flask_log.py

#!/usr/bin/env python
"""
Setup a nice formatter, configurable level, and syslog handler for logging.
"""

import logging
from logging.handlers import SysLogHandler
import os
import platform


class Logging(object):
    """Configure flask logging with nice formatting and syslog support."""

    def __init__(self, app=None):
        """Boiler plate extension init with log_level being declared"""
        self.log_level = None
        self.app = app
        if app is not None:
            self.init_app(app)

    def init_app(self, app):
        """Setup the logging handlers, level and formatters.

        Level (DEBUG, INFO, CRITICAL, etc) is determined by the
        app.config['FLASK_LOG_LEVEL'] setting, and defaults to
        ``None``/``logging.NOTSET``.

        """
        config_log_level = app.config.get('FLASK_LOG_LEVEL', None)

        # Set up format for default logging
        hostname = platform.node().split('.')[0]
        formatter = (
            '[%(asctime)s] %(levelname)s %(process)d [%(name)s] '
            '%(filename)s:%(lineno)d - '
            '[{hostname}] - %(message)s'
        ).format(hostname=hostname)

        config_log_int = None
        set_level = None

        if config_log_level:
            config_log_int = getattr(logging, config_log_level.upper(), None)
            if not isinstance(config_log_int, int):
                raise ValueError(
                    'Invalid log level: {0}'.format(config_log_level)
                )
            set_level = config_log_int

        # Set to NotSet if we still aren't set yet
        if not set_level:
            set_level = config_log_int = logging.NOTSET
        self.log_level = set_level

        # Setup basic StreamHandler logging with format and level (do
        # setup in case we are main, or change root logger if we aren't.
        logging.basicConfig(format=formatter)
        root_logger = logging.getLogger()
        root_logger.setLevel(set_level)

        # Get everything ready to setup the syslog handlers
        address = None
        if os.path.exists('/dev/log'):
            address = '/dev/log'
        elif os.path.exists('/var/run/syslog'):
            address = '/var/run/syslog'
        else:
            address = ('127.0.0.1', 514)
        # Add syslog handler before adding formatters
        root_logger.addHandler(
            SysLogHandler(address=address, facility=SysLogHandler.LOG_LOCAL0)
        )
        self.set_formatter(formatter)

        return config_log_int

    @staticmethod
    def set_formatter(log_formatter):
        """Override the default log formatter with your own."""
        # Add our formatter to all the handlers
        root_logger = logging.getLogger()
        for handler in root_logger.handlers:
            handler.setFormatter(logging.Formatter(log_formatter))