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How to Contribute

When submitting a pull request (PR), please use the following guidelines:

  • Make sure your code respects existing formatting conventions. In general, follow the same coding style as the code that you are modifying.
  • For Intellij you can import our code style settings xml: druid_intellij_formatting.xml.
  • For Eclipse you can import our code style settings xml: eclipse_formatting.xml.
  • Do add/update documentation appropriately for the change you are making.
  • If you are introducing a new feature you may want to first write about your idea for feedback to dev@druid.apache.org. Non-trivial features should include unit tests covering the new functionality.
  • Bugfixes should include a unit test or integration test reproducing the issue.
  • Do not use author tags/information in the code.
  • Always include license header on each java file your create. See this example
  • Try to keep pull requests short and submit separate ones for unrelated features, but feel free to combine simple bugfixes/tests into one pull request.
  • Keep the number of commits small and combine commits for related changes. Each commit should compile on its own and ideally pass tests.
  • Keep formatting changes in separate commits to make code reviews easier and distinguish them from actual code changes.

GitHub Workflow

  1. Fork the apache/incubator-druid repository into your GitHub account

    https://github.com/apache/incubator-druid/fork

  2. Clone your fork of the GitHub repository

    git clone git@github.com:<username>/druid.git

    replace <username> with your GitHub username.

  3. Add a remote to keep up with upstream changes

    git remote add upstream https://github.com/apache/incubator-druid.git
    

    If you already have a copy, fetch upstream changes

    git fetch upstream master
    
  4. Create a feature branch to work in

    git checkout -b feature-xxx remotes/upstream/master
    
  5. Before submitting a pull request periodically rebase your changes (but don't do it when a pull request is already submitted)

    git pull --rebase upstream master
    
  6. Before submitting a pull request, combine ("squash") related commits into a single one

    git rebase -i upstream/master
    

    This will open your editor and allow you to re-order commits and merge them:

    • Re-order the lines to change commit order (to the extent possible without creating conflicts)
    • Prefix commits using s (squash) or f (fixup) to merge extraneous commits.
  7. Submit a pull-request

    git push origin feature-xxx
    

    Go to your Druid fork main page

    https://github.com/<username>/druid
    

    If you recently pushed your changes GitHub will automatically pop up a Compare & pull request button for any branches you recently pushed to. If you click that button it will automatically offer you to submit your pull-request to the apache/incubator-druid repository.

    • Give your pull-request a meaningful title.
    • In the description, explain your changes and the problem they are solving.
  8. Addressing code review comments

    Address code review comments by committing changes and pushing them to your feature branch.

    git push origin feature-xxx
    

If your pull request shows conflicts with master

If your pull request shows conflicts with master, merge master into your feature branch:

git merge upstream/master

and resolve the conflicts. After resolving conflicts, push your branch again:

git push origin feature-xxx

Avoid rebasing and force pushes after submitting a pull request, since these make it difficult for reviewers to see what you've changed in response to their reviews. The Druid committer that merges your change will rebase and squash it into a single commit before committing it to master.

FAQ

Help! I merged changes from upstream and cannot figure out how to resolve conflicts when rebasing!

Never fear! If you occasionally merged upstream/master, here is another way to squash your changes into a single commit:

  1. First, rename your existing branch to something else, e.g. feature-xxx-unclean
git branch -m feature-xxx-unclean
  1. Checkout a new branch with the original name feature-xxx from upstream. This branch will supercede our old one.
git checkout -b feature-xxx upstream/master
  1. Then merge your changes in your original feature branch feature-xxx-unclean and create a single commit.
git merge --squash feature-xxx-unclean
git commit
  1. You can now submit this new branch and create or replace your existing pull request.
git push origin [--force] feature-xxx:feature-xxx