Docker: Best practice for development and production environment

Question

Suppeose I have a simple node.js app. I can build a container to run the app with a simple Dockerfile like this:

FROM ubuntu:16.04
RUN apt-get update && apt-get install -y nodejs nodejs-legacy npm
COPY . /app
WORKDIR /app
RUN npm install
CMD node index.js

This will copy the source code into the container and I can ship it off to a registry no problem.

But for development I don't want to rebuild the container for every change in my code. So naturally, I use a volume in combination to nodemon. Here's my questions:

• How do I keep the different configurations? Two dockerfiles? Use compose with two different compose files?
• The node_nodules folder on my host is different from the one I need in the container (i.e. some packages are installed globally on the host). Can I exclude it from the volume? If so, I need to run npm install after mounting the volume. How do I do this?

So my question is really: How do I keep dev and deploy environments separate. Two Dockerfiles? Two compose-files? Are there any best practices?

Answer 1

So the way I handle it is I have 2 Docker files (Dockerfile and Dockerfile.dev).

In the Dockerfile.dev I have:

FROM node:6

# Update the repository
RUN apt-get update

# useful tools if need to ssh in or used by other tools
RUN apt-get install -y curl net-tools jq

# app location
ENV ROOT /usr/src/app

COPY package.json /usr/src/app/

# copy over private npm repo access file
ADD .npmrc /usr/src/app/.npmrc

# set working directory
WORKDIR ${ROOT}

# install packages
RUN npm install

# copy all other files over
COPY . ${ROOT}

# start it up
CMD [ "npm", "run", "start" ]

# what port should I have
EXPOSE 3000

My NPM scripts look like this

"scripts": {
    ....
    "start": "node_modules/.bin/supervisor -e js,json --watch './src/' --no-restart-on error ./index.js",
    "start-production": "node index.js",
    ....
},

You will notice it uses supervisor for start so any changes to any file under src will cause it to restart the server without requiring a restart to docker.

Last is the docker compose.

dev:
  build: .
  dockerfile: Dockerfile.dev
  volumes:
    - "./src:/usr/src/app/src"
    - "./node_modules:/usr/src/node_modules"
  ports:
    - "3000:3000"

prod:
  build: .
  dockerfile: Dockerfile
  ports:
    - "3000:3000"

So you see in a dev mode it loads and mounts the current directory's src folder to the container at /usr/src/app/src and also the node_modules directory to the /usr/src/node_modules.

This makes it so that I can make changes locally and save, the volume will update the container's file, then supervisor will see that change and restart the server.

** Note as it doesn't watch the node_modules folder you have to change another file in the src directory to do the restart **

Answer 2

Use environment variables. See the documentation Docker env. This is the recommended way, also for use in the production.