Django: Pass variable to logging in settings file

Question

I am trying to add a variable to my log line through my settings.py file.

This is the code in settings (the logging part):

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'mail_admins': {
                        'level': 'CRITICAL',
                         'class': 'django.utils.log.AdminEmailHandler'
                        },

        'customhandler':{
                        'level':'DEBUG',
                        'class':'logging.RotatingFileHandler',
                        'formatter':'custom_format',
                        'filename':LOG_LOCATION
                        },
                 },

     'loggers': {
         'django.request': {
                        'handlers': ['mail_admins'],
                         'level': 'CRITICAL',
                        'propagate': True,
                            },
         'Logger_Custom1': {
                        'handlers':['customhandler'],
                        'level':'DEBUG',
                        'propagate':True
                           },
                 },

    'formatters': {
        'verbose': {
            'format': '%(levelname)s %(asctime)s %(module)s %(process)d %(thread)d %(message)s'
                     },
         'simple': {
            'format': '%(levelname)s %(message)s'
                     },
         'custom_format':{
            'format':'[%(asctime)s %(levelname)s T:%(threadName)s F:%(funcName)s ] %(message)s '
                         },
                 }
}

The above code is working fine, but now I would like each log message to have a variable at the end. Something like:

MyVariable = "Somelines" 
[%(asctime)s %(levelname)s T:%(threadName)s F:%(funcName)s ] %(message)s 'MyVariable

So my log would have that variable's contents at the end of each logging line. I know we can do that inside the view function like this: logging.warning('% before you %','Look','Leap') But that will require us to include that line everywhere separately. Also, when we need to add or change that variable name, we will need to change that line everywhere in every file.

So I was wondering if there is any way to do that directly from settings.py, so that we can make one change and it will apply to all logging messages.

Answer 1

I found out the solution by myself. I don't know if this is a good practice, but it works.

All I did was assign a variable:

testvar = "MyVariable"

And then append this variable, like this:

'format': '%(levelname)s %(asctime)s %(module)s %(process)d %(thread)d %(message)s ' + testvar

The output will have the variable in your log entry merged with the log format. Thank you. Please let me know if there are more ways to do it.

Answer 2

The log format string you're referring to has a number of variables that the logging module supplies. The full list is here. Essentially, it passes a dictionary into the string for formatting - and you are unable to manipulate that list. Instead, you should "hardcode" your variable either directly within the format string as it's actual value, or store the value within a variable within your settings file, and just append it.

'format': '%(levelname)s %(asctime)s %(module)s %(process)d %(thread)d %(message)s and look, custom stuff here!!!'

Or..

custom = 'and look, custom stuff here!!!'
'format': '%(levelname)s %(asctime)s %(module)s %(process)d %(thread)d %(message)s ' + custom