Tools for debugging your node.js modules and event loop


Diagnostics provides a set of tools that is designed to help you with debugging your Node.js and front-end applications.

npm install --save diagnostics

We're starting out small but every major release will unlock another piece of the puzzle. The following tools are already at your disposal:

Logging is something you always need in your applications, if you don't know what's going on, it's damn hard to fix it. This is especially true with async systems when your stack traces are most likely completely useless. In diagnostics we ship a simple logger which can be turned on and off using environment variables. So it's out of the way for your users and there when you need it.

The logger is exposed as function:

var log = require('diagnostics')('example');
log('foo %s', 'bar');

The first argument in the function is the namespace of you log function. All log message will be prefixed with. But we also allow a second argument. This can be used to configure the logger. The following options can be configured:

  • color: The color for the namespace, this can be a hex (#FFF) color string or the name of a color. If no color is provided we will generate consistently hashed color from the given namespace and use that instead.
  • color**s**: Forcefully enable or disable the use of colors in the log output. If no colors boolean is provided we will determine if it's a proper tty and show colors.
  • stream: The stream instance we should write our logs to. We default to process.stdout (unless you change the default using the .to method).
  • precise: By default our log timing is rounded up to the nearest number. If you need more precise timing you can set this option to true.

The beauty of this logger is that it allows a custom stream where you can write the data to. So you can just log it all to a separate server, database and what not. But we don't just allow one stream we allow multiple streams so you might want to log to disk AND just output it in your terminal. The only thing you need to do is either use:


To set multiple streams as the default streams or supply an array for the logger it self:

var log = require('diagnostics')('example', { stream: [

In addition to using the DEBUG environment variable you can also the DIAGNOSTICS environment variable.