How can I rename "levelname" to "level" in Python log messages?

Question

I have a Python logging configuration which looks like this:

LOGGING_CONFIG:
    version: 1
    formatters:
        human:
            class: logging.Formatter
            format: '[%(asctime)s]:[%(levelname)s]: %(message)s'
        json:
            class: pythonjsonlogger.jsonlogger.JsonFormatter
            format: '%(asctime)s %(levelname)s %(message)s'
    handlers:
        console:
            class: logging.StreamHandler
            level: DEBUG
            formatter: json  # change this to 'human' when you run it locally, json in production
        file:
            class: logging.FileHandler
            filename: logfile.log
            level: DEBUG
            formatter: json
    root:  # Logging for 3rd party stuff
        level: INFO
        handlers:
            - console
            - file
    project_name:  # Logging this module
        level: DEBUG
        handlers:
            - console
            - file

For another system, I need the structured logging to have some fixed names. One example is that it should not be levelname, but level. How can I rename log fields?

What I have:

{"asctime": "2018-10-22 14:50:19,923", "levelname": "info", "message": "foobar"}

What I want:

{"asctime": "2018-10-22 14:50:19,923", "level": "info", "message": "foobar"}

Answer 1

levelname will not appear in normal Python loggers but in the custom formatter you used. From what I understood you could use below snippet to customize the dict it outputs:

class CustomJsonFormatter(jsonlogger.JsonFormatter):
    def add_fields(self, log_record, record, message_dict):
        super(CustomJsonFormatter, self).add_fields(log_record, record, message_dict)
        log_record['level'] = log_record['levelname']
        del log_record['levelname']

Then replace pythonjsonlogger.jsonlogger.JsonFormatter with the address of CustomJsonFormatter.