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Architecture

Scaffold offers a pre-configured project template that is reliable, tested and ready-to-use. Its main goal is to streamline onboarding, making it as quick and efficient as possible.

Zen of DrevOps Scaffold​

Similar to Zen of Python, DrevOps Scaffold has its own set of principles.

  • Simple is better than complex.
  • Rely as much on upstream as possible.
  • Favor standard practices over custom implementations.
  • Errors should never pass silently.
  • Explicit logging helps.
  • Readability counts.
  • If the implementation is hard to explain, it's a bad idea.

Repository structure​

The repository file structure follows the structure defined in drupal-composer/drupal-project with addition of several configuration files and directories.

note

The directory structure is exactly what you are going to get after installation - there are no files being copied or moved from magic places.

├── .circleci                # CircleCI configuration files.
├── .data                    # Database dump files directory. Excluded.
├── .docker                  # Docker configuration files.
│   ├── config               #   Additional configuration for every Docker service.
│   └── scripts              #   Scripts to run in the Docker services during image build
├── .github                  # GitHub configuration files.
├── .logs                    # Test logs and screenshots. Excluded.
├── config                   # Drupal configuration.
│   ├── ci                   #   Config split configuration for CI environment.
│   ├── default              #   Default configuration.
│   ├── dev                  #   Config split configuration for DEV environment.
│   ├── local                #   Config split configuration for local environment.
│   └── test                 #   Config split configuration for test environment.
├── docs                     # Your project documentation.
├── drush                    # Drush configuration files.
├── hooks                    # Acquia hooks. Removed if not using Acquia hosting.
│   ├── common               #   Hook implementations that run on all environments.
│   ├── library              #   Library of hook implementations.
│   └── prod                 #   Hook implementations that run in prod environment.
├── patches                  # Patches for packages.
├── scripts                  # Composer, DrevOps Scaffold and custom project scripts.
│   ├── composer             #   Composer scripts.
│   ├── custom               #   Custom project scripts.
│   └── drevops              #   DrevOps Scaffold workflow scripts.
├── tests                    # Integration and configuration tests.
│   ├── behat                #   Behat BDD tests.
│   └── phpunit              #   Configuration unit tests
├── web                      # Drupal web root directory.
│   ├── modules/custom/ys_core    #  Custom module scaffold.
│   │   ├── tests/src        #         Tests scaffold.
│   │   │   ├── Functional   #           Functional test scaffold and example.
│   │   │   ├── Kernel       #           Kernel test scaffold and example.
│   │   │   ├── Traits       #           Helper traits to use in tests.
│   │   │   └── Unit         #           Unit test scaffold and example.
│   │   └── ys_core.deploy   #         Drush deploy example.
│   └── modules/custom/ys_search  #  Custom search module scaffold.
├── .ahoy.yml                # Ahoy configuration file.
├── .ahoy.local.example.yml  # Ahoy local configuration file.
├── .dockerignore            # Docker ignore configuration file.
├── .editorconfig            # Helps maintain consistent coding styles.
├── .env                     # Environment variables to control project workflow using variables.
├── .env.local.default       # Environment variables local overrides.
├── .gitignore               # Intentionally untracked files to ignore in Git.
├── .gitignore.artifact    # Intentionally untracked files to ignore in artifact deployment.
├── .lagoon.yml              # Lagoon configuration file. Removed if not using Lagoon hosting.
├── .twig-cs-fixer.php       # Twig CS Fixer configuration file.
├── behat.yml                # Behat configuration file.
├── composer.json            # Composer configuration file.
├── docker-compose.yml       # Docker Compose configuration file.
├── docker-compose.override.default.yml # Docker Compose local configuration file.
├── phpcs.xml                # PHP CodeSniffer configuration file.
├── phpmd.xml                # PHP Mess Detector configuration file.
├── phpstan.neon             # PHPStan configuration file.
├── phpunit.xml              # PHPUnit configuration file.
├── README.md                # Project main readme file.
└── renovate.json            # Renovate configuration file.

Scripts​

Scaffold provides a set of POSIX-compliant scripts designed to orchestrate workflows.

During installation, the scripts are added to your project repository into scripts/drevops directory.

note

Using scripts instead of compiled binaries allows for in-place per-project overrides without needing to learn an additional programming language, compile sources, or rely on upstream dependencies.

We are looking into providing pre- and post- hooks for scripts so that you can extend the functionality without modifying the original source code.

We are also looking into a more streamlined way of updating scripts.

Centralised workflows​

A workflow is a sequence of steps or tasks to accomplish a specific goal.

Scaffold comes with as set of pre-defined workflows to standardise the development process.

For example, the scripts/drevops/download-db.sh script is used to download a database from any supported hosting provider or a custom location.

Another example is a scripts/drevops/provision.sh script that is used to provision a website in a consistent way, allowing to alter the flow using environment variables and enhance it via custom scripts.

The scripts aim to centralize workflows instead of adjusting them for every environment (local, CI, dev, prod, etc.), reducing multiple points of failure. This means that a developer updating a workflow for local environment, for example, will not accidentally forget to update it for the CI environment, and so on.

In the diagram below, the download-db.sh and provision.sh scripts are consistently called from the configuration files within an environment.

See Workflows section for more details.

Router scripts​

The script from the example above is a router script that invokes other, more specific scripts (by sourcing them) based on the project configuration. This design keeps the entry point consistent while allowing implementation updates as needed without modifying the entry point in multiple places.

note

The router script always starts with a verb to indicate the action it performs. Specific scripts always start with a name of the router script.

In the diagram below, for example, the download-db.sh script, being a router script, invokes another script specific to the database download source (controlled with an environment variable).

Changing the database download source from lagoon to s3 would not require changes to any local, CI, or hosting scripts.

In addition, a developer would not need to learn how to use s3 to download a database or even know how that download process is setup.

If a new database download method is introduced, the router script download-db.sh can be easily extended to accommodate it, without altering configuration files for services.

Environment variables​

The workflow within scripts is controlled via environment variables.

To alter the workflow for a specific environment, the variables would need to be set within that environment via the .env configuration file or other means supported by the environment (e.g. CircleCI and Acquia support injecting variables via UI).

See Variables section for more details.