Simple and uniform logging in AWS Lambda

index.py

import json
import logging
import os
import sys


class SuppressFilter(logging.Filter):
    def __init__(self, logger):
        self.logger = logger

    def filter(self, record):
        logger = record.name
        return False if self.logger in logger else True


class LambdaLogger(logging.LoggerAdapter):
    LOG_LEVEL = os.getenv('LOG_LEVEL') or 'INFO'
    LOG_FORMAT = os.getenv('LOG_FORMAT') \
        or '%(levelname)s RequestId: %(reqid)s %(message)s'

    def __init__(self, name, level=None, format_string=None):
        logger = logging.getLogger(name)
        formatter = logging.Formatter(format_string or self.LOG_FORMAT)

        for handler in logger.handlers:
            handler.setFormatter(formatter)
        else:
            handler = logging.StreamHandler(sys.stdout)
            handler.setFormatter(formatter)
            logger.addHandler(handler)

        for handler in logging.root.handlers:
            handler.addFilter(SuppressFilter(name))

        super().__init__(logger, dict(reqid=None))

        self.setLevel(level or self.LOG_LEVEL)

    def addContext(self, context=None):
        if context:
            self.extra.update(reqid=context.aws_request_id)


logger = LambdaLogger(__name__)


def handler(event, context=None):
    logger.addContext(context)
    logger.info(json.dumps(event))
    logger.warning('HELP!')

# >>> handler({'fizz': 'buzz'}, context)
# START RequestId: 8141a733-1269-4356-8aee-e2a66ce8014c Version: $LATEST
# INFO RequestId: 8141a733-1269-4356-8aee-e2a66ce8014c {"fizz": "buzz"}
# WARNING RequestId: 8141a733-1269-4356-8aee-e2a66ce8014c HELP!
# END RequestId: 8141a733-1269-4356-8aee-e2a66ce8014c
# REPORT RequestId: 8141a733-1269-4356-8aee-e2a66ce8014c	Duration: 1.66 ms	Billed Duration: 2 ms	Memory Size: 128 MB	Max Memory Used: 52 MB	Init Duration: 123.10 ms