Log ¶

Description¶

Create the base ndfc_python logging object

Raises¶

`ValueError`¶

An error is encountered reading the logging config file.
An error is encountered parsing the logging config file.
No formatters are found in the logging config file that are associated with the configured handlers.

`TypeError`¶

develop is not a boolean.

Methods¶

commit()

If config is None, disable logging.

If config is a JSON file conformant with logging.config.dictConfig read the file and configure the base logger instance from the file's contents.

Properties¶

config

Override the NDFC_LOGGING_CONFIG environment variable. Value is an absolute path to a JSON file from which logging config is read. The JSON file must conform to logging.config.dictConfig from Python's standard library.

Type: str()

Default: None

Raises: None

develop

Disable or enable exceptions raised by the logging module.

Type: bool()

Default: False

Raises: TypeError if value is not a bool()

Usage¶

By default, Log() does the following:

Reads the environment variable NDFC_LOGGING_CONFIG to determine the path to the logging config file. If the environment variable is not set, then logging is disabled.
Sets develop to False. This disables exceptions raised by the logging module itself.

Set environment variable¶

Set the environment variable NDFC_LOGGING_CONFIG to the path of the logging config file. bash shell is used in the example below.

set NDFC_LOGGING_CONFIG

export NDFC_LOGGING_CONFIG="/path/to/logging_config.json"

Instantiate `Log()`¶

Instantiate Log() and call commit() on the instance.

instantiate Log()

import logging
from ndfc_python.log_v2 import Log

try:
    logger = Log()
    logger.commit()
except (TypeError, ValueError) as error:
    print(f"Opps! {error}")
    # handle error

At this point, a base/parent logger (ndfc_python) is created. This loggerr is defined in the example logging config file further below.

Create a logger under `ndfc_python`¶

Create log instance

log = logging.getLogger("ndfc_python.myLogger")

Start logging¶

Start logging

log.info("Logger created.")

Disable logging¶

To disable for all children, unset the environment variable.

Disable logging for all ndfc_python child loggers

unset NDFC_LOGGING_CONFIG

Enable exceptions¶

To enable exceptions from the logging module (not recommended, unless needed for development), set develop to True.

set log.develop

from ndfc_python.log_v2 import Log
try:
    log = Log()
    log.develop = True
    log.commit()
except (TypeError, ValueError) as error:
    # handle error

Override NDFC_LOGGING_CONFIG¶

To directly set the path to the logging config file, overriding the NDFC_LOGGING_CONFIG environment variable, set the config property prior to calling commit():

Override NDFC_LOGGING_CONFIG

from ndfc_python.log_v2 import Log
try:
    log = Log()
    log.config = "/path/to/logging_config.json"
    log.commit()
except (TypeError, ValueError) as error:
    # handle error

Example use in a script¶

import sys
from ndfc_python.log_v2 import Log

def main():
    try:
        log = Log()
        log.commit()
    except (TypeError, ValueError) as error:
        print(f"Error setting up the logger: {error}")
        sys.exit(1)

    log.info("Scipt started")

Example use in a class¶

Example use in a class

class MyClass:
    def __init__(self):
        self.class_name = self.__class__.__name__
        self.log = logging.getLogger(f"ndfc_python.{self.class_name}")
    def some_method(self):
        self.log.debug("This is a debug message.")

Logging Config File¶

The logging config file must conform to logging.config.dictConfig from Python's standard library.

An example logging config file is shown below.

$HOME/repos/ndfc-python/lib/ndfc_python/logging_config.json

{
  "version": 1,
  "formatters": {
    "standard": {
      "class": "logging.Formatter",
      "format": "%(asctime)s - %(levelname)s - [%(name)s.%(funcName)s.%(lineno)d] %(message)s"
    }
  },
  "handlers": {
    "console": {
        "class": "logging.StreamHandler",
        "formatter": "standard",
        "stream"  : "ext://sys.stdout"
      },
    "file": {
      "class": "logging.handlers.RotatingFileHandler",
      "formatter": "standard",
      "filename": "/tmp/ndfc-python.log",
      "mode": "a",
      "encoding": "utf-8",
      "maxBytes": 50000000,
      "backupCount": 4
    }
  },
  "loggers": {
        "ndfc_python": {
        "handlers": [
            "console",
            "file"
        ],
        "level": "DEBUG",
        "propagate": false
        },
        "dcnm": {
            "handlers": [
            "file"
            ],
            "level": "DEBUG",
            "propagate": false
        },
        "root": {
            "level": "INFO",
            "handlers": [
            "file"
            ]
        }
    }
}

Log¶