Backporting process

Backport Criteria

Committers may nominate PRs that have been merged into main as candidates for backport into stable releases if they affect the stable production usage of community users.

Backport Criteria for Current Minor Release

Criteria for inclusion into the next stable release of the current latest minor version of Cilium, for example in a v1.2.z release prior to the release of version v1.3.0:

  • All bugfixes

  • Debug tool improvements

Backport Criteria for X.Y-1.Z and X.Y-2.Z

Criteria for the inclusion into the next stable release of the prior two minor versions of Cilium, for example in a v1.0.z or v1.1.z release prior to the release of version v1.3.0:

  • Security relevant fixes

  • Major bugfixes relevant to the correct operation of Cilium

  • Debug tool improvements

Backport Criteria for documentation changes

Changes to Cilium’s documentation should generally be subject to backports for all supported branches to which they apply (all supported branches containing the parent features to which the modified sections relate).

The motivation is that users can then simply look at the branch of the documentation related to the version they are deploying, and find the latest correct instructions for their version.

Proposing PRs for backporting

PRs are proposed for backporting by adding a needs-backport/X.Y label to them. Normally this is done by the author when the PR is created or one of the maintainers when the PR is reviewed. When proposing PRs that have already been merged, also add a comment to the PR to ensure that the backporters are notified.

Marking PRs to be backported by the author

For PRs which need to be backported, but are likely to run into conflicts or other difficulties, the author has the option of adding the backport/author label. This will exclude the PR from backporting automation, and the author is expected to perform the backport themselves.

Backporting Guide for the Backporter

Cilium PRs that are marked with the label needs-backport/X.Y need to be backported to the stable branch X.Y. The following steps summarize the process for backporting these PRs:

  • One-time setup

  • Preparing PRs for backport

  • Cherry-picking commits into a backport branch

  • Posting the PR and updating GitHub labels

One-time Setup

  1. Make sure you have a GitHub developer access token with the public_repos workflow, read:user scopes available. You can do this directly from https://github.com/settings/tokens or by opening GitHub and then navigating to: User Profile -> Settings -> Developer Settings -> Personal access token -> Generate new token.

  2. The scripts referred to below need to be run on Linux, they do not work on macOS. It is recommended to create a container using (contrib/backporting/Dockerfile), as it will have all the correct versions of dependencies / libraries.

    $ export GITHUB_TOKEN=<YOUR_GITHUB_TOKEN>

$ docker build -t cilium-backport contrib/backporting/.

$ docker run -e GITHUB_TOKEN -v $(pwd):/cilium -v "$HOME/.ssh":/home/user/.ssh \
      -it cilium-backport /bin/bash

    Note

    If you are running on a mac OS, and see /home/user/.ssh/config: line 3: Bad configuration option: usekeychain error message while running any of the backporting scripts, comment out the line UseKeychain yes.

  3. Once you have a setup ready, you need to configure git to have your name and email address to be used in the commit messages:

    $ git config --global user.name "John Doe"
$ git config --global user.email johndoe@example.com

  4. Add remotes for the Cilium upstream repository and your Cilium repository fork.

    $ git remote add johndoe git@github.com:johndoe/cilium.git
$ git remote add upstream https://github.com/cilium/cilium.git

  5. Skip this step if you have created a setup using the pre-defined Dockerfile. This guide makes use of several tools to automate the backporting process. The basics require bash and git, but to automate interactions with github, further tools are required.

    Dependency

    Required?

    Download Command

    bash

    Yes

    N/A (OS-specific)

    git

    Yes

    N/A (OS-specific)

    jq

    Yes

    N/A (OS-specific)

    python3

    Yes

    Python Downloads

    PyGithub

    Yes

    pip3 install PyGithub

    Github hub CLI (>= 2.8.3)

    Yes

    N/A (OS-specific)

    Verify your machine is correctly configured by running

    $ go run ./tools/dev-doctor --backporting

Preparation

Pull requests that are candidates for backports to the X.Y stable release are tracked through the following links:

Make sure that the Github labels are up-to-date, as this process will deal with all commits from PRs that have the needs-backport/X.Y label set (for a stable release version X.Y).

Creating the Backports Branch

  1. Check whether there are any outstanding backport PRs for the target branch. If there are already backports for that branch, create a thread in the #launchpad channel in Cilium Slack and reach out to the author to coordinate triage, review and merge of the existing PR into the target branch.

  2. Run contrib/backporting/start-backport for the release version that you intend to backport PRs for. This will pull the latest repository commits from the Cilium repository (assumed to be the git remote origin), create a new branch, and runs the contrib/backporting/check-stable script to fetch the full set of PRs to backport.

    $ GITHUB_TOKEN=xxx contrib/backporting/start-backport 1.0

    Note

    This command will leave behind a file in the current directory with a name based upon the release version and the current date in the form vRELEASE-backport-YYYY-MM-DD.txt which contains a prepared backport pull-request description so you don’t need to write one yourself.

  3. Cherry-pick the commits using the main branch git SHAs listed, starting from the oldest (top), working your way down and fixing any merge conflicts as they appear. Note that for PRs that have multiple commits you will want to check that you are cherry-picking oldest commits first. The cherry-pick script accepts multiple arguments, in which case it will attempt to apply each commit in the order specified on the command line until one cherry pick fails or every commit is cherry-picked.

    $ contrib/backporting/cherry-pick <oldest-commit-sha>
...
$ contrib/backporting/cherry-pick <newest-commit-sha>

    Conflicts may be resolved by applying changes or backporting other PRs to completely avoid conflicts. Backporting entire PRs is preferred if the changes in the dependent PRs are small. This stackoverflow.com question describes how to determine the original PR corresponding to a particular commit SHA in the GitHub UI.

    If a conflict is resolved by modifying a commit during backport, describe the changes made in the commit message and collect these to add to the backport PR description when creating the PR below. This helps to direct backport reviewers towards which changes may deviate from the original commits to ensure that the changes are correctly backported. This can be fairly simple, for example inside the commit message of the modified commit:

    commit f0f09158ae7f84fc8d888605aa975ce3421e8d67
Author: Joe Stringer <joe@cilium.io>
Date:   Tue Apr 20 16:48:18 2021 -0700

    contrib: Automate digest PR creation

    [ upstream commit 893d0e7ec5766c03da2f0e7b8c548f7c4d89fcd7 ]

    [ Backporter's notes: Dropped conflicts in .github/ issue template ]

    There's still some interactive bits here just for safety, but one less
    step in the template.

    Signed-off-by: Joe Stringer <joe@cilium.io>

    It is the backporter’s responsibility to check that the backport commits they are preparing are identical to the original commits. This can be achieved by preparing the commits, then running git show <commit> for both the original upstream commit and the prepared backport, and read through the commits side-by-side, line-by-line to check that the changes are the same. If there is any uncertainty about the backport, reach out to the original author directly to coordinate how to prepare the backport for the target branch.

  4. For backporting commits that update cilium-builder and cilium-runtime images, the backporter builds new images as described in Update cilium-builder and cilium-runtime images.

  5. (Optional) If there are any commits or pull requests that are tricky or time-consuming to backport, consider reaching out for help on Cilium Slack. If the commit does not cherry-pick cleanly, please mention the necessary changes in the pull request description in the next section.

Creating the Backport Pull Request

The backport pull-request may be created via CLI tools, or alternatively you can use the GitHub web interface to achieve these steps.

Via GitHub Web Interface

  1. Push your backports branch to your fork of the Cilium repo.

    $ git push -u <remote_for_your_fork> HEAD

  2. Create a new PR from your branch towards the feature branch you are backporting to. Note that by default Github creates PRs against the main branch, so you will need to change it. The title and description for the pull request should be based upon the vRELEASE-backport-YYYY-MM-DD.txt file that was generated by the scripts above.

    Note

    The vRELEASE-backport-YYYY-MM-DD.txt file will include:

    Once this PR is merged, a GitHub action will update the labels of these PRs:
```upstream-prs
AAA BBB
```

    The upstream-prs tag is required, so add it if you manually write the message.

  3. Label the new backport PR with the backport label for the stable branch such as backport/X.Y as well as kind/backports so that it is easy to find backport PRs later.

  4. Mark all PRs you backported with the backport pending label backport-pending/X.Y and clear the needs-backport/X.Y label. This can be done with the command printed out at the bottom of the output from the start-backport script above (GITHUB_TOKEN needs to be set for this to work).

Running the CI Against the Pull Request

To validate a cross-section of various tests against the PRs, backport PRs should be validated in the CI by running all CI targets. This can be triggered by adding a comment to the PR with exactly the text /test-backport-x.x, where x.x is the target version as described in Triggering Platform Tests. The comment must not contain any other characters.

After the Backports are Merged

After the backport PR is merged, the GH workflow “Call Backport Label Updater” should take care of marking all backported PRs with the backport-done/X.Y label and clear the backport-pending/X.Y label(s). Verify that the workflow succeeded by looking here.

Backporting Guide for Others

Original Committers and Reviewers

Committers should mark PRs needing backport as needs-backport/X.Y, based on the backport criteria. It is up to the reviewers to confirm that the backport request is reasonable and, if not, raise concerns on the PR as comments. In addition, if conflicts are foreseen or significant changes to the PR are necessary for older branches, consider adding the backport/author label to mark the PR to be backported by the author.

At some point, changes will be picked up on a backport PR and the committer will be notified and asked to approve the backport commits. Confirm that:

  1. All the commits from the original PR have been indeed backported.

  2. In case of conflicts, the resulting changes look good.