sample node app for Docker examples
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README.md

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.

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.
  • 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 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.

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

Other Resources

MIT License,

Copyright (c) 2015-2018 Bret Fisher

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.