Mixin Context Logger

log_mixin.py

import logging
import os
import uuid
from logging.handlers import TimedRotatingFileHandler
from typing import Dict, List

from pythonjsonlogger import jsonlogger

# root logger
log = logging.getLogger()
log.setLevel(logging.INFO)
file = os.path.join("log", "db_service.json.log")
json_file_handler = TimedRotatingFileHandler(file, backupCount=3, when="MIDNIGHT")
formatter = jsonlogger.JsonFormatter(
    "(levelname) (asctime) (name) (message) (filename) (lineno)"
)
json_file_handler.setFormatter(formatter)
log.addHandler(json_file_handler)


class LogMixin:

    device_id: str
    context_id: str

    __annotations__: Dict[str, type]

    @property
    def log(self) -> "LogMixin.Logger":
        return self

    def set_context_attribute(self, key: str, _type: type) -> None:
        LogMixin.__annotations__[key] = _type

    def _get_context_attributes(self) -> List[str]:
        return [attr for attr in LogMixin.__annotations__ if not attr.startswith("_")]

    @property
    def root_logger(self) -> logging.Logger:
        """
        Override this property to change log handler

        The try-except excplictelty shows that log can be undefined
        """

        try:
            return log
        except NameError as error:
            raise NameError(error)

    def _log(
        self, level, msg, args, exc_info=None, extra=None, stack_info=False
    ) -> None:
        if not self.root_logger.isEnabledFor(level):
            return

        extra = extra if extra is not None else {}
        for attr in [attr for attr in self._get_context_attributes()]:
            if hasattr(self, attr):
                extra[attr] = getattr(self, attr)

        log._log(level, msg, args, exc_info, extra, stack_info)

    def debug(self, msg, *args, **kwargs) -> None:
        self._log(logging.DEBUG, msg, args, **kwargs)

    def info(self, msg, *args, **kwargs) -> None:
        self._log(logging.INFO, msg, args, **kwargs)

    def warning(self, msg, *args, **kwargs) -> None:
        self._log(logging.WARNING, msg, args, **kwargs)

    def error(self, msg, *args, **kwargs) -> None:
        self._log(logging.ERROR, msg, args, **kwargs)

    def exception(self, msg, *args, exc_info=True, **kwargs):
        self.error(msg, *args, exc_info=exc_info, **kwargs)

    def critical(self, msg, *args, **kwargs) -> None:
        self._log(logging.CRITICAL, msg, args, **kwargs)


class TestLogMixin(LogMixin):

    def __init__(self, device_id):
        self.device_id = device_id
        self.context_id = str(uuid.uuid4())[0:4]
        self.name = "John Doe"

        # add random_id to context logger
        self.random_id = str(uuid.uuid4())[0:4]
        self.set_context_attribute("random_id", str)

    def say_hello(self):
        self.log.info(
            "Hello World", extra={"appliance_state_id": str(uuid.uuid4())[0:4]}
        )


TestLogMixin(device_id="foo").say_hello()


"""
OUTPUT:
> 2019-01-23 15:04:04,807", "name": "root", "message": "Hello World", "filename": "log_mixin.py", "lineno": 70, "appliance_state_id": "77bf", "device_id": "foo", "context_id": "0c07", "random_id": "a030"}

Note that filename and lineno are not accurate anymore.
"""