler']['filename'] = log_filename

        # Apply the configuration
        logging.config.dictConfig(config_dict)

if __name__ == '__main__':
    yaml_config('daily_log_file.yaml')
    logger = logging.getLogger('default_logger')
    logger.debug('debug message')
    logger.info('info message')

Discussion

• yaml_config is where the action is. I first load the configuration dictionary from the YAML file, then patch up the file name
• To patch up the file name, I separate the base file name and extension
• I then get today's date and append the time stamp to the file name, then assign the result back to the configuration dictionary
• Finally, I called dictConfig to finish the job