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Welcome to Log Magic.

This project is usable. It doesn't do everything it should, yet.

The goal is to have a fast and easy to use logging subsystem that can be dynamically reconfigured to provide insight into production systems.

Logmagic does its magic by generating objects with generated functions that are only modified when the logging system is reconfigured, thus your entire logging path is contained within long-lived functions that V8 is able to JIT.

Getting Started

If you had a file named like, 'lib/foo/bar.js', at the top of it, you would put the following:

var log = require('logmagic').local('');

Then inside bar.js, you would just use the logger like any normal logger:'Hello!')
log.error('By default, format strings are not used.', {SOME_VAR: 'myvalue'})
log.errorf('Just add 'f' to any log method, and you get format strings too: ${SOME_VAR}', {SOME_VAR: 'myvalue'})

In any other part of your application, you can reconfigure the logging subsystem at runtime, making it easy to change log levels for specific modules dynamically.

/* Register an ad-hoc sink */
var logmagic = require('logmagic');
logmagic.registerSink('ad-hoc', function(module, level, message) { console.log(message); });

/* Send Info an higher in the root logger to stdout */
logmagic.route('__root__', logmagic.INFO, 'console')

/* Reconfigure all children of mylib to log all debug messages to your custom sink */
logmagic.route('mylib.*', logmagic.DEBUG, 'ad-hoc')


Sink modules should have this interface

  /* the log message callback */
  callback: function(modulename, level, message, obj) {}

  /* sets options for sink */
  setOptions: function(options) {}

  /* dispose of resources */
  dispose: function() {}

Registering a sink instance verbosely

var fileLog = new logmagic.sinks.File({filename: '/var/log/myapp.log'});
logmagic.registerSink('main', fileLog);

Registering the easy way for Console, File and Recipients

logmagic.registerFileSink('fileLog', '/var/log/myapp.log');
logmagic.registerConsoleSink('console', 'dark');

Setting options on a sink instance

logmagic.setSinkOptions('console', {plain: true});
logmagic.setSinkOptions('console', {scheme: 'light'});

Routing to multiple sinks

logmagic.registerRecipientsSink('multi', ['fileLog', 'console']);
logmagic.route('__root__', logmagic.INFO, 'multi')

Pre-registered sinks

  • console
  • grayLog2-stderr

Built-in sinks

  • Console: Logs to console with colors (may be disabled)
  • GrayLog2: Graylog2-style JSON to stderr
  • File: log to a file
  • Recipients: log to multiple registered sinks

See tests/t.js for an example.