Apache Beam Contribution Guide
The Apache Beam community welcomes contributions from anyone!
If you have questions, please reach out to the Beam community.
There are lots of opportunities to contribute:
- ask or answer questions on firstname.lastname@example.org or stackoverflow
- review proposed design ideas on email@example.com
- improve the documentation
- contribute bug reports
- contribute by testing releases
- contribute by reviewing changes
- write new examples
- improve your favorite language SDK (Java, Python, Go, etc)
- improve specific runners (Apache Apex, Apache Flink, Apache Spark, Google Cloud Dataflow, etc)
- improve or add IO connectors
- add new transform libraries (statistics, ML, image processing, etc)
- work on the core programming model (what is a Beam pipeline and how does it run?)
- improve the developer experience (for example, Windows guides)
- add answers to the contribution FAQ
- organize local meetups of users or contributors to Apache Beam
Most importantly, if you have an idea of how to contribute, then do it!
Below is a tutorial for contributing code to Beam, covering our tools and typical process in detail.
To contribute code, you need
- a GitHub account
- a Linux, macOS, or Microsoft Windows development environment with Java JDK 8 installed
- Docker installed for some tasks including building worker containers and testing website changes locally
- Go 1.10 or later installed for Go SDK development
- Python, virtualenv, and tox installed for Python SDK development
- for large contributions, a signed Individual Contributor License Agreement (ICLA) to the Apache Software Foundation (ASF).
Connect With the Beam community
- Consider subscribing to the dev@ mailing list, especially if you plan to make more than one change or the change will be large. All decisions happen on the public dev list.
- (Optionally) Join the #beam channel of the ASF slack.
- Create an account on Beam issue tracker (JIRA) (anyone can do this).
Share your intent
- Find or create an issue in the Beam issue tracker (JIRA). Tracking your work in an issue will avoid duplicated or conflicting work, and provide a place for notes. Later, your pull request will be linked to the issue as well.
- If you want to get involved but don’t have a project in mind, check our list of open starter tasks, https://s.apache.org/beam-starter-tasks.
- Assign the issue to yourself. To get the permission to do so, email the dev@ mailing list to introduce yourself and to be added as a contributor in the Beam issue tracker including your ASF Jira Username. For example this welcome email.
- If your change is large or it is your first change, it is a good idea to discuss it on the dev@ mailing list.
- For large changes create a design doc (template, examples) and email it to the dev@ mailing list.
- If you need help with git forking, cloning, branching, committing, pull requests, and squashing commits, see Git workflow tips
Familiarize yourself with gradle and the project structure. At the root of the git repository, run:
$ ./gradlew projects
Examine the available tasks in a project. For the default set of tasks, use:
$ ./gradlew tasks
For a given module, use:
$ ./gradlew -p sdks/java/io/cassandra tasks
For an exhaustive list of tasks, use:
$ ./gradlew tasks --all
Make sure you can build and run tests
Run the entire set of tests with:
$ ./gradlew check
You can limit testing to a particular module. Gradle will build just the necessary things to run those tests. For example:
$ ./gradlew -p sdks/go check $ ./gradlew -p sdks/java/io/cassandra check $ ./gradlew -p runners/flink check
- Now you may want to set up your preferred IDE and other aspects of your development environment. See the Developers’ wiki for tips, guides, and FAQs on:
Make your change
Make your code change. Every source file needs to include the Apache license header. Every new dependency needs to have an open source license compatible with Apache.
Add unit tests for your change.
Use descriptive commit messages that make it easy to identify changes and provide a clear history.
When your change is ready to be reviewed and merged, create a pull request.
Format commit messages and the pull request title like
[BEAM-XXX] Fixes bug in ApproximateQuantiles, where you replace BEAM-XXX with the appropriate JIRA issue. This will automatically link the pull request to the issue.
The pull request and any changes pushed to it will trigger pre-commit jobs. If a test fails and appears unrelated to your change, you can cause tests to be re-run by adding a single line comment on your PR
retest this please
Pull request template has a link to a catalog of trigger phrases that start various post-commit tests suites. Use these sparingly because post-commit tests consume shared development resources.
- Pull requests can only be merged by a
To find a committer for your area, either:
- look in the OWNERS file of the directory where you changed files, or
- look for similar code merges, or
- ask on firstname.lastname@example.org
R: @usernamein the pull request to notify a reviewer.
- If you don’t get any response in 3 business days, email the dev@ mailing list to ask for someone to look at your pull request.
Make reviewer’s job easier
Provide context for your changes in the associated JIRA issue and/or PR description.
Avoid huge mega-changes.
Review feedback typically leads to follow-up changes. It is easier to review follow-up changes when they are added as additional “fixup” commits to the existing PR/branch. This allows reviewer(s) to track the incremental progress and focus on new changes, and keeps comment threads attached to the code. Please refrain from squashing new commits into reviewed commits before review is completed. Because squashing reviewed and unreviewed commits often makes it harder to see the the difference between the review iterations, reviewers may ask you to unsquash new changes.
After review is complete and the PR is accepted, fixup commits should be squashed (see Git workflow tips). Beam committers can squash all commits in the PR during merge, however if a PR has a mixture of independent changes that should not be squashed, and fixup commits, then the PR author should help squashing fixup commits to maintain a clean commmit history.
When will my change show up in an Apache Beam release?
Apache Beam makes minor releases every 6 weeks. Apache Beam has a calendar for cutting the next release branch. Your change needs to be checked into master before the release branch is cut to make the next release.
Stale pull requests
The community will close stale pull requests in order to keep the project healthy. A pull request becomes stale after its author fails to respond to actionable comments for 60 days. Author of a closed pull request is welcome to reopen the same pull request again in the future. The associated JIRAs will be unassigned from the author but will stay open.
Accounts and Permissions
Beam issue tracker (JIRA): Anyone can access it and browse issues. Anyone can register an account and login to create issues or add comments. Only contributors can be assigned issues. If you want to be assigned issues, a PMC member can add you to the project contributor group. Email the dev@ mailing list to ask to be added as a contributor in the Beam issue tracker, and include your ASF Jira username.
Pull requests can only be merged by a Beam committer.
All communication is expected to align with the Code of Conduct.
Discussion about contributing code to Beam happens on the dev@ mailing list. Introduce yourself!
Questions can be asked on the #beam channel of the ASF slack. Introduce yourself!
If you are contributing a
PTransform to Beam, we have an extensive
PTransform Style Guide.
If you are contributing a Runner to Beam, refer to the Runner authoring guide
Review design documents.
A great way to contribute is to join an existing effort. For the most intensive efforts, check out the roadmap.
You can also find a more exhaustive list on the Beam developers’ wiki
If you didn’t find the information you were looking for in this guide, please reach out to the Beam community.