@5app/logger

logger

Simple console logger that outputs json in prod and pretty messages on dev

Usage

npm install --save @5app/logger

Then, generate a logger in your app and use it to log messages.

const {logger} = require('@5app/logger');

logger.info('An email was sent', {
  email: '[e-mail]',
  template: 'template1',
});

logger.error(new Error('Unknown playlist 123'));

Alternatively, you can create a new instance of logger where you can specify the metadata, logging level, and whether you want simple logs or not:

const {getLogger} = require('@5app/logger');

const logger = getLogger({
  simple: process.env.NODE_ENV === 'development',
  metadata: {
    tag: process.env.TAG, // release tag, e.g. docker container tag
  },
});

logger.info('An email was sent', {
  email: '[e-mail]',
  template: 'template1',
});

logger.error(new Error('Unknown playlist 123'));

Options

The logger generator accepts the following options:

simple

This boolean value specifies whether we should log pretty dev-friendly messages instead of JSON or not. By default, simple will be false.

Example:

const {getLogger} = require('@5app/logger');

// This logger will log dev-friendly messages
const logger = getLogger({
  simple: true,
});

The default logger uses the environment variable LOGS_FORMAT to determine if the logs are going to be generated in json (json) or simple console logs (any other value other than json).

metadata

Metadata is an object containing service metadata like the release tag or the A/B testing experiment we are running. This object will be added to each log entry when using the JSON mode.

Example:

const {getLogger} = require('@5app/logger');

// This logger will add details about the current release and A/B experiment to every log line
const logger = getLogger({
  metadata: {
    release: '1.2.3',
    experiment: 12345,
  },
});

level

You can specify a minimum logging level using the level parameter or using the LOGS_LEVEL environment variable. By default, the logging level will be debug (npm).

Example:

const {getLogger} = require('@5app/logger');

// This logger will add details about the current release and A/B experiment to every log line
const logger = getLogger({
  level: 'warn',
});

logger.info('this message will not be logged');
logger.warn('you will see this message');

Changelog

1.1.0 (2019-09-12)

Features

• Provide a logger instance by default (6a932d6)