This document is a guide intended for folks interested in contributing to dbt. It is not intended as a guide for end users of dbt (though if it is helpful, that's great!) and it assumes a certain level of familiarity with Python concepts such as virtualenvs, pip, python modules, filesystems, and so on. It also assumes you are using macOS or Linux and are comfortable with the command line. If you get stuck while reading this guide, drop us a line in the #development channel on slack.
You will need git in order to download and modify the dbt source code. On macOS, the best way to download git is to just install Xcode.
If you are not a member of the fishtown-analytics GitHub organization, you can contribute to dbt by forking the dbt repository. For a detailed overview on forking, check out the GitHub docs on forking. In short, you will need to:
- fork the dbt repository
- clone your fork
- check out a new branch for your proposed changes
- push changes to your fork
- open a pull request against
fishtown-analytics/dbtfrom your forked repository
If you are a member of the fishtown-analytics GitHub organization, you will have push access to the dbt repo. Rather than
forking dbt to make your changes, just clone the repository and push directly to a branch.
To begin developing code in dbt, you should set up the following:
We strongly recommend using virtual environments when developing code in dbt. We recommend creating this virtualenv in the root of the dbt repository. To create a new virtualenv, run:
python3 -m venv env
source env/bin/activate
This will create and activate a new Python virtual environment.
Docker and docker-compose are both used in testing. For macOS, the easiest thing to do is to download docker for mac. You'll need to make an account. On Linux, you can use one of the packages here. We recommend installing from docker.com instead of from your package manager. On Linux you also have to install docker-compose separately, follow these instructions.
For testing, and later in the examples in this document, you may want to have psql available so you can poke around in the database and see what happened. We recommend that you use homebrew for that on macOS, and your package manager on Linux. You can install any version of the postgres client that you'd like. On macOS, with homebrew setup, you can run:
brew install postgresql
First make sure that you set up your virtualenv as described in section Setting up an environment. Next, install dbt (and it's dependencies) with:
pip install -r requirements.txt
When dbt is installed from source in this way, any changes you make to the dbt source code will be reflected immediately in your next dbt run.
With your virtualenv activated, the dbt script should point back to the source code you've cloned on your machine. You can verify this by running which dbt. This command should show you a path to an executable in your virtualenv.
Configure your profile as necessary to connect to your target databases. It may be a good idea to add a new profile pointing to a local postgres instance, or a specific test sandbox within your data warehouse if appropriate.
Getting the dbt integration tests set up in your local environment will be very helpful as you start to make changes to your local version of dbt. The section that follows outlines some helpful tips for setting up the test environment.
A short list of tools used in dbt testing that will be helpful to your understanding:
- virtualenv to manage dependencies
- tox to manage virtualenvs across python versions
- pytest to discover/run tests
- make - but don't worry too much, nobody really understands how make works and our Makefile is super simple
- flake8 for code linting
- CircleCI and Azure Pipelines
A deep understanding of these tools in not required to effectively contribute to dbt, but we recommend checking out the attached documentation if you're interested in learning more about them.
dbt's unit and integration tests run in Docker. Because dbt works with a number of different databases, you will need to supply credentials for one or more of these databases in your test environment. Most organizations don't have access to each of a BigQuery, Redshift, Snowflake, and Postgres database, so it's likely that you will be unable to run every integration test locally. Fortunately, Fishtown Analytics provides a CI environment with access to sandboxed Redshift, Snowflake, BigQuery, and Postgres databases. See the section on Submitting a Pull Request below for more information on this CI setup.
dbt uses test credentials specified in a test.env file in the root of the repository. This test.env file is git-ignored, but please be extra careful to never check in credentials or other sensitive information when developing against dbt. To create your test.env file, copy the provided sample file, then supply your relevant credentials:
cp test.env.sample test.env
atom test.env # supply your credentials
We recommend starting with dbt's Postgres tests. These tests cover most of the functionality in dbt, are the fastest to run, and are the easiest to set up. dbt's test suite runs Postgres in a Docker container, so no setup should be required to run these tests. If you additionally want to test Snowflake, Bigquery, or Redshift locally you'll need to get credentials and add them to the test.env file.
dbt's unit tests and Python linter can be run with:
make test-unit
To run the Postgres + Python 3.6 integration tests, you'll have to do one extra step of setting up the test database:
docker-compose up -d database
PGHOST=localhost PGUSER=root PGPASSWORD=password PGDATABASE=postgres bash test/setup_db.sh
To run a quick test for Python3 integration tests on Postgres, you can run:
make test-quick
To run tests for a specific database, invoke tox directly with the required flags:
# Run Postgres py36 tests
docker-compose run test tox -e integration-postgres-py36 -- -x
# Run Snowflake py36 tests
docker-compose run test tox -e integration-snowflake-py36 -- -x
# Run BigQuery py36 tests
docker-compose run test tox -e integration-bigquery-py36 -- -x
# Run Redshift py36 tests
docker-compose run test tox -e integration-redshift-py36 -- -x
See the Makefile contents for more some other examples of ways to run tox.
Fishtown Analytics provides a sandboxed Redshift, Snowflake, and BigQuery database for use in a CI environment.
When pull requests are submitted to the fishtown-analytics/dbt repo, GitHub will trigger automated tests in CircleCI and Azure Pipelines. If the PR submitter is a member of the fishtown-analytics GitHub organization, then the credentials for these databases will be automatically supplied as environment variables in the CI test suite.
If the PR submitter is not a member of the fishtown-analytics organization, then these environment variables will not be automatically supplied in the CI environment. Once a core maintainer has taken a look at the Pull Request, they will kick off the test suite with the required credentials.
Once your tests are passing and your PR has been reviewed, a dbt maintainer will merge your changes into the active development branch! And that's it! Happy developing 🎉