Andrey Mikhaylov

Andrey Mikhaylov @lolmaus

frontend developer, EmberJS enthusiast
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Do not confuse environment for deploy target

18th February 2017 (last updated at 24th December 2017)

Most frameworks have a concept of environment. Many developers are misusing it as a deploy target.

This article was originally posted on Deveo blog.

When Deveo was acquired by Perforce, Deveo blog was turned down.

I'm seeing the term environment used as a synonym of deploy target all the time. I believe, it causes a lot of confusion, and I would like clear it up.

This article is written with the EmberJS frontend framework in mind, but the idea is applicable to any other web framework, both frontend and backend.

There are many articles on the web that may seem to contradict to what I'm gonna say, especially if you skim them without giving them deep consideration. Those articles have been frustrating to me for a long time, until I figured that the problem is that terminology is confusing.

In EmberJS and many other web frameworks the term environment is used in a narrow meaning, and I'm gonna use this very meaning below. Environment is a collection of parameters that configure how your wep app is built and run, such as:

  • code minification,
  • asset fingerprinting/cache busting,
  • source map generation,
  • various debugging tools,
  • testing,
  • applying code coverage markers,
  • removing test selectors from HTML.

There is another category of parameters, that is commonly referenced as environment. I believe that's a terrible mistake, and the second category must be distinguished from environment.

I call it deploy target. It includes the following params:

  • API URLs,
  • CDN URLs,
  • CSP/CORS configuration,
  • API keys.

Many developers put those two categories of params into one pile and make them depend on the environment variable, which in most frameworks can have one of three values: development, production and test.

As a result, the app essentially has only two modes:

  • production build to production server,
  • development build to development server.

A necessity to deploy a development build to a production server is not rare. You typically need that to debug a problem that only manifestates on the server and can't be reproduced locally.

The opposite is also sometimes necessary: to make a production build against a local server. It can help you to benchmark your app's performance or to debug a problem with minification/fingerprinting.

When you have your environment and deploy target hard-wired, the only way to decouple them is to edit your configuration files by hand, make the unusual build, then undo your changes and make sure you don't accidentally commit them.

The worst part is that API keys are typically stored in your VCS, which is a security issue.

I recommend you to use dotenv files.

Dotenv files are configuration files with names that start with .env- prefix. They store environment variable definitions as key=value pairs, one per line:


Your app will read one of those files during build and use its values.

The phrase "environment variables" contributes to confusion, be careful. "Environment variables" are variables that you can pass from command line.

Here's what you should do:

  1. Remove all deploy target parameters from your code.
  2. Move them into dotenv files. Make one dotnev file per deploy target. For example, .env-production, .env-staging, .env-sandbox, .env-local, .env-mock, etc. You can have as many as you need, not just production and development.
  3. It is crucial that you gitigonre your dotenv files, so that your API keys do not get exposed through version control.
  4. If you're using CI, you can copy variables from your dotenv files to your CI's online configuration. For example, the corresponding settings section in CodeShip is called "deployment pipelines".
  5. Set up your app to accept a deploy target param, read the corresponding dotenv file and use values inside it. Most platforms have a dotenv library to do that.

You're now able to select a deploy target separately from environment.

For example, when I need to run a produciton build against a local server I can do:

DEPLOY_TARGET=local ember serve --environment=production

Of course, you can configure your app in such a way that a certain default deploy target is automatically selected for every environment. This will let you avoid redundancy in most common combinations.

You may object: we've come a full circle and now we are where we started: envrionment and deploy target are coupled. What's the point?

Yes, it is like that by default: your app will use development environment for local builds and production environment for deployments to production servers. But now you can override them and use any combination of environments and deploy tarets — without a need to modify your code and then roll back.

The dotenv npm library can be used in Ember directly. But if you need to access your deploy target params both in ember-cli-build.js and config/environment.js, or in FastBoot, then you should use the ember-cli-dotenv addon.

Create .env- files in the root folder of your Ember CLI project, one per each backend you're using, including local and mock servers if you use them:


A top-notch technique is to give your servers personal names. Using .env-linode1 instead of .env-production will make things more clear.

Put deploy target configuration into each file like this:


Some of params may be shared across servers, that's fine.

You are recommended to prefix your variable names with your app name in order to prevent collisions with external env vars that you may also need.

No we need to teach ember-cli-dotenv load a specific dotenv file depending on our needs. Use this trick in your config/environment.js file:

const fs = require('fs')

const environment   = process.env.EMBER_ENV || 'development'
const defaultTarget = environment === 'production' ? 'production' : 'localhost-4200'
const target        = process.env.DEPLOY_TARGET || defaultTarget
const dotEnvFile    = `./.env-${target}`

if (fs.existsSync(dotEnvFile))`using dotenv file: ${dotEnvFile}`)
else console.warn(`dot-env file not found: ${dotEnvFile}, assuming env vars are passed manually`)

module.exports = function (env) {
  return {
    clientAllowedKeys : [
    path : dotEnvFile,

This will make the params from a given dotenv-file appear in the process.env hash, which in turn is available in config/environment.js and ember-cli-build.js. Use it like this:

  gitHubApiKey: process.env.MYAPP_GITHUB_API_KEY

Instead of accessing the config/environment.js in your app directly, create a config Ember service that will proxy the values from config/environment.js. Not only this will improve your app's architecture, it will also allow you have global computed properties derived from values read from config/environment.js.

The above code will use production deploy target in the production environment and localhost-4200 in development. You should adjust deploy target names used in the code by default.

ember s -prod   # uses `production` environment with `production` deploy target
ember s         # uses `development` environment with `localhost-4200` deploy target

Here's how you can tell which dotenv file to use:

DEPLOY_TARGET=localhost-4200 ember s -prod   # uses `production` environment with `localhost-4200` deploy target
DEPLOY_TARGET=production ember s             # uses `development` environment with `production` deploy target

ember-cli-deploy has built-in support for dotenv files, but they're used only for ember deploy commands, whereas ember-cli-dotenv can be used both with ember deploy and default commands like ember serve, ember build, ember test, etc.

There are a number of gotchas you have to be aware of when you use ember-cli-dotenv together with ember-cli-deploy.

First of all, ember-cli-deploy docs use the phrase "build environment" as a synonym for deploy targets, which contributes to confusion.

Secondly, the config/deploy.js configuration file lets you define configuration based on deploy target. Rename deploy target names in the file to match the ones in your dotenv file names.

Thirdly, don't use short names like dev and prod. Use full names development and production or, even better, use unique names for your servers.

Fourthly, mind that ember-cli-deploy also uses the DEPLOY_TARGET env var. But for some reason it can't be used like this:

DEPLOY_TARGET=production ember deploy

Instead, you're supposed to write

ember deploy production

The trouble is that the config/dotenv.js files kicks in earlier than the ember deploy production command sets environment to production and assigns it to the DEPLOY_TARGET env var.

One solution is to pass the DEPLOY_TARGET variable explicitly for your config/dotenv.js to use:

DEPLOY_TARGET=production ember deploy production

But this command is quite bulky. You can avoid the redundancy by teaching your config/dotenv.js to be aware of the ember deploy production command:

const fs = require('fs')

function getDeployTarget () {
  return process.env.DEPLOY_TARGET || getDefaultDeployTarget()

function getDefaultDeployTarget () {
  const environment =
    || deployEnv()
    || 'development'

  return environment === 'production' ? 'production' : 'localhost-4200'

function deployEnv () {
  if (process.argv[2] === 'deploy' && process.argv[3] === 'prod') {
    throw new Error("Command `ember deploy prod` is not supported. Please use `ember deploy production`.")
  } else if (process.argv[2] === 'deploy' && process.argv[3] === 'production') {
    return 'production'

const dotEnvFile   = `./.env-${getDeployTarget()}`

if (fs.existsSync(dotEnvFile))`Using dotenv file: ${dotEnvFile}`)
else console.warn(`dot-env file not found: ${dotEnvFile}, assuming env vars are passed manually`)

module.exports = function (env) {
  return {
    clientAllowedKeys : [
    path : dotEnvFile,

As a result, the ember deploy production command will use the .env-production dotenv file and set the environment to production.

When you need to deploy a development build (e. g. with no minification) to production, use this command:

EMBER_ENV=development ember deploy production

Don't hesitate to share what you have to say in the comments!