dockergen

The goal of this project is to create a simple Node package that is capable of creating customized Dockerfiles for Node projects and building the images associated with those Dockerfiles.

Features

• Generates Dockerfile based on a template with many configuration options.
• Configuration can be controlled directly by options in package.json.
• Support for "scopes" and private repositories.
• Support for yarn and using yarn.lock for deterministic deployments.

Installation

You can install dockergen either globally using npm install -g dockergen or as a dev dependency using npm install dockergen --dev. If installed as a dev dependency, the dockergen bin script will be in your PATH if running dockergen from NPM scripts via npm run ....

Usage

Pure command line

Generating Dockerfiles

All available options can be found via the --help option, e.g.,:

$ dockergen gen --help

Options:
  --help           Show help                                              [boolean]
  -i, --image      Base Docker image              [string] [default: "node:latest"]
  -e, --env        Settable environment variables (NAME=VAL)  [array] [default: []]
  -x, --expose     Ports to EXPOSE                            [array] [default: []]
  -s, --script     Scripts to run during build                [array] [default: []]
  -c, --scope      Scope to use for repos                  [string] [default: null]
  -o, --overwrite  Overwrite existing Dockerfile         [boolean] [default: false]
  -t, --test       Run tests during build                 [boolean] [default: true]
  -r, --runcmd     NPM script to launch application     [string] [default: "start"]

Building Docker images

Normally, one would use docker build -t <NAME> . to build a docker image from an existing Dockerfile. But because we want to supporting building using private repositories AND doing so as part of the build process (as opposed to installing Node packages when the container is start), we need to add some build arguments. The typical build command would look something like:

docker build --build-arg NPM_TOKEN=00000000-0000-0000-0000-000000000000 -t <NAME> .

To help streamline this, the dockergen script features an additional build command that adds these extra command line arguments. The equivalent dockergen command would be:

$ dockergen build --name <NAME>

The token is taken from the environment variable NPM_TOKEN to avoid having to hardwire it into any files that might be version controlled or otherwise shared with others.

The command line arguments for dockergen build are:

$ dockergen build --help

Options:
  --help        Show help                                                 [boolean]
  -n, --name    Name to give image being built  [string] [required] [default: null]
  -k, --dryrun  Perform a dryrun build                   [boolean] [default: false]
  -d, --docker  Docker command                         [string] [default: "docker"]

Using npm run

As mentioned previous, if dockergen is installed as a dev dependency, it can be called via npm run .... An example of using dockergen from the scripts section of package.json might look like this:

  "scripts": {
    ...
    "gen": "dockergen gen",
    "image": "dockergen build",
  }

Note the absence of any command line switches? Such switches can be avoided by building them directly into package.json. By default, dockergen looks for a "dockergen" section in package.json. Any fields in that object are used as the default values for the command line arguments (note that env is a special case...it appears as an object in package.json but as an array of strings of the form <NAME>=<VAL> when specified via the command line).

N.B. if you want to check that dockergen is picking up default values from package.json, simply run dockergen gen --help. The default values shown by --help include any values found in package.json.

Use with sdocker

Note that dockergen build includes a command line option --docker. This allows you to use an alternative program as the Docker client. For example, you can substitute sdocker (an alternative client that supports SSH tunneling) using this option. This allows you to avoid the complication of using TLS certificates for secure use of Docker and instead rely on SSH keys.