Bazel Release Playbook

This is the guide to conducting a Bazel release. This is especially relevant for release managers, but will be of interest to anyone who is curious about the release process.

Setup

Do these steps once per release.

• Set up github ssh key if you haven't already.
  • https://help.github.com/articles/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent/
• Find baseline commit and cherrypicks
  • Check Bazel nightly build at https://buildkite.com/bazel/bazel-with-downstream-projects-bazel. If many downstream jobs are failing then this isnot a good baseline commit. If only a few downstream jobs are failing and the issues are known then this is a good baseline commit. Fixes for the known issues should be cherry-picked, any remaining issues should become release blockers.

Release issue

Each release has a tracking bug (see the list). The last and the next releases should be pinned. The bug includes a “Target RC date”. On that day, create a new release candidate.

The release manager adds a comment to the issue with the following content:

# Status of Bazel X.Y

- Target baseline: [date]
- Expected release date: [date]
- [List of release blockers](https://github.com/bazelbuild/bazel/labels/Release%20blocker)

To report a release-blocking bug, please file a bug using the `Release blocker` label, and cc me.

Task list:

- [ ] Update GitHub issues for incompatible changes
- [ ] Pick release baseline:
- [ ] Create release candidate:
- [ ] Check downstream projects:
- [ ] [Create draft release announcement](https://docs.google.com/document/d/1wDvulLlj4NAlPZamdlEVFORks3YXJonCjyuQMUQEmB0/edit)
- [ ] Send for review the release announcement PR:
- [ ] Push the release, notify package maintainers:
- [ ] Update the documentation
- [ ] Push the blog post
- [ ] Update the [release page](https://github.com/bazelbuild/bazel/releases/)

Keep the task list updated and check boxes as you follow the release process. Example.

Update the status of GitHub issues for incompatible changes

In the below, X.Y is a release you are cutting.

Start new migration windows

1. Search for all open “incompatible-change” issues that have “migration-ready” labels
2. For each such issue:
   1. Add a “migration-X.Y” label.
   2. Add a “breaking-change-X.Y+w” label where w is the length of migration window for that particular issue
   3. Remove “migration-ready” label

Review breaking changes

(skip this section if you're not creating a major release)

1. Search for issues with label “breaking-change-X.Y”.
2. For all such issues that are closed, verify that the flag is flipped and release notes mention the breaking change.
   1. If the flag is not flipped, you probably need to reopen the issue and follow the steps as if the issue was open. Ping the author as well.
   2. If the release notes do not mention the breaking change, manually add the flag to the release notes (under “Prepare the Release Announcement” section).
3. For all such issues that are still open:
   1. remove the label “breaking-change-X.Y”.
   2. add a label “migration-X.Y” and “breaking-change-X.Y+1” (this prolongs the migration window by 1 release).
   3. Reach out to the issue owner.

Prolong ongoing migration windows

1. Search for issues with labels “migration-X.Y-1” that are not “migration-X.Y” and not “breaking-change-X.Y”
2. For all such issues, apply “migration-X.Y” label. Do not remove any previous “migration-X.Y-1” labels.

Create a Candidate

Create candidates with the release.sh script.

• If it's the first candidate for this version, run:

  RELEASE_NUMBER=<CURRENT RELEASE NUMBER x.yy.z>
  BASELINE_COMMIT=01234567890abcdef # From the Setup phase
  git clone https://github.com/bazelbuild/bazel.git ~/bazel-release-$RELEASE_NUMBER
  cd ~/bazel-release-$RELEASE_NUMBER
  scripts/release/release.sh create $RELEASE_NUMBER $BASELINE_COMMIT [CHERRY_PICKS...]
  

  Note that the three-digit version is important: “0.19.0”. not “0.19”.

• For cherry-picks, you need --force_rc=N where N is the number of the release candidate of $RELEASE_NUMBER. For example, the first time you do a cherry-pick (after the initial candidate), N will be 2.

  scripts/release/release.sh create --force_rc=2 $RELEASE_NUMBER $BASELINE_COMMIT [CHERRY_PICKS...]
  

• If you already did some cherry-picks and you want to add more, use “git log” to find the latest commit (this corresponds to the last cherry-pick commit). Use that as the new baseline and list the new cherry-picks to add on top. Or simply re-use the same baseline and cherrypicks from the previous candidate, and add the new cherrypicks.

  scripts/release/release.sh create --force_rc=3 $RELEASE_NUMBER NEW_BASELINE_COMMIT [NEW_CHERRY_PICKS...]
  

Resolve conflicts if there are any, type exit when you are done, then the script will continue. WARNING: release.sh create handles conflicts in a subshell (which is why you need to type exit).

Editing the release notes is not needed (it will be done later).

Push the candidate

1. Run release.sh push. This uploads the candidate and starts the release process on BuildKite.

   scripts/release/release.sh push
   

2. Update GitHub issue with the command that was run and the new candidate name (ie, 0.19.1rc3). Update the issue with the estimated release date, assuming no regression is found.

3. Check BuildKite results at https://buildkite.com/bazel-trusted/bazel-release. You should see the release-$RELEASE_NUMBER branch here and a new build running for your release.

4. Check the postsubmit test run for the release branch to ensure that all tests on all platforms pass with the version you're about to release.

   • Go to https://buildkite.com/bazel/bazel-bazel and find the release-$RELEASE_NUMBER branch in the list. A build should automatically run. Make sure that it passes.

5. When it all looks good, go back to the job in the release pipeline, click “Unblock step” for the deployment step.

   • This will upload the release candidate binaries to GitHub and our apt-get repository. The github link is probably of the form: https://releases.bazel.build/0.25.0/rc1/index.html

   • If you don't have the permission, ask one of the Buildkite org admins to add you to the release-managers group.

6. If that worked, click “Unblock step” for the “Generate Announcement” step. If it's the first release candidate, prepare the release announcement (see next section).

7. Copy & paste the generated text into a new e-mail and send it. If you're creating a new release candidate, reply to the previous e-mail to keep all the information in one thread.

   • The first line is the recipient address.
   • The second line is the subject.
   • The rest is the body of the message.
   • Replace the generated notes with a link to the release announcement draft.

8. Trigger a new pipeline in BuildKite to test the release candidate with all the downstream projects.

   • Go to https://buildkite.com/bazel/bazel-with-downstream-projects-bazel
   • Click “New Build”, then fill in the fields like this:
     • Message: Test Release-0.14.0rc1 (Or any message you like)
     • Commit: HEAD
     • Branch: release-0.14.0

9. Look for failing projects in red.

   • Compare the results with the latest Bazel release:

     • Jobs built with the latest Bazel: https://buildkite.com/bazel?team=bazel
     • Jobs built with release candidate: e.g. https://buildkite.com/bazel/bazel-with-downstream-projects-bazel/builds/287

     If a project is failing with release candidate but not with the latest Bazel release, then there's probably a regression in the candidate. Ask the Bazel sheriff if the problem is already noticed. If not, find out the culprit, file an issue at https://github.com/bazelbuild/bazel/issues and mark it as release blocker.

     If a project is failing with both release candidate and the latest Bazel release, it could be a breakage from the project itself. Go through the build history (eg. TensorFlow_serving) to confirm this, then file an issue to their owners.

   • File bugs (TODO: how to find the owner/project link?)

10. Once issues are fixed, create a new candidate with the relevant cherry-picks.

Release announcement

The release manager is responsible for the draft release announcement.

Once the first candidate is available:

1. Open the doc, create a new section with your release number, add a link to the GitHub issue.
2. Copy & paste the generated text from the “Generate Announcement” step.
3. Reorganize the notes per category (C++, Java, etc.).
4. For each category, add a comment and assign it to the corresponding team contact: “+person for review (see guidelines at the top of the doc)”.
5. Send an email to bazel-dev for additional reviews.
6. Assign a comment to “+aiuto@google.com” for a global review.

After a few days of iteration:

1. Make sure all comments have been resolved, and the text follows the guidelines (see “How to review the notes?” in the document).
2. Send a pull request to bazel-blog.

Release requirements

1. The release announcement must be ready (the pull request has been reviewed).
2. Verify that the conditions outlined in our policy all apply. As of May 2019 those were the following, but double check that they have not changed since then.
   1. at least 1 week passed since you pushed RC1, and
   2. at least 2 business days passed since you pushed the last RC, and
   3. there are no open “Release blocking” Bazel bugs on GitHub.

Push a release

1. Generate a new identifier: https://bazel.googlesource.com/new-password (and paste the code in your shell). This is only necessary the first time you handle a release.

2. Push the final release (do not cancel midway):

   scripts/release/release.sh release
   

3. A CI job is uploading the release artifacts to GitHub. Look for the release workflow on https://buildkite.com/bazel-trusted/bazel-release/. Unblock the steps.

4. Ensure all binaries were uploaded to GitHub properly.

   1. Why? Sometimes binaries are uploaded incorrectly.
   2. How? Go to the GH releases page, click “Edit”, see if there's a red warning sign next to any binary. You need to manually upload those; get them from https://storage.googleapis.com/bazel/$RELEASE_NUMBER/release/index.html.

5. Update the release bug:

   1. State the fact that you pushed the release
   2. Ask the package maintainers to update the package definitions: @vbatts @petemounce @excitoon
   3. Example: [https://github.com/bazelbuild/bazel/issues/3773#issuecomment-352692144]

6. Publish versioned documentation

   1. Fetch the git tag for the release: git fetch --tags

   2. Do a checkout to that tag: git checkout $RELEASE_NUMBER

      1. You should see this message (e.g. for 0.21.0):

      $ git checkout 0.21.0
      Note: checking out '0.21.0'.
      
      You are in 'detached HEAD' state. You can look around, make experimental
      changes and commit them, and you can discard any commits you make in this
      state without impacting any branches by performing another checkout.
      
      If you want to create a new branch to retain commits you create, you may
      do so (now or later) by using -b with the checkout command again. Example:
      
      git checkout -b <new-branch-name>
      
      HEAD is now at defd737761 Release 0.21.0 (2018-12-19)
      

   3. Install gsutil and ensure you have access to the bazel-public GCP project.

   4. Run scripts/docs/generate_versioned_docs.sh. If you get interrupted, it is safe to re-run the script. This script will build the web assets for the documentation, generate a tarball from them, and push the tarball to Google Cloud Storage.

      • The script will fail to run if you're not in a git checkout of a release.
      • If the tarball has already been pushed to GCS, this script will not overwrite the existing tarball.

   5. Update site/_config.yml and scripts/docs/doc_versions.bzl with $RELEASE_NUMBER.

      1. site/_config.yml: set version: to $RELEASE_NUMBER and add $RELEASE_NUMBER to doc_versions:.
      2. scripts/docs/doc_versions.bzl: add the following list item to DOC_VERSIONS
      3. After the changes are submitted, it will take 30 mins-1 hour for them to show up on bazel.build.

7. Merge the blog post pull request.

8. Update the release page to replace the generated notes with a link to the blog post.

9. Close the release-tracking bug. If you need to do a patch release, create a new tracking bug.

Updating the Homebrew recipe

Homebrew is a package manager for OS X. This section assumes that you are on a Mac OS machine with homebrew installed.

To update the bazel recipe on Homebrew, you must send a pull request to https://github.com/bazelbuild/homebrew-tap

Updating the Chocolatey package

As of November 2016, this is done by an external contributor, @petemounce on GitHub. Ping him when there's a new release coming out.

Updating the Scoop pakage

As of February 2019, this is done by an external contributor, @excitoon on GitHub. Ping him when there's a new release coming out.

Updating the Fedora package

This is done by an external contributor, @vbatts on GitHub. Ping him when there's a new release coming out.