0%
March 7, 2022

Customized Logger in Python and Javascript

javascript

python

Contents

In Python

This python logger not only log the message in the console, it also pipes all the message inside a file which we can review as long as this file is saved in a volume.

import logging
import datetime
import os
from utils.get_config import get_config

def create_logger(log_dir,logging_level=logging.INFO):
    if not os.path.exists(log_dir):
        os.makedirs(log_dir)

    logger = logging.getLogger()
    logger.setLevel(logging_level)
    formatter = logging.Formatter(
        '[%(levelname)1.1s %(asctime)s %(module)s:%(lineno)d] %(message)s',
        datefmt='%Y%m%d %H:%M:%S')

    sh = logging.StreamHandler()
    sh.setLevel(logging_level)
    sh.setFormatter(formatter)

    log_filename = datetime.datetime.now().strftime("%Y-%m-%d_%H_%M_%S.log")
    fh = logging.FileHandler(os.path.sep.join([log_dir, log_filename]))
    fh.setLevel(logging_level)
    fh.setFormatter(formatter)

    logger.addHandler(sh)
    logger.addHandler(fh)

    return logger

logger_dir = get_config("log_dir", "sbg-logs")
logger = create_logger(logger_dir)

In javascript

Unlike python, we will use npm package tracer to customize the logger as follows:

import tracer from "tracer";
import fs from "fs";
import path from "path";
const date = new Date();
const year = date.getFullYear();
const month = date.getMonth();
const day = date.getDate();
const hour = date.getHours();
const mins = date.getMinutes();
const seconds = date.getSeconds();
const dateString = `${year}-${month}-${day}_${hour}-${mins}-${seconds}`;
const logFileDir = "./logs";
const logFileLocation = path.join(logFileDir, `${dateString}.log`);

if (!fs.existsSync(logFileDir)) {
  fs.mkdirSync(logFileDir);
}
if (!fs.existsSync(logFileLocation)) {
  fs.open(logFileLocation, "w", () => {});
}

const logger = tracer.colorConsole({
  transport: function (data) {
    fs.createWriteStream(logFileLocation, {
      flags: "a",
      encoding: "utf-8",
      mode: 0o666,
    }).write(data.rawoutput + "\n");
  },
  format: [
    "[{{timestamp}}-<{{title}}>-{{file}}:{{line}}] {{message}}", //default format
    {
      error:
        "[{{timestamp}}-<{{title}}>-{{file}}:{{line}}] {{message}} \nCall Stack:\n{{stack}}", // error format
    },
  ],
  dateformat: "HH:MM:ss.L",
  preprocess: function (data) {
    data.title = data.title.toUpperCase();
  },
});

export default logger;