simple-console-logger

Console Logger

A simple, light-weight and fast console logger that uses speed-date for fast timestamps. Ideal for production if you're using PM2 to manage logs via stdout and you don't need log file management or other appenders. Category logging was designed to be the same as log4js-node.

Features:

• Simple configuration via options or an external JSON file
• Option to watch the external config file for dynamic re-configuration
• Uses same levels and ability to use categories as log4js-node
• Configurable timestamps that can be turned off in production if using PM2 to generate timestamps (this increases performance significantly).
• Works in browser for selectively debugging via the console.

Usage:

Directly using the default logger:

var log = require('simple-console-logger')

log.info('Hello %s', 'World')

// output - default level is info
2/17/2016 8:30:33 AM: INFO: Hello World

Using category loggers:

var logger = require('simple-console-logger')

logger.configure({level: 'debug'})

var log = logger.getLog()  // default logger
var log1 = logger.getLog('category1')  // category loggers
var log2 = logger.getLog('category2')  
var log3 = logger.getLog('category3')  

log.info('Hello %s', 'World')
log1.info('An info message from category1')
log2.debug('A debug message from category2')
log3.trace('A trace message from category3 will not be logged')

// output
2/17/2016 8:30:33 AM: INFO: Hello World
2/17/2016 8:30:33 AM: INFO: category1: An info message from category1
2/17/2016 8:30:33 AM: DEBUG: category2: A debug message from category2

If logging is already configured in main module, other modules can just do:

const log = require('simple-console-logger').getLogger('MyModule');

NOTE: If using in the browser for console debugging all file configuration is disabled, just pass logging options to the configure method.

Configuration Options

For Version 2.x

Due to issues with running in the browser and Webpack/dynamic requires, the logger no longer requires the fs module and does not automatically look for a default logconfig.json file. In order to configure the logger from an external file, do so like this:

const logger = require('simple-console-logger');
const fs = require('fs');

logger.configure('./logconfig.json', fs);

For Version 1.x

The logger can be configured via options passed to the config method. If you skip the config step but the logger finds the file ./logconfig.json it will read the configuration from there. If not configured the level defaults to INFO for all loggers. You can also pass a configuration object or the full path to a logging config file. If either the default or specified configuration file is used, a watch option can be enabled to dynamically change levels. If NODE_ENV is production the configuration file is checked for changes every watchInterval seconds (default is 60, minimum is 10). If in development mode fs.watch is used.

Options

• level The log level for all loggers. Defaults to INFO. NOTE: that level strings are case insensitive but are always printed uppercase.
• levels Allows per-category levels to be specified just as in log4js-node. Note that the "[all]" category is supported to be compatible with Log4js, but this is the exact same thing as setting the level option above. If you set both, the [all] category will override.
• watch If configured via an external JSON file you can set watch to true to watch for changes and dynamically change the configuration. Default is false.
• watchInterval The time in seconds to check for configuration file changes if watch is true. Defaults to 60 seconds. The minimum value that supported is 10 seconds.
• dateFormat Optional function to format timestamps. This is passed to speed-date. To disable timestamps (for example if using PM2 to generate log timestamps) set this option to null. If not explicitely set the default timestamp format will be YYYY-MM-DD HH:mm:ssZ.

Example:

var logger = require('consolelogger')

logger.config({
    level: 'info', // default level
    levels: {
        category1: 'debug',
        category2: 'info',
        category3: 'error'
    },
    dateFormat: 'YYYY-MM-DD HH:mm:ssZ',
    watch: false
})

// ... enable watching, using [all] category rather than level, remove timezone offset:

logger.config({
    levels: {
        '[all]': 'INFO'
        category1: 'DEBUG',
        category2: 'ERROR',
        category3: 'TRACE'
    },
    dateFormat: 'YYYY-MM-DD HH:mm:ss',
    watch: true,
    watchInterval: 10
})

Performance

Running a test to log 1 million lines:

[~] $ time node logtest.js | dd > out

1045+707624 records in
204861+1 records out
104888910 bytes transferred in 6.096642 secs (17204374 bytes/sec)

real	0m6.111s
user	0m5.286s
sys	0m2.640s

Running the same test using log4js with single console appender:

[~] $ time node logtest.js | dd > out

540+993360 records in
241970+1 records out
123888911 bytes transferred in 19.298922 secs (6419473 bytes/sec)

real	0m19.318s
user	0m18.282s
sys	0m3.513s