Node + Docker Hello World, for Showing Good Defaults for Using Node.js in Docker

This tries to be a "good defaults" example of using Node.js in Docker for local development and shipping to production with all the bells, whistles, and best practices. Issues/PR welcome.

Note I have courses on Docker, Swarm, and upcoming Docker for Node.js here.

Local Development Features

• Dev as close to prod as you can. docker-compose builds a local development image that is just like production image except for the below dev-only features needed in image. Goal is to have dev env be as close to test and prod as possible while still giving all the nice tools to make you a happy dev.
• Prevent needing node/npm on host. Installs node_modules outside app root in container so local development won't run into a problem of bind-mounting over it with local source code. This means it will run npm install once on container build and you don't need to run npm on host or on each docker run. It will re-run on build if you change package.json.
• One line startup. Uses docker-compose up for single-line build and run of local development server.
• Edit locally while code runs in container. docker-compose uses proper bind-mounts of host source code into container so you can edit locally while running code in Linux container.
• Use nodemon in container. docker-compose uses nodemon for development for auto-restarting node in container when you change files on host.
• Enable debug from host to container. opens the inspect port 9229 for using host-based debugging like chrome tools or VS Code. Nodemon enables --inspect by default in docker-compose.
• Provides VSCode debug configs and tasks for tests. for Visual Studio Code fans, .vscode directory has the goods, thanks to @JPLemelin.
• Small image and quick re-builds. COPY in package.json and run npm install before COPY in your source code. This saves big on build time and keep container lean.
• Bind-mount package.json. This allows adding packages in realtime without rebuilding images. e.g. dce node npm install --save <package name> (dosn't work on all systems)

Production-minded Features

• Use Docker build-in healthchecks. uses Dockerfile HEALTHCHECK with /healthz route to help Docker know if your container is running properly (example always returns 200, but you get the idea).
• Proper NODE_ENV use. Defaults to NODE_ENV=production in Dockerfile and overrides to development in docker-compose for local dev.
• Don't add dev dependencies into production image. Proper NODE_ENV use means dev dependencies won't be installed in container by default. Using docker-compose will build with them by default.
• Enables proper SIGTERM/SIGINT for graceful exit. Defaults to node index.js rather then npm for allowing graceful shutdown of node. npm doesn't pass SIGTERM/SIGINT properly (you can't ctrl-c when running docker run in foreground). To get node index.js to graceful exit, extra signal-catching code is needed. The Dockerfile and index.js document the options and links to known issues.
• Run node in the container as node user, not root.
• Use docker-stack.yml example for Docker Swarm deployments.

Assumptions

• You have Docker and Docker-Compose installed (Docker for Mac, Docker for Windows, get.docker.com and manual Compose installed for Linux).
• You want to use Docker for local development (i.e. never need to install node/npm on host) and have dev and prod Docker images be as close as possible.
• You don't want to lose fidelity in your dev workflow. You want a easy environment setup, using local editors, node debug/inspect, local code repo, while node server runs in a container.
• You use docker-compose for local development only (docker-compose was never intended to be a production deployment tool anyway).
• The docker-compose.yml is not meant for docker stack deploy in Docker Swarm, it's meant for happy local development. Use docker-stack.yml for Swarm.

Getting Started

If this was your Node.js app, to start local development you would:

• Running docker-compose up is all you need. It will:
• Build custom local image enabled for development (nodemon, NODE_ENV=development).
• Start container from that image with ports 80 and 9229 open (on localhost).
• Starts with nodemon to restart node on file change in host pwd.
• Mounts the pwd to the app dir in container.
• If you need other services like databases, just add to compose file and they'll be added to the custom Docker network for this app on up.
• Compose should detect if you need to rebuild due to changed package.json or Dockerfile, but docker-compose build works for manually building.
• Be sure to use docker-compose down to cleanup after your done dev'ing.

If you wanted to add a package while docker-compose was running your app:

• docker-compose exec -w /opt/node_app node npm install --save <package name>
• This installs it inside the running container.
• Nodemon will detect the change and restart.
• --save will add it to the package.json for next docker-compose build

To execute the unit-tests, you would:

• Execute docker-compose exec node npm test, It will:
• Run a process npm test in the container node.
• You can use the vscode to debug unit-tests with config Docker Test (Attach 9230 --inspect), It will:
  • Start a debugging process in the container and wait-for-debugger, this is done by vscode tasks
  • It will also kill previous debugging process if existing.

Ways to improve security

Run Node.js as Non-Root User

As mentioned in the official docker node image docs, Docker runs the image as root. This can pose a potential security issue.

• https://github.com/nodejs/docker-node/blob/master/docs/BestPractices.md#non-root-user

As a security best practice, it is recommended for node apps to listen on non-privileged ports as mentioned here:

• https://github.com/i0natan/nodebestpractices/blob/master/sections/security/non-root-user.md

Other Resources

• https://blog.hasura.io/an-exhaustive-guide-to-writing-dockerfiles-for-node-js-web-apps-bbee6bd2f3c4

MIT License,

Copyright (c) 2015-2019 Bret Fisher

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