Lori

Lori is a very lightweight logger for use in Node.js applications, with a middleware option for Express access logs. Lori is a colourful way to output quick logging, and is extremely easy to set up. It's not designed to take on the functionality of other libraries such as morgan, but to get something in place quickly which can provide insight into your application.

Compatibility

This module is built on each commit with TravisCI on the latest stable version of Node.js, although the main module is compatible all the way back to 0.8.

Usage

Lori is available on npm, so simply install it.

$ npm install lori

There are a couple of ways you can use Lori, either as a generic logger or as a piece of Middleware for Express.

Middleware

As middleware, Lori will generate access logs for your Express application in the following format:

[Thu, 13 Aug 2015 19:14:09] [INFO]  GET /welcome 544.98ms

To set up Lori as a piece of Middleware, simply drop it into your app as early as possible in your setup:

var lori = require('lori');

app.use(lori.express());

Logging

There are several default methods written into Lori, for the common use cases with logging:

lori.debug('test');
lori.error('test');
lori.info('test');
lori.warn('test');

// [Thu, 13 Aug 2015 19:14:09] [DEBUG] test
// [Thu, 13 Aug 2015 19:14:09] [ERROR] test
// [Thu, 13 Aug 2015 19:14:09] [INFO]  test
// [Thu, 13 Aug 2015 19:14:09] [WARN]  test

These methods typically take String arguments, however if a non-String argument is provided, Lori will JSON.stringify whatever is passed.

You can also call the access function the Express Middleware uses, as below:

// [request]
lori.access(req);

// [verb, url, duration(hrtime)]
lori.access('GET', '/welcome', process.hrtime(startTime));

Each level has a colour associated with it (which can be changed, see below). By default all logs go to stdout, but this can also be modified.

Configuration

Lori is extremely easy to use, with a few little utilities to allow for customisation.

Constructor

By default, the lori module provides a singleton logger for use throughout your application (it doesn't care about state), however if you wish to make many loggers, you can access the constructor as below:

var lori = require('lori');

var Logger = new lori.Logger();

This allows you to have different loggers with different configurations throughout your application.

Configure

The configure function is typically called as soon as you start your application - it allows you to specify colours, logging locations, formats, etc. This function takes an object argument of the following options:

lori.configure({

    // The format the date string will take at
    // the start of dated logs. This defaults to
    // a UTC style JavaScript string. Formats are
    // controlled via MomentJS, so see their docs
    // for examples.
    dateFormat: 'ddd, DD MMM YYYY HH:mm:ss',

    // By default, all timestamps are in UTC time,
    // but this can be changed by setting this value
    // to true. If true, dates will use the local time
    // via the default moment constructor.
    localTime: false,

    // Simply a flag of whether you wish to enable
    // colored output or not. If writing to a file,
    // this should usually be false.
    logColors: true,

    // This is the low-level log function used by Lori
    // when outputting logs. By default, logs go straight
    // to console.log (as shown), however it can be
    // overridden to write to files, etc. When writing to
    // files, it's a good idea to turn off colours.
    //
    // The `str` arguments passed to this method is the
    // final string after all formatting by Lori. The `msg`
    // argument is the original log message (without colors),
    // and the `lvl` argument is the level called, e.g. 'debug'
    //
    // This allows for flexible overrides, without adding a
    // tonne of infrastructure.
    log: function(str, msg, lvl){
        console.log(str);
    },

    // This is the theme used for each type of logger. If
    // any of these values are unset, they will have their
    // colours removed. Colours are provided by the npm
    // module `colors`, so visit their docs to see the valid
    // strings.
    //
    // The bottom four keys shown here are part of the access
    // logs in the Express middleware - you can control each
    // part of the log output.
    theme: {
        debug: 'yellow',
        error: 'red',
        info: 'green',
        warn: 'yellow',

        verb: 'white',
        path: 'cyan',
        message: 'white',
        duration: 'white'
    }

});

Modification

This is not the only time you can control Lori though, it's dynamic - you can modify it at any time, although naturally it will only effect the instance you're working with (instead of all of them):

// Reset Lori to the default state (as shown in the above `configure`)
lori.reset();

// Modify to use a new logging method on the underlying instance.
//
// This example will output a colored string to the console in
// non-production environments, and log to a file in production
// environments. The log file is based on the log level.
lori.setLogger(function(str, msg, lvl){
    if(app.get('env') !== 'production'){
        console.log(str);
    } else {
        fs.appendFileSync('./' + lvl  + '-logs.txt', msg);
    }
});

// Change the date format
lori.setDateFormat('DD-MM-YYYY');

// Change the theme used for colours - this will overwrite the previous theme
lori.setTheme({
    info: 'blue'
});

// Change the theme used for colours - this will merge with the previous theme
lori.updateTheme({
    info: 'blue'
});

// Turn off coloured output
lori.useColors(false);

// Switch to using local time
lori.useLocalTime(true);

Tests

Tests are written in Mocha, and can be run via npm scripts.

$ npm test

You can also generate coverage reports in HTML and lcov formats using:

$ npm run coverage
$ npm run lcov

Sadly, couldn't use Grunt because it swallows the colours.

Issues

If you find any issues inside this module, feel free to open an issue here.