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Designing for multiple environments

When running your application in different environments, like those provided by ReleaseHub, you may need to make some minor changes to your code to support multi-variations. You may need to adapt your code depending on how your framework handles CORS, or you may want to support frontends pointing to different instantiations of a backend. ReleaseHub provides several environment variables to use in your application to assist you to properly configure your application to work in multiple environments.
ReleaseHub provides the following environment variables:
  • RELEASE_ENV: set to true for all ReleaseHub environments
  • SERVICE_INGRESS_URL: where SERVICE is the name of your service, including https://
  • SERVICE_INGRESS_HOST: where SERVICE is the name of your service, no protocol added
  • RELEASE_RANDOMNESS: the random unique portion of the URL
For example, the following code configures CORS in Django:
"""
Django settings for backend project.
"""
import os
import re
import logging, logging.config
IS_RELEASE_ENV = bool(os.environ.get('RELEASE_ENV', None))
API_INGRESS_HOST = os.environ.get('API_INGRESS_HOST', '')
API_INGRESS_URL = os.environ.get('API_INGRESS_URL', '')
if DEBUG:
ALLOWED_HOSTS = ['*']
elif IS_RELEASE_ENV:
logger.info('RELEASE ENV: allowing ingress host: %s' % (API_INGRESS_HOST))
ALLOWED_HOSTS = [API_INGRESS_HOST]
else:
ALLOWED_HOSTS = ['example.com']
if IS_RELEASE_ENV:
BASE_RETURN_URL = API_INGRESS_URL
else:
BASE_RETURN_URL = 'https://example.com'

Applications with a frontend and backend

If your app uses a JavaScript framework, such as React, on the frontend, and Rails on the backend, you will need to configure the Rails backend to allow traffic from the frontend. You will also need to configure the frontend to talk to the backend.
In the following example, a Rails backend service named backend is configured to allow traffic from a React frontend service named frontend:
module MySweetApp
class Application < Rails::Application
frontend_ingress_host = ENV.fetch('FRONTEND_INGRESS_HOST') { "localhost:4000" }
# CORS
config.middleware.insert_before 0, Rack::Cors do
allow do
origins frontend_ingress_host
resource "*",
headers: :any,
methods: [:get, :post, :put, :patch, :delete, :options, :head],
credentials: true
end
end
end
end
ReleaseHub will generate the following environment variables to use in your application:
  • FRONTEND_INGRESS_URL
  • FRONTEND_INGRESS_HOST
  • BACKEND_INGRESS_URL
  • BACKEND_INGRESS_HOST
Now we need to configure the frontend service to talk to the backend. Here we configure Axios to talk to our backend:
import axios from "axios";
import config from "../config";
const client = axios.create({
baseURL: process.env.BACKEND_INGRESS_URL || "http://localhost:3000",
withCredentials: true,
headers: {
"Content-Type": "application/json"
}
});