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Node.js Application Configuration
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Runtime configuration for node.js deployment


node-config lets you apply a consistent pattern to module development making it easy to work with deployment configuration parameters.

As a module developer, node-config lets you define your parameters, then gets out of your way.

When running applications following this pattern, node-config lets you easily discover and set deployment-specific configuration parameters.


Configurations are defined at the top of your module. The following example is for a Customers module:

// Configuration parameters and default values
var config = require('config')('Customers', {
  dbHost: 'localhost',
  dbPort: 5984,
  dbName: 'customers',
  syncFrequency: 60       // Minutes between synchronizations

This gives you a config variable for your module, along with default values to use during development.

Use the config object anywhere in your module:

// Connect to the database
var dbConn = db.connect(config.dbHost, config.dbPort);

When running the application, you can specify module configuration overrides on the command line, or in a configuration file.

For example, the above dbHost value of the Customers module can be overridden on the command line, or in a config file.

Parameters specified on the command line:
$ node billing.js -Customers.dbHost smokin-db

Parameters specified in a configuration file:
$ node billing.js -config ./smokeTest.js

Any number of command line parameters and/or config files can be specified when running the application.

Installation & Testing

Node-config installs with npm and comes with an extensive suite of tests to make sure it performs well in your deployment environment.

To install and test node-config:

$ npm install config
$ npm test config

How It Works

When developing a module, use the following pattern for defining parameters and default values:

// Customers.js - Customer management utilities

// Configuration parameters and default values
var config = require('config')('Customers', {
  dbHost: 'localhost',
  dbPort: 5984,
  dbName: 'customers',
  syncFrequency: 60       // Minutes between synchronizations

When the application runs, node-config extends these default values with overrides from configuration files, followed by command line overrides, in the order they're specified on the command line.

Configuration Files

Configuration files let you define application deployment configurations in one place.

A configuration file is a JavaScript module that exports a single configuration object containing the modules, parameters, and values you want to override for your application.

The format of the object is best described by example smokeTest.js:

// Configuration overrides for smoke testing
module.exports = {
  'mod-sync': {
    remoteHost: 'smokin-sync',
    remotePort: 5984
  Customers: {
    dbHost: 'smokin-db',
    syncFrequency: 1

When running the app, you can specify this config file and additional parameters at the same time:

$ node billing.js -config smokeTest.js -Customers.dbPort 5985

This results in a config object in the Customers module with these values:

  dbHost: 'smokin-db',
  dbPort: 5985,
  dbName: 'customers',
  syncFrequency: 1

Advanced Usage

Programmatic configuration If you'd rather specify configuration files and parameter overrides in your application, just add the command line arguments programatically before the module is loaded.

// Always use port 5994 for the Customers service
process.argv.push('-Customers.dbPort', 5994);

Configuration discovery You can retrieve the current configuration for any module by omitting the second parameter, or all configurations by omitting all parameters to config.

// Load the Customer module parameters
var custConfig = require('config')('Customers');

// Load all application parameters
var allConfigs = require('config')();

Complex command line variables Variable names and values passed on through the command line can be strings, objects, or arrays.

$ node billing.js -Customers.custTemplate.region North
$ node billing.js -Customers.mailings[1] WelcomeMailing
$ node billing.js -Customers.mailingsSent [3,4,6]
$ node billing.js -Customers.homeOffice '{street:"4778 S. Main"}'

See Also

The node-monitor project is a good example of a module that makes use of the node-config module. It's also a pretty good way to monitor your running node.js application.


Released under the Apache License 2.0

See LICENSE file.

Copyright (c) 2010 Loren West

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