Overview

This module provides a simple interface to your application's JSON configuration file on disk. It will load and parse the file, and can automatically reload it when it changes (and emit an event when this happens). Command-line arguments are automatically merged in with your config (uses pixl-args), and treated as overrides. The library also provides an easy way to determine the server's hostname and local IP address.

Usage

Use npm to install the module:

npm install pixl-config

Then use require() to load it in your code:

var Config = require('pixl-config');

To use the module, instantiate an object:

var config = new Config('conf/config.json');

If there is an error loading or parsing the file, an exception will be thrown, so you might want to wrap it in a try/catch.

Upon success, you can access your configuration keys/values using the get() method:

var verbose = config.get('verbose');
var debug = config.get('debug');

If you just want a hash of the entire config file, call get() without passing a key:

var opts = config.get();
if (opts.verbose) console.log("Verbose option is set.");
if (opts.debug) console.log("Debug option is set.");

You can also set values by calling set() and passing both a key and a value. Example:

config.set('verbose', true);

Values you set manually are persisted as long as the Node process is alive, even if the configuration file is reloaded on disk.

Command-line Arguments

Command-line arguments (from process.argv) are automatically parsed and merged in with your configuration, and treated as overrides. Only --key value --key value style arguments are processed.

Please see the pixl-args module for more details.

Live File Reloading

If you want the library to monitor your configuration file for live changes and automatically reload it, pass true as a second argument to the constructor:

var config = new Config('conf/config.json', true);

This uses polling, and by default it checks the file for changes every 10 seconds. The library then reloads the configuration and fires off an event you can listen for:

var config = new Config('conf/config.json', true);

config.on('reload', function() {
	console.log("My app's config was reloaded!");
	console.log("Verbose = " + config.get('verbose'));
} );

If there is an error reloading the configuration, an error event is emitted (no exception is thrown).

To set the polling frequency, pass in the desired number of milliseconds instead of true as the second argument. For example, to check every five seconds pass in 5000:

var config = new Config('conf/config.json', 5000);

To stop monitoring (for example during your app's shutdown sequence) call the stop() method.

If you would prefer to control exactly when to check for changes, do not enable live monitoring, and instead simply call the check() method at any frequency you want.

Server Environment

The library also provides a utility method for determining the server's hostname and IP address (IPv4). These things may require asynchronous operations, so you must specify a callback function. Upon completion, the hostname will be accessible via config.hostname and the IP address in config.ip (IPv4 dot-delimited string). Example:

config.getEnv( function() {
	console.log("The server hostname is: " + config.hostname);
	console.log("The server IP is: " + config.ip);
} );

License

The MIT License

Copyright (c) 2014 - 2019 by Joseph Huckaby

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.