cedar v0.3.4
Cedar
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 supportscluster
, 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'}
]);
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