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Contribution Workflow

The outline for this document in GitHub is available at top-right corner button (with 3-dots and 3 lines).

Typically, you start your first contribution by reviewing open tickets at GitHub issues.

If you create pull-request, you don't have to create an issue first, but if you want, you can do it. Creating an issue will allow you to collect feedback or share plans with other people.

For example, you want to have the following sample ticket assigned to you: #7782: Add extra CC: to the emails sent by Airflow.

In general, your contribution includes the following stages:

Contribution Workflow

  1. Make your own fork of the Apache Airflow main repository.
  2. Create a local virtualenv, initialize the Breeze environment, and install pre-commit framework. If you want to add more changes in the future, set up your fork and enable GitHub Actions.
  3. Join devlist and set up a Slack account.
  4. Make the change and create a Pull Request (PR) from your fork.
  5. Ping @ #contributors slack, comment @people. Be annoying. Be considerate.

Step 1: Fork the Apache Airflow Repo

From the apache/airflow repo, create a fork:

Creating a fork

Step 2: Configure Your Environment

You can use several development environments for Airflow. If you prefer to have development environments on your local machine, you might choose Local Virtualenv, or dockerized Breeze environment, however we also have support for popular remote development environments: GitHub Codespaces and GitPodify. You can see the differences between the various environments in Development environments.

The local environment instructions can be found in full in the Local virtualenv file.

The Breeze Docker Compose environment is to maintain a consistent and common development environment so that you can replicate CI failures locally and work on solving them locally rather by pushing to CI.

The Breeze instructions can be found in full in the Breeze documentation file.

You can configure the Docker-based Breeze development environment as follows:

1. Install the latest versions of the Docker Community Edition and Docker Compose and add them to the PATH.

  1. Install jq on your machine. The exact command depends on the operating system (or Linux distribution) you use.

For example, on Ubuntu:

sudo apt install jq

or on macOS with Homebrew

brew install jq
  1. Enter Breeze, and run the following in the Airflow source code directory:
breeze

Breeze starts with downloading the Airflow CI image from the Docker Hub and installing all required dependencies.

This will enter the Docker environment and mount your local sources to make them immediately visible in the environment.

  1. Create a local virtualenv, for example:
python3 -m venv venv && source venv/bin/activate
  1. Initialize the created environment:
./scripts/tools/initialize_virtualenv.py
  1. Open your IDE (for example, PyCharm) and select the virtual environment you created as the project's default virtual environment in your IDE.

Step 3: Connect with People

For effective collaboration, make sure to join the following Airflow groups:

Step 4: Prepare PR

  1. Update the local sources to address the issue.

    For example, to address this example issue, do the following:

    • Read about email configuration in Airflow.

    • Find the class you should modify. For the example GitHub issue, this is email.py.

    • Find the test class where you should add tests. For the example ticket, this is test_email.py.

    • Make sure your fork's main is synced with Apache Airflow's main before you create a branch. See How to sync your fork for details.

    • Create a local branch for your development. Make sure to use latest apache/main as base for the branch. See How to Rebase PR for some details on setting up the apache remote. Note, some people develop their changes directly in their own main branches - this is OK and you can make PR from your main to apache/main but we recommend to always create a local branch for your development. This allows you to easily compare changes, have several changes that you work on at the same time and many more. If you have apache set as remote then you can make sure that you have latest changes in your main by git pull apache main when you are in the local main branch. If you have conflicts and want to override your locally changed main you can override your local changes with git fetch apache; git reset --hard apache/main.

    • Modify the class and add necessary code and unit tests.

    • Run and fix all the static checks. If you have pre-commits installed, this step is automatically run while you are committing your code. If not, you can do it manually via git add and then pre-commit run.

    • Run the appropriate tests as described in Testing documentation.

    • Consider adding a newsfragment to your PR so you can add an entry in the release notes. The following newsfragment types are supported:

      • significant
      • feature
      • improvement
      • bugfix
      • doc
      • misc

      To add a newsfragment, create an rst file named {pr_number}.{type}.rst (e.g. 1234.bugfix.rst) and place in either newsfragments for core newsfragments, or chart/newsfragments for helm chart newsfragments.

      In general newsfragments must be one line. For newsfragment type significant, you may include summary and body separated by a blank line, similar to git commit messages.

  2. Rebase your fork, squash commits, and resolve all conflicts. See How to rebase PR if you need help with rebasing your change. Remember to rebase often if your PR takes a lot of time to review/fix. This will make rebase process much easier and less painful and the more often you do it, the more comfortable you will feel doing it.

  3. Re-run static code checks again.

  4. Make sure your commit has a good title and description of the context of your change, enough for maintainers reviewing it to understand why you are proposing a change. Make sure to follow other PR guidelines described in Pull Request guidelines. Create Pull Request! Make yourself ready for the discussion!

  5. The static checks and tests in your PR serve as a first-line-of-check, whether the PR passes the quality bar for Airflow. It basically means that until you get your PR green, it is not likely to get reviewed by maintainers unless you specifically ask for it and explain that you would like to get first pass of reviews and explain why achieving green status for it is not easy/feasible/desired. Similarly if your PR contains [WIP] in the title or it is marked as Draft it is not likely to get reviewed by maintainers unless you specifically ask for it and explain why and what specifically you want to get reviewed before it reaches Ready for review status. This might happen if you want to get initial feedback on the direction of your PR or if you want to get feedback on the design of your PR.

  6. Avoid @-mentioning individual maintainers in your PR, unless you have good reason to believe that they are available, have time and/or interest in your PR. Generally speaking there are no "exclusive" reviewers for different parts of the code. Reviewers review PRs and respond when they have some free time to spare and when they feel they can provide some valuable feedback. If you want to get attention of maintainers, you can just follow-up on your PR and ask for review in general, however be considerate and do not expect "immediate" reviews. People review when they have time, most of the maintainers do such reviews in their free time, which is taken away from their families and other interests, so allow sufficient time before you follow-up - but if you see no reaction in several days, do follow-up, as with the number of PRs we have daily, some of them might simply fall through the cracks, and following up shows your interest in completing the PR as well as puts it at the top of "Recently commented" PRs. However, be considerate and mindful of the time zones, holidays, busy periods, and expect that some discussions and conversation might take time and get stalled occasionally. Generally speaking it's the author's responsibility to follow-up on the PR when they want to get it reviewed and merged.

Step 5: Pass PR Review

PR Review

Note that maintainers will use Squash and Merge instead of Rebase and Merge when merging PRs and your commit will be squashed to single commit.

When a reviewer starts a conversation it is expected that you respond to questions, suggestions, doubts, and generally it's great if all such conversations seem to converge to a common understanding. You do not necessarily have to apply all the suggestions (often they are just opinions and suggestions even if they are coming from seasoned maintainers) - it's perfectly ok that you respond to it with your own opinions and understanding of the problem and your approach and if you have good arguments, presenting them is a good idea.

The reviewers might leave several types of responses:

  • General PR comment - which usually means that there is a question/opinion/suggestion on how the PR can be improved, or it's an ask to explain how you understand the PR. You can usually quote some parts of such general comment and respond to it in your comments. Often comments that are raising questions in general might lead to different discussions, even a request to move the discussion to the devlist or even lead to completely new PRs created as a spin-off of the discussion.

  • Comment/Conversation around specific lines of code - such conversation usually flags a potential improvement, or a potential problem with the code. It's a good idea to respond to such comments and explain your approach and understanding of the problem. The whole idea of a conversation is try to reach a consensus on a good way to address the problem. As an author you can resolve the conversation if you think the problem raised in the comment is resolved or ask the reviewer to re-review, confirm If you do not understand the comment, you can ask for clarifications. Generally assume good intention of the person who is reviewing your code and resolve conversations also having good intentions. Understand that it's not a person that is criticised or argued with, but rather the code and the approach. The important thing is to take care about quality of the the code and the project and want to make sure that the code is good.

    It's ok to mark the conversation resolved by anyone who can do it - it could be the author, who thinks the arguments are changes implemented make the conversation resolved, or the maintainer/person who started the conversation or it can be even marked as resolved by the maintainer who attempts to merge the PR and thinks that all conversations are resolved. However if you want to make sure attention and decision on merging the PR is given by maintainer, make sure you monitor, follow-up and close the conversations when you think they are resolved (ideally explaining why you think the conversation is resolved).

  • Request changes - this is where maintainer is pretty sure that you should make a change to your PR because it contains serious flaw, design misconception, or a bug or it is just not in-line with the common approach Airflow community took on the issue. Usually you should respond to such request and either fix the problem or convince the maintainer that they were wrong (it happens more often than you think). Sometimes even if you do not agree with the request, it's a good idea to make the change anyway, because it might be a good idea to follow the common approach in the project. Sometimes it might even happen that two maintainers will have completely different opinions on the same issue and you will have to lead the discussion to try to achieve consensus. If you cannot achieve consensus and you think it's an important issue, you can ask for a vote on the issue by raising a devlist discussion - where you explain your case and follow up the discussion with a vote when you cannot achieve consensus there. The Request changes status can be withdrawn by the maintainer, but if they don't - such PR cannot be merged - maintainers have the right to veto any code modification according to the Apache Software Foundation rules.

  • Approval - this is given by a maintainer after the code has been reviewed and the maintainer agrees that it is a good idea to merge it. There might still be some unresolved conversations, requests and questions on such PR and you are expected to resolve them before the PR is merged. But the Approval status is a sign of trust from the maintainer who gave the approval that they think the PR is good enough as long as their comments will be resolved and they put the trust in the hands of the author and - possibly - other maintainers who will merge the request that they can do that without follow-up re-review and verification.

You need to have Approval of at least one maintainer (if you are maintainer yourself, it has to be another maintainer). Ideally you should have 2 or more maintainers reviewing the code that touches the core of Airflow - we do not have enforcement about 2+ reviewers required for Core of Airflow, but maintainers will generally ask in the PR if they think second review is needed.

Your PR can be merged by a maintainer who will see that the PR is approved, all conversations are resolved and the code looks good. The criteria for PR being merge-able are:

  • green status for static checks and tests
  • conversations resolved
  • approval from 1 (or more for core changes) maintainers
  • no unresolved Request changes

Once you reach the status, you do not need to do anything to get the PR merged. One of the maintainers will merge such PRs. However if you see that for a few days such a PR is not merged, do not hesitate to comment on your PR and mention that you think it is ready to be merged. Also, it's a good practice to rebase your PR to latest main, because there could be other changes merged in the meantime that might cause conflicts or fail tests or static checks, so by rebasing a PR that has been build few days ago you make sure that it still passes the tests and static checks today.