Environment variables

There are two ways of passing in environment variables to your applications/tests: Either throug the actual environment variables of the system Cantara is running on or through .env files.

Passing in environment variables through directly from the system is usally used in CI environments, whereas the use case of .env files is primarily in development environments, but that depends on your workflow.

Adding a new environment variable

The first step when adding a new environment variable is adding a new entry in the env array of the app's cantara.config.js. Go to the cantara.config.js file of the app/package where the environment variable is needed. If there is no cantara.config.js, create a new one. It could look like that:

module.exports = {
env: ['MY_ENV_VAR'],

Usually when adding environment variables to packages it's just because they are needed during tests.

By adding MY_ENV_VAR to this array, Cantara now knows that MY_ENV_VAR must be defined during execution and can warn the developer if that's not the case.

Using .env files

Now, in the application folder create a new file called .env.development and add the folllowing content:


When you now start the development of your app using the dev command, the value of process.env.MY_ENV_VAR will be env_var_value123. When executing the test or e2e command, Cantara will look if there is a file called .env.test in the app's folder. If not, it will fall back to .env. For building/deploying, Cantara will look for a file called .env.production.

Project wide .env files

If some env var values are needed in multiple applications, e.g. in two NodeJS APIs, you can create a .env.<stage> file in the project's root. This way, you don't need to define the env variable value twice.

Defining environment variables manually

Instead of creating those files, you can also define the environment variabled yourself by setting them in the current environment, e.g. your CI server. You need to prefix them, for example: If your CI system wants to run the build command for one of your apps and there's a environment variable called MY_ENV_VAR required, define it by prefixing it with PRODUCTION_, this PRODUCTION_MY_ENV_VAR. This can also be done for the testing environment by setting TEST_MY_ENV_VAR.

The --stage parameter

By appending the --stage parameter to any Cantara command, you can explicitly define which .env file or which environment variables from the system should be used. For example if you execute ctra dev my-app --stage production the .env.production file will be used. You can also create custom stages, e.g. .env.staging and execute commands using those stages, e.g. ctra build --stage staging. This can be useful if you have other environments then just your local development environemnt and the production environment, e.g. a staging server.

Optional Environment Variables

By default cantara replaces all environment variables, specified in the cantara.config.js, with there value on build time. While this is a desierable behavior for frontend code, in nodejs applications running on a server, it may be expected to read environment varialbes on runtime direclty form the server environment.

To aceive this it is possible to mark environment varialbes as optional:

module.exports = {
env: [{ var: 'MY_ENV_VAR', optional: true }],

This way cantara will replace the environment variable if it is defined on build (i.e. during development), but will leave it as is, if it is not defined (i.e. for production).

Setting Evironment Variables Directly in Configuration

In some rare use cases it might not be possible to define environment varialbes in the .env files, but the values must be computed at build time. In this cases the value can be directly injected in the cantara.config.js. A common use case for this is the injection of the version from the package.json :

const pkg = require('./package.json');
module.exports = {
env: [{ var: 'VERSION', value: pkg.version }],