sds-simple-logger v2.1.0

Simple Logger

Lightweight, Simple library to write logs. Writes to console and file by default.

Introduction

Simple logger is a simple library used to log to console and file. The usage is very simple, import the class and initialize it. You can use various logging methods available to create logs. Please note that initialization of logger is required and will throw an error when you use one of the available logging methods without first initializing the logs. If initialization was successful, it return true else throws an error. All operation related to files ex: writing to files, creation of file are synchronous.

import Logger from 'sds-simple-logger';

// Throw error if there was problem initializing logs using defaults
Logger.initLogs();

Logger.debug('Debug log');
Logger.info('Some info message');
Logger.warn('Some warning message');
Logger.error(new Error('Error message'));

Once imported and initialized, you can use it in any other file:

import Logger from 'sds-simple-logger';
// or
const Logger = require('sds-simple-logger');

Logger.log('Test logs');

Sample Output beautified JSON:

{
  "timestamp": "Fri, 15 Jan 2021 22:12:04 GMT",
  "type": "DEBUG",
  "message": "Fri Jan 15 2021 17:12:04 GMT-0500 (GMT-05:00) debug log"
}

String JSON output:

{"timestamp":"Fri, 15 Jan 2021 22:15:14 GMT","type":"LOG","message":"Test dir creation"}

String output:

Fri, 15 Jan 2021 22:14:17 GMT DEBUG: Fri Jan 15 2021 17:14:17 GMT-0500 (GMT-05:00) debug log

Options:

You can pass various options as an options object when initializing the logger. Options available:

1. cycleTime: The time in milliseconds after which a new log file should be created, defaults to 86400000 ms or 24 hrs
2. removeTime: The time in milliseconds, log files older than this will be removed. It runs with the cycle time, defaults to 604800000 ms or 7 days
3. logsDir: The path and name of logs directory. Defaults to creation of logs directory in the current directory
4. writeToFile: By default all logs are written to file and console. If this is set to false logs will be only written to console. It is set to true by default.
5. writeToConsole: By default all logs are written to file and console. If this is set to false, logs will be only written to the logs file. It is set to true by default.
6. json: By default all logs are written as JSON object to console and file. You can set this to false to write log string instead.
7. beautifyJson: By default JSON object written to console and logs are beaufied or in other words formated for readibility. Is this option is set to false, logs will still be written in JSON format but will not beautified while writting.
8. handleSyncErrors: By default set to true logger while throw and error if a sync operation such as writting to file fails. If set to false the logger will not throw error but it will just print a error to the console.

Example:

Logger.initLogs({
  cycleTime: 86400000,
  removeTime: 86400000,
  logsDir: path.join(__dirname, '../test-logs'),
  logName: 'test.logs',
  writeToFile: true,
  writeToConsole: true,
  json: true,
  beautifyJson: true,
  handleSyncErrors: true,
});

Methods Available:

All the methods available can take variable string messages or in other words are variadic functions except the error method, which takes only error object as input. For the error methods available you can pass a second argument i.e a boolean value of true. If you want to log the error and exit the Node process.

Debug

Prints DEBUG in front the logs. Sample output: Tue, 05 Jan 2021 06:12:49 GMT: DEBUG: Debug output test

Usage:

// Signature of function
// (...messages: string[])
// Throw error if there was problem writing to logs

Logger.debug('Debug test');
Logger.debug('Debug test one', 'Debug test two', 'Debug test three');

Info

Prints INFO in front the logs. Sample output: Tue, 05 Jan 2021 06:13:18 GMT: INFO: Info output test

Usage:

// Signature of function
// (...messages: string[])
// Throw error if there was problem writing to logs

Logger.info('Info test');
Logger.info('Info test one', 'Info test two', 'Info test three');

Log

Prints LOG in front the logs. Sample output: Tue, 05 Jan 2021 06:13:18 GMT: INFO: Info output test

Usage:

// Signature of function
// (...messages: string[])
// Throw error if there was problem writing to logs

Logger.log('Log test');
Logger.log('Log test one', 'Log test two', 'Log test three');

Warn

Prints WARN in front the logs. Sample output: Tue, 05 Jan 2021 06:13:18 GMT: WARN: Warn output test

Usage:

// Signature
// (...messages: string[])
// Throw error if there was problem writing to logs

Logger.warn('Warn test');
Logger.warn('Warn test one', 'Warn test two', 'Warn test three');

Error

Prints Error in front the logs and also prints the error stack. Along with this it also print a unique error key. If you want to exit the node process after printing the error pass true as the second arg. Sample output:

Tue, 05 Jan 2021 06:13:18 GMT: ERROR KEY: 1609827198551
Error: Error output test
  at main (/Users/someuser/Projects/Personal/Testing/index.ts:7:16)
  at Object.<anonymous> (/Users/someuser/Projects/Personal/Testing/index.ts:11:1)
  at Module.\_compile (internal/modules/cjs/loader.js:1015:30)
  at Module.m.\_compile (/usr/local/lib/node_modules/ts-node/src/index.ts:858:23)
  at Module.\_extensions..js (internal/modules/cjs/loader.js:1035:10)
  at Object.require.extensions.<computed> [as .ts] (/usr/local/lib/node_modules/ts-node/src/index.ts:861:12)
  at Module.load (internal/modules/cjs/loader.js:879:32)
  at Function.Module.\_load (internal/modules/cjs/loader.js:724:14)
  at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)
  at main (/usr/local/lib/node_modules/ts-node/src/bin.ts:227:14)

Usage:

// Signature
// (error: Error, exit: boolean = false): number;
// Throw error if there was problem writing to logs

Logger.error(new Error('Error test'));
// Exit the node process with non-zero exit code
Logger.error(new Error('Error test'), true);

Prune Logs

To prune logs i.e deleting the log directory and its content. You can use the pruneLogs method available on the logger instance. Method returns true if successfully deleted.

The next time you use a logging method available. The logs directory will be created according to the options passed in the initLogs() function.

Logger.pruneLogs();

Express Request Logger Middelware

A small middleware function to log Express requests. Pass it before your routes to log all incoming requests. It will write to the same log file as the logger.

// Get the request logging middleware
const loggerMiddleware = Logger.expressReqLogs();

// Use the middleware with express app
app.use(loggerMiddleware);

// Output to console:
REQ LOGS: {"timestamp":"Tue, 12 Jan 2021 06:30:02 GMT","request":{"method":"GET","url":"test.com","clientIp":null,"ipFamily":null,"userAgent":null,"httpVersion":null,"params":{},"headers":{"token":"Test","random":"Random"},"body":{"username":"Test","password":"Test"}}}

Middleware options:

By default it pics the options passed in initLogs method of the logger, but those options can be overwritten by passing an options object. In other words, you can pass a options object when calling the Logger.expressReqLogs() to configure the logger middleware. Avaliable options are:

1. writeToFile: Boolean value, set to true by default
2. writeToConsole: Boolean value, set to true by default
3. json: Boolean value, set to true by default
4. hideBodyFields: Array of fields that you want to hide on the the request body. Hidden fields/keys and respective values won't be printed in logs
5. hideHeaders: Arrays of headers you want to hide

// Call with options
Logger.expressReqLogs({
  writeToFile: true,
  writeToConsole: true,
  json: true,
  hideBodyFields: ['password'],
  hideHeaders: ['token'],
  handleSyncErrors: true,
});

// Use the middleware with express app
app.use(loggerMiddleware);

Sample String output:

Fri, 15 Jan 2021 22:12:04 GMT, REQUEST: method - GET, url - test.com, clientIp - null, ipFamily - null, userAgent - null, httpVersion - null, params - {}, headers - {"random":"Random"}, body - {"username":"Test"}

Sample JSON string output:

{"timestamp":"Fri, 15 Jan 2021 22:15:14 GMT","type":"REQUEST","method":"GET","url":"test.com","clientIp":null,"ipFamily":null,"userAgent":null,"httpVersion":null,"params":{},"headers":{"random":"Random"},"body":{"username":"Test"}}

Sample Pretty JSON Output:

{
  "timestamp": "Fri, 15 Jan 2021 22:10:52 GMT",
  "type": "REQUEST",
  "method": "GET",
  "url": "test.com",
  "clientIp": null,
  "ipFamily": null,
  "userAgent": null,
  "httpVersion": null,
  "params": {},
  "headers": {
    "random": "Random"
  },
  "body": {
    "username": "Test"
  }
}