llog

llog is a simple logging module. llog is intended for use in applications, not libraries. It provides level-based debugging (trace|debug|info|warn|error|fatal). note: For adding detailed debug statements in libraries, use TJ's debug module.

As an added bonus, llog provides a simple upgrade path from plain text to json logging via either pino or bunyan. llog will look for pino or bunyan at load time and automatically use them as a provider if present. This means you can write your apps with non-json logging when starting, and auto-magically all your logs to json logging with a simple npm i --save pino.

level-based debugging

To use llog:

var log = require('llog');

log.debug('some info'); // prints 'debug some info' to stdout
log.info('some info'); // prints 'info some info' to stdout
log.warn('some info'); // prints 'warn some info' to stdout
log.error('some error'); // prints 'error some error' to stdout

Specifying log levels

llog is based on debug, and as such extends the same mechanism debug uses to specify which items to log - using process.env.DEBUG.

To log only info, warn, and error in llog, for instance, you would run your application similar to the following:

DEBUG=info,warn,error node app.js

Adding trace is simple:

DEBUG=trace,info,warn,error node app.js

Magic upgrade to json logging

llog will automatically detect if bunyan or pino are installed as a peer dependency and, if so, automatically upgrade to json logging. Because bunyan and pino use process.env.LOG_LEVEL as a level indicator (as opposed to debug's DEBUG variable, the steps for moving to json logs are:

1. npm install --save buynan or npm install --save pino
2. execute your application using LOG_LEVEL=10 node app instead of using DEBUG. Higher levels are always included when specifying a level.

Bunyan log levels can be found at https://github.com/trentm/node-bunyan#levels. Pino log levels can be found at https://github.com/pinojs/pino

This is particularly useful when moving from early stages of application development to having unified logging via Logstash or Splunk.