JSON Structured Logger

PyBayFormatter.py

import json
import logging
import sys


logger = logging.getLogger(__name__)


class PyBayFormatter(logging.Formatter):
    """Implementation of JSON structured logging that works for most handlers."""

    def format(self, record: logging.LogRecord) -> str:
        """Overrides parent format function.

        :param record: logging.LogRecord object
        :return: JSON string
        """
        payload = self.make_structured_dict(record)
        if hasattr(record, 'exc_info') and record.exc_info:  # adds stack traces!
            payload['stack_trace'] = self.formatException(record.exc_info)
        return json.dumps(payload)

    @staticmethod
    def make_structured_dict(record: logging.LogRecord) -> dict:
        """Creates dictionary that we want to JSON-ify.

        :param record: the LogRecord object.
        :return: dict
        """
        message_str = record.getMessage()  # this interpolates it with '%'.
        if isinstance(record.args, dict):  # handles case for backwards compatibility of people passing multiple args.
            user_payload = record.args
        else:
            user_payload = {'value': repr(record.args)}
        return {
            'payload': user_payload,
            'message': message_str,
            'version': '0.0.1',  # always good to have a schema version field
            'meta': {
                'level': record.levelname,
                'name': record.name,
                'pid': record.process,
                'code': {
                    'file_name': record.filename,
                    'file_url': record.pathname,
                    # etc ...
                },
            }
        }
        
if __name__ == '__main__':
    ch = logging.StreamHandler(sys.stdout)
    logger.addHandler(ch)
    ch.setFormatter(PyBayFormatter())
    logger.setLevel(logging.INFO)
    client_id = 3
    shipment_id = 11110
    item_id = 120001
    logger.info('Computing scores for item_id: [%(item_id)s] client_id: [%(client_id)s] shipment_id: [%(shipment_id)s]',
                {'client_id': client_id, 'item_id': item_id, 'shipment_id': shipment_id})