Development guide#

This page provides procedures and guidelines for developing and contributing to Gafaelfawr.

Scope of contributions#

Gafaelfawr is an open source package, meaning that you can contribute to Gafaelfawr itself, or fork Gafaelfawr for your own purposes.

Since Gafaelfawr is intended for internal use by Rubin Observatory, community contributions can only be accepted if they align with Rubin Observatory’s aims. For that reason, it’s a good idea to propose changes with a new GitHub issue before investing time in making a pull request.

Gafaelfawr is developed by the LSST SQuaRE team.

Setting up a local development environment#

To develop Gafaelfawr, create a virtual environment with your method of choice (like virtualenvwrapper) and then clone or fork, and install:

git clone
cd gafaelfawr
make init

This init step does three things:

  1. Installs Gafaelfawr in an editable mode with its “dev” extra that includes test and documentation dependencies.

  2. Installs pre-commit, tox, and tox-docker.

  3. Installs the pre-commit hooks.

On macOS hosts, you may also need to run the following in the terminal window where you run make init and where you intend to run tox commands:

export LDFLAGS="-L/usr/local/opt/openssl/lib"

Otherwise, OpenSSL isn’t on the default linker path and some Python extensions may not build.

Pre-commit hooks#

The pre-commit hooks, which are automatically installed by running the make init command on set up, ensure that files are valid and properly formatted. Some pre-commit hooks automatically reformat code:


Lint Python code and attempt to automatically fix some problems.


Automatically formats Python code.


Automatically formats Python code in reStructuredText documentation and docstrings.

When these hooks fail, your Git commit will be aborted. To proceed, stage the new modifications and proceed with your Git commit.

Building the UI#

Before running tests or starting a local development server, you must build the UI. The Gafaelfawr UI is written in JavaScript and contained in the ui subdirectory. To build it, run (from the top level):

make ui

You will need to have Node.js and npm installed. The easiest way to do this is generally to use nvm. Gafaelfawr provides an .nvmrc file that sets the version of Node.js to what is currently used to build the UI in GitHub Actions for the official Docker image.

Running tests#

To test all components of Gafaelfawr other than the Kubernetes operator (see below), run tox, which tests the library the same way that the CI workflow does:

tox run

This uses tox-docker to start PostgreSQL and Redis Docker containers for the tess to use, so Docker must be installed and the user running tox must have permission to create Docker containers.

To run the Selenium tests, you will need to have chromedriver installed. On Debian and Ubuntu systems, you can install this with apt install chromium-driver.

To run the tests with coverage analysis and generate a report, run:

tox run -e py-coverage,coverage-report

To see a listing of test environments, run:

tox list

To run a specific test or list of tests, you can add test file names (and any other pytest options) after -- when executing the py or py-full tox environment. For example:

tox run -e py -- tests/handlers/

Testing the Kubernetes operator#

To test the Kubernetes operator, you must have a Kubernetes cluster available that is not already running Gafaelfawr. This is only tested with Minikube, which is the approach used by CI.


The default Kubernetes credentials in your local Kubernetes configuration will be used to run the tests, whatever cluster that points to. In theory, you can use a regular Kubernetes cluster and only test namespaces starting with test- will be affected.

In practice, this is not tested, and it is possible the tests will damage or destroy other applications or data running on the same Kubernetes cluster.

If you want to run these tests manually rather than via CI, using Minikube for tests and carefully verifying that the default Kubernetes credentials are for the Minikube environment is strongly encouraged.

To set up Minikube:

  1. Install Minikube for your platform.

  2. Start a cluster using the Docker driver with the minimum recommended resources:

    minikube start --driver=docker --cpus=4 --memory=8g --disk-size=100g  --kubernetes-version=1.21.5

    The --kubernetes-version option can be used to specify the Kubernetes version to use.

  3. Enable the NGINX Ingress Controller using the Minikube ingress addon:


    minikube addons enable ingress

To run all of the tests including Kubernetes tests, first check that your default Kubernetes environment is the one in which you want to run tests:

kubectl config current-context

Then, run:

tox run -e py-full

Add the coverage-report environment to also get a test coverage report.

Starting a development server#

There are two methods to run Gafaelfawr interactively on your local machine for development and testing the UI: outside Docker or inside Docker. In both cases, you will need Docker to be installed on your local machine.

For either approach, you will first need to create a GitHub OAuth app for Gafaelfawr to use. On GitHub, go to your personal settings page, select developer settings, and then select OAuth Apps. Create a new OAuth App with the following settings:

  • Homepage: http://localhost:8080/

  • Authorization callback URL: http://localhost:8080/login

The rest can be set to whatever you want. Replace <github-client-id> in examples/docker/gafaelfawr.yaml and examples/gafaelfawr-dev.yaml with the resulting client ID. Put the resulting secret in examples/secrets/github-client-secret.

Now, use one of the two methods below for running Gafaelfawr.

Outside Docker#


tox run -e run

This will use docker-compose to start Redis and PostgreSQL servers, and then will start Gafaelfawr in the foreground outside of Docker. You can now go to http://localhost:8080/auth/tokens and will be redirected to GitHub for authentication.

To stop the running server, use Ctrl-C. You will then need to manually shut down the Redis and PostgreSQL containers, since tox doesn’t support shutdown commands.

docker-compose down

The advantage of this method is that the running code and UI will be taken from your current working directory, so you can update it on the fly and immediately see the effects.

Inside Docker#

Build a Docker image and start the development instance of Gafaelfawr with:

docker-compose -f examples/docker/docker-compose.yaml --project-directory . build
docker-compose -f examples/docker/docker-compose.yaml --project-directory . up

You can then go to http://localhost:8080/auth/tokens and will be redirected to GitHub for authentication.

To stop the running server, use Ctrl -C. To fully clean up the services, then run:

docker-compose -f examples/docker/docker-compose.yaml --project-directory . down

This way of running Gafaelfawr doesn’t require you to have its dependencies installed locally and more closely simulates a production deployment. However, you will need to stop Gafaelfawr, rebuild the Docker container, and then start it again after each change to see your changes reflected.

Building documentation#

Documentation is built with Sphinx:

tox run -e docs

The build documentation is located in the docs/_build/html directory.

To check the documentation for broken links, run:

tox run -e docs-linkcheck

Updating the change log#

Gafaelfawr uses scriv to maintain its change log.

When preparing a pull request, run scriv create. This will create a change log fragment in changelog.d. Edit that fragment, removing the sections that do not apply and adding entries fo this pull request. You can pass the --edit flag to scriv create to open the created fragment automatically in an editor.

Change log entries use the following sections:

  • Backward-incompatible changes

  • New features

  • Bug fixes

  • Other changes (for minor, patch-level changes that are not bug fixes, such as logging formatting changes or updates to the documentation)

Versioning assumes that Gafaelfawr is installed via Phalanx, so changes to its internal configuration file do not count as backward-incompatible chnages unless they require changes to Helm values.yaml files.

Do not include a change log entry solely for updating pinned dependencies, without any visible change to Gafaelfawr’s behavior. Every release is implicitly assumed to update all pinned dependencies.

These entries will eventually be cut and pasted into the release description for the next release, so the Markdown for the change descriptions must be compatible with GitHub’s Markdown conventions for the release description. Specifically:

  • Each bullet point should be entirely on one line, even if it contains multiple sentences. This is an exception to the normal documentation convention of a newline after each sentence. Unfortunately, GitHub interprets those newlines as hard line breaks, so they would result in an ugly release description.

  • Avoid using too much complex markup, such as nested bullet lists, since the formatting in the GitHub release description may not be what you expect and manually editing it is tedious.

Style guide#


  • Gafaelfawr follows the SQR-072 Python style guide.

  • The code formatting follows PEP 8, though in practice lean on Black and isort to format the code for you.

  • Use PEP 484 type annotations. The tox run -e typing test environment, which runs mypy, ensures that the project’s types are consistent.

  • Gafaelfawr uses the Ruff linter with most checks enabled. Try to avoid noqa markers except for issues that need to be fixed in the future. Tests that generate false positives should normally be disabled, but if the lint error can be avoided with minor rewriting that doesn’t make the code harder to read, prefer the rewriting.

  • Write tests for Pytest.