Pretty Node.js logging.
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README.md

Cedar

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Cedar is a Node.js log, designed to be fast, extensible, and super useful.

Powerful features

  • Modifiable logging prefixes, formatters, and stringify functions.
  • Logs which are functions, allowing shorthand calls.
  • A console transport with color unicode symbols and helpful code snippets inside stack traces.
  • A file transport that can rotate by day, hour or minute.
  • A multi transport, which supports cluster, sending worker logs to the master process.

Quick Start

Add cedar to your dependencies.

npm install --save cedar

Create a log, and use it.

var log = require('cedar')([
  {
    transport: 'console' // Default.
    level: 'trace' // Default.
  },
  {
    transport: 'file',
    level: 'info',
    path: 'log/${YYYY}/${MM}/${DD}/app_${HOST}.log'
  }
]);

log('Log a string'); // Shorthand.
log.debug(['or', 'an', 'array']);
log.trace({or: 'JSON of course'});
log.log('and', 'multiple', 'arguments', 'are', 'supported.', true);
log.info('This message will also log to file, based on `level`.')

log.trace('This gets formatted as a trace message, with a stack trace');
log.debug('This gets formatted as a debug message.');
log.log('This gets formatted as a log message.');
log.info('This gets formatted as an info message.');
log.warn('This gets formatted as a warning message.', error);
log.error('This gets formatted as an error message.', error);
log.fatal('This gets formatted as a fatal error message.', error);

Convention & Configuration

Each Cedar transport has properties with defaults that can be overridden using a config object. They also have getters and setters, allowing you to change them later.

For example:

// Set the log `level` in a configuration object.
var log = require('cedar')({level: 'warn'}); // "warn", "error" and "fatal".

log('log');         // Ignore.
log.error('error'); // Log "error".

// Assign the `level`, thereby invoking its setter.
log.level = 'debug';

log('log');         // Log "log".
log.error('error'); // Log "error".
log.trace('trace'); // Ignore.

log.level string

Configures the minimum level of logging that is shown (default: trace).

var log = require('cedar')();
log.level = 'debug';

Setting to a level from this list will enable logs of that level and all of the levels after it: debug, trace, log, info, warn, error and fatal. Setting the level to nothing will stop all logs.

log.prefixes object

Customize prefixes for the color log messages.

require('colors');

var log = require('cedar')();
log.prefixes = {
  trace: 'TRACE: '.cyan,
  debug: 'DEBUG: '.magenta,
  log:   'LOG:   '.grey,
  info:  'INFO:  '.green,
  warn:  'WARN:  '.yellow,
  error: 'ERROR: '.red,
  fatal: 'FATAL: '.red
};

log.space string

Configures the spacing that stringify uses.

var log = require('cedar')();
log.space = '  ';

The default is two spaces.

log.format function

Customize the message format, given 3 arguments.

var log = require('cedar')();
log.format = function (message, prefix, type) {
  return prefix + message + ' from log.' + type + '!';
});
log.info('Hello'); // "INFO Hello from log.info!"

Transports

Cedar currently supports 4 main transports: "base", "console", "file" and "multi". Each transport takes an optional configuration object.

Base

The base transport writes to a stream, and other transports extend it.

var fs = require('fs');
var writeStream = fs.createWriteStream('my.log');
var base = require('cedar')('base', {stream: writeStream});
base.log('Write this string to `my.log`');

Console

The console log writes to process.stdout with pretty colors.

Console is the default transport, so the following are equivalent:

log = require('cedar')();
log = require('cedar')('color');

File

The file log writes JSON messages to a file. In addition, it acts as a simple event emitter so you can receive notifications when file rotation events occur.

var file = require('cedar')('file', {
  path: 'log/app_${YYYY}-${MM}-${DD}_${HH}:${NN}_${HOST}.log'
});
file.info('This will go into a file.');

var console = require('cedar')();

file.on('open', function (path) {
  console.log('Opened "' + path + '" for logging.');
});

file.on('close', function (path) {
  console.log('Closed "' + path + '".');
});

Multi

The multi log writes to multiple logs at once. Its configuration object is an array of configurations with transports specified by a transport property.

var log = require('cedar')([
  {transport: 'console'},
  {transport: 'file', level: 'info', path: 'log/app_${YYYY}-${MM}-${DD}_${HOST}.log'},
  {transport: 'file', level: 'error', path: 'log/${YYYY}/${MM}/${DD}/error_${HOST}.log'}
]);

More on Cedar...