ddsl

Docker Declarative Specific Language

ddsl allow developers to express in a declarative way how application are built, run and tested. Building, running and testing applications should be semlessly, independently on what environment your are. ddsl makes the latter easy by providing one cli to use in CI and development environments.

• ruby
• docker
• docker-compose

You can install ddsl with either of this mechansims

Like any ruby gem

gem install ddsl

When running on modern CI providers like Circle CI or GitLab you can install it using the docker image bilby91/ddsl:latest. You can find more information on how to use it by looking at ddsl's Circle CI implementation or GitLab implementation

ddsl it's a command line tool that works with a companion .ddsl.yml file. In the .ddsl.yml file you can declare the diferent builds and runs that your application will need. A very simple example would look like this:

version: 1

builds:
  - name: feature-branch
    type: docker
    context: .
    file: docker/Dockerfile
    tags:
      - bilby91/ddsl:$CI_SHA1
    push: true
    cache_from:
      - bilby91/ddsl:latest

runs:
  - name: test
    type: docker
    image: bilby91/ddsl:$CI_SHA1
    cmd: bundle exec rspec spec

  - name: lint
    type: docker
    image: bilby91/ddsl:$CI_SHA1
    cmd: rubocop .

In order to run our feature-branch build we invoke

ddsl build feature-branch

Now that we have our image built we can run things on it

ddsl run test lint

If you want to inject environmental variables in your build or run definition it's really easy with ddsl. You just need to interpolate the environmental variable name in your .ddsl.yml file like you would do in a bash script in order to get them injected.

Lets take a look at a section of the previous example:

builds:
  - name: feature-branch
    type: docker
    context: .
    file: docker/Dockerfile
    tags:
      - bilby91/ddsl:$CI_SHA1
    push: true
    cache_from:
      - bilby91/ddsl:latest

In this case, our feature-branch build depends on the CI_SHA1 enviromental variable. When invoking CI_SHA1=XXXX ddsl build feature-branch, ddsl will replace CI_SHA1 with the appropiate value (in this case, XXXX) and continue it's normal work.

Templates let you DRY your .ddsl.yml configurations. If you have multiple builds in your project, templates will be very useful for encapsulating common options that all or some of your builds need. Templates can be used in either builds or runs.

Lets take a look at a possible scenario where using templates would make sense.

version: 1

templates:
  - name: base-build
    context: .
    file: docker/Dockerfile
    push: true
    tags:
      - bilby91/ddsl:$CI_SHA1
    cache_from:
      - bilby91/ddsl:latest

builds:
  - name: feature-branch
    type: docker
    templates:
      - base-build

  - name: master
    type: docker
    templates:
      - base-build
    tags:
      - bilby91/ddsl:latest

In the example above we have introduced a new build called master. We have encapsulated all the common options between master and feature-branch in a template called base-build. When ddsl runs either feature-branch or master builds it will merge the options from the template into each build's options.

Some important things to note in regards to templates implementation:

If the templateable object (either a build or a run) have the same key defined, ddsl will behave like this:

1. If the key's value is either a string or a number, the templetable object value will be favored. This allows overriding certain keys when inheriting from a template.
2. If the key's value is an array, the template items of the array will be added to the templatable object array.
3. If the key's value is a map, the template items of the map will be merged in the templatable object map.
   1. If we have a collision here, ddsl will behave like described in point 1.

For the moment, looking at how ddsl uses itself is the best documentation. You can find it here .ddsl.yml.

You can also look at how ddsl integrates with different CI providers

• Circle CI
• GitLab
• Travis

The .ddsl.yml schema documentation can found here

Provider	Status
GitLab CI
Circle CI
Travis CI

• Martín Fernández fmartin91@gmail.com
• Iván Etchart ivan.etchart@me.com