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Caterpillar is the ultimate logging system for Node.js, based on transform streams you can log to it and pipe the output off to different locations, including some pre-made ones. Caterpillar also supports log levels according to the RFC standard, as well as line, method, and file fetching for messages.
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README.md

Caterpillar

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Caterpillar is the ultimate logging system for Node.js, based on transform streams you can log to it and pipe the output off to different locations, including some pre-made ones. Caterpillar also supports log levels according to the RFC standard, as well as line, method, and file fetching for messages. You can even use it in web browsers with the Browser Transform.

Install

Backend

  1. Install Node.js
  2. npm install --save caterpillar

Frontend

  1. See Browserify

Usage

Example with the Filter and Human transforms

// Import
var level  = process.argv.indexOf('-d') === -1 ? 6 : 7;
var logger = new (require('./').Logger)({level:level});
var filter = new (require('caterpillar-filter').Filter)();
var human  = new (require('caterpillar-human').Human)();

// Pipe logger output to filter, then filter output to stdout
logger.pipe(filter).pipe(human).pipe(process.stdout);

// If we are debugging, then write the original logger data to debug.log
if ( level === 7 ) {
    logger.pipe(require('fs').createWriteStream('./debug.log'));
}

// Log messages
logger.log('emergency', 'this is level 0');
logger.log('emerg', 'this is level 0');
logger.log('alert', 'this is level 1');
logger.log('critical', 'this is level 2');
logger.log('crit', 'this is level 2');
logger.log('error', 'this is level 3');
logger.log('err', 'this is level 3');
logger.log('warning', 'this is level 4');
logger.log('warn', 'this is level 4');
logger.log('notice', 'this is level 5');
logger.log('note', 'this is level 5');
logger.log('info', 'this is level 6');
logger.log('default', 'this is level 6');
logger.log('debug', 'this is level 7');
logger.log('this is level 6, the default level');
logger.log('you','can','also','use','as','many','arguments','as','you','want',1,[2,3],{four:5});

Result with log level 6 (info):

Result with log level 7 (debug):

Transform API, extends stream.Transform

new (require('caterpillar').Transform)(config)
  • Methods
    • constructor(config?) create our new instance with the config, config is optional
    • pipe(child) pipe our stream to the child, also sync our config to it
    • setConfig(config) set the configuration and emit the config event
    • getConfig() get the configuration
    • format(entry) format the caterpillar logger entry
  • Configuration
    • none by default
  • Events
    • config(config) emitted once our configuration has updated

Logger API, extends Transform API

new (require('caterpillar').Logger)(config)
  • Methods

    • constructor(config?) create our new instance with the config, config is optional
    • log(args...) write a log message, the first argument is suppose to be the level (will use the default level if it isn't)
    • format(level, args...) create a log entry ready for writing to the logger stream, output is as follows:

      {
          "args": ["this is emergency and is level 0"],
          "date": "2013-04-25T10:18:25.722Z",
          "levelNumber": 0,
          "levelName": "emergency",
          "line": "59",
          "method": "Task.fn",
          "file": "/Users/balupton/Projects/caterpillar/out/test/caterpillar-test.js"
      }
    • getLevelNumber(name) get the level number for the level name

    • getLevelName(number) get the level name for the level number
    • getLevelInfo(nameOrNumber) get the level name and number for either a level name or number
    • getLineInfo() get the file, method, and line that the log method was called on
  • Configuration

    • lineOffset the amount of lines to offset when doing our line detection, useful for wrappers, defaults to 0
    • levels the level names and their associated number, also includes default for when no level was specified, defaults to:

      {
          emergency: 0,
          alert: 1,
          critical: 2,
          error: 3,
          warning: 4,
          notice: 5,
          info: 6,
          debug: 7,
      
          emerg: 0,
          crit: 2,
          err: 3,
          warn: 4,
          note: 5,
      
          default: 6
      }
  • Events

    • only those inherited

History

You can discover the history inside the History.md file

License

Licensed under the incredibly permissive MIT License
Copyright © 2012+ Bevry Pty Ltd
Copyright © 2011 Benjamin Lupton

Thanks

Uses the following:

  • RFC3164 for the level codes and names

Inspired by the following:

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