Rails 5+, WebPacker and Docker development workflow

Question

One of the advantages of using Docker is single environment for entire team. Some time ago I was using Vagrant to unify development environment in a team, and it worked pretty well. Our workflow was like:

• Run vagrant up, command takes some time to download the base image, run provisioning scripts. It also maps directory from local filesystem to container filesystem.

• Change file on the host system, all changes will be mapped to guest filesystem (container), so no container restart needed.

Some folks use Docker for the similar development workflow, but I usually use docker-compose just to run satellite services. And I was always running Rails monolith inside of host operating system, like natively.

So my development workflow is pretty standard:

• All the satellite services are up and located inside of Docker containers, I just have a bunch of exposed ports. I don't need to brew-install lots of software to support them, it's good.

• Rails monolith runs in host OS, so every time I make, for example, JavaScript file change, WebPacker comes into play, rebuilds, and applies changes without page refresh. It's important to emphasize, because page refresh takes time, I don't want to refresh the page every time I do JavaScript or CSS file change.

With Vagrant the above scheme works well as well. But with Docker things are different.

The development workflow some folks use with Docker is as follows:

• Run a bunch of services with docker-compose command, except Rails monolith (same step as with my development workflow above).

• Every time you make change in your app (for example, JavaScript file) you need to rebuild container, because you're making changes on your local filesystem, not inside of a docker container. So you 1) stop 2) build 3) run Docker container again.

In other words, with Docker-only approach we have the following cons:

• No webpacker js/css refresh
• Container rebuild, which takes time
• Application restart, which takes a lot sometimes, even zero-code "Rails" app starts in ~3 seconds

So my question is: what's the best way to go with Docker-only approach? How you can take advantage of Docker while using WebPacker with Rails and avoid page refresh and application restart?

Answer 1

I've been reading a good book on this recently (Docker for Rails developers). The gist seems to be that you run Rails in a Docker container and use a volume to 'link' your local files into the container, so that any file changes will take immediate effect. With that, you should not need to restart/rebuild the container. On top of that, you should run webpack-dev-server as a separate container (which also needs the local files mounted as a volume) which will do JavaScript hot reloading - so no need to reload the page to see JS updates.

Your docker-compose.yml file would look something like this (uses Redis and Postgres as well):

version: '3'

services:
  web:
    build: .
    ports: 
      - "3000:3000"
    volumes: 
      - .:/usr/src/app
    env_file:
      - .env/development/web
      - .env/development/database
    environment:
      - WEBPACKER_DEV_SERVER_HOST=webpack_dev_server
  webpack_dev_server:
    build: .
    command: ./bin/webpack-dev-server
    ports:
      - 3035:3035
    volumes:
      - .:/usr/src/app
    env_file:
      - .env/development/web
      - .env/development/database
    environment:
      - WEBPACKER_DEV_SERVER_HOST=0.0.0.0
  redis:
    image: redis
  database:
    image: postgres
    env_file:
      - .env/development/database
    volumes:
      - db_data:/var/lib/postgresql/data
volumes:
  db_data: