stacklog

stacklog is a generic wrapper for logging modules that allows you to add log state to nested callbacks. It came about from a project that I recently shipped that required very detailed logging to debug. By "stacking" up logging prefixes, I was able to trace the application flow. The downside of this approach is that it requires discipline during development--each function entry must be logged. I used a few snippets in Vim to automate the process.

Note: stacklog does not pass the log prefix stack out of normal closure scope. If your code calls out to another module or function, it will log accordingly. A totally contrived example is below:

info: [FakeApp][run] User requested 123
info: [DAL][get] 123
info: [DAL][get][onGet] 123 retrieved
info: [FakeApp][run][onGetWidget] returning widget 123, name 'Foo'

Performance implications? Yes. Not logging at all performs much better (as expected). Short of using dTrace, this is an unavoidable penalty that any logging solution will have to incur. The upside is that running stacklog at less verbose log levels (as you would in normal production operation) performs better than leaving console.log() statements in.

If you find this useful, or you have a better way of accomplishing the same task, I would love to hear it!

@jdslatts on twitter or Justin@zeroarc.com

Example

Code

var winston = require('winston')
, StackLog = require('stacklog')
, log = (new StackLog(winston))('FakeApp')
;

;(function run() {
  log.info();

  log.info(null,'Logging an object with winston', {...Complex Object...})

  var l = log.info('run', 'I want a pony!');

  process.nextTick(function(){
    l.error('No!');
  });
})();

Output

info: [FakeApp]
info: [FakeApp] Logging an object with winston { Object Stringified }
info: [FakeApp][run] I want a pony!
error: [FakeApp][run] No!

Installation

$ npm install stacklog

How to use

Other than the minimal example above, stacklog is best used when abstracted away from your app in a local module. This will allow you to set up your preferred logger with appropriate config and then call it throughout your application. See examples/fakeapp.js and example/winston.js for a more realistic use case. To run the example (which uses Winston):

npm install winston
node examples/fakeapp.js

Options

By default, stacklog will wrap all stack entries in [square] brackets. To change to a different delimiter, pass an options object to the constructor:

new StackLog(logger, {bd: '(', ed: ')'});

Performance

Tests were run on core i7 2012 Macbook Air w/ 8GB ram. Average over 100 runs of 1000 iterations. There was zero sciences involved in this experiment.

Test - average (microseconds)

nolog.js - 1.8
console.js - 22041.17
winston.js - 45438.45
stacklogon.js - 77842.35
stacklogoff.js - 14706.28

License

(The MIT License)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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jslatts/stacklog