12factor-config

Read the config for your app from only the environment.

12factor-config

A config module which only reads the environment. For Node.js that means process.env.

We will not ever use NODE_ENV in any example here since each environment should specify everything it needs and nothing should be dependent on being a particular environment (such as 'development', 'testing', 'staging' or 'production').

Firstly, set some environment variables that your program will look for. You don't need to set any that have a 'default' but you do need to set any that are 'required'.

$ export REDIS_URL=redis://user:password@hostname:port/db
$ export APPNAME_PORT=8080

Then, in your program:

var config = require('12factor-config');
 
var cfg = config({
    redisUrl : {
        env      : 'REDIS_URL',
        type     : 'string', // default 
        required : true,
    },
    logfile : {
        env      : 'APPNAME_LOG_FILE',
        type     : 'string',
        default  : '/var/log/appname.log',
        required : true,
    },
    port : {
        env      : 'APPNAME_PORT',
        type     : 'integer',
        default  : '8000',
        required : true,
    },
    debug : {
        env      : 'APPNAME_DEBUG',
        type     : 'boolean',
        default  : false,
    },
    env : {
        env      : 'NODE_ENV',
        type     : 'enum',
        values   : [ 'development', 'test', 'stage', 'production', ],
    },
});
 
console.log(cfg);

Should output something like:

{
  redisUrl: 'redis://user:password@hostname:port/db',
  logfile: '/var/log/appname.log',
  port: 8080,
  debug: false,
  env: 'development'
  }

It is advisable to prefix your environment variables with a prefix related to your application name as shown in the later config vars above. Mainly this is to namespace your vars and not stomp over others already defined. Of course you don't need to use the prefix in the local name.

I usually have a lib/cfg.js such as the following:

var config = require('12factor-config');
 
var cfg = config({
    // ... environment config here ... 
});
 
module.exports = cfg;

By doing this, all other files in your application can just require('lib/cfg.js') and obtain the exact same configuration.

Written by Andrew Chilton - Blog - Twitter.

MIT - http://chilts.mit-license.org/2013/

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