Backporting process

Backport Criteria

Committers may nominate PRs that have been merged into master 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

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

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. The scripts referred to below need to be run on Linux, they do not work on macOS. You can use the cilium dev VM for this, but 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
    
  2. Make sure you have a GitHub developer access token with the public_repos scope available. For details, see contrib/backporting/README.md

  3. 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 No Python Downloads
    PyGithub No pip3 install PyGithub
    Github hub CLI No N/A (OS-specific)

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). If any PRs contain labels such as backport-pending/X.Y, ensure that the backport for that PR have been merged and if so, change the label to backport-done/X.Y.

Creating the backports branch

  1. 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.

  2. Cherry-pick the commits using the master 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.

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

  4. Push your backports branch to cilium repo.

    $ git push -u origin HEAD
    

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 command-line tools

These steps require all of the tools described in the One-time setup section above. It pushes the git tree, creates the pull request and updates the labels for the PRs that are backported, based on the vRELEASE-backport-YYYY-MM-DD.txt file in the current directory.

# contrib/backporting/submit-backport

Via GitHub web interface

  1. Create a new PR from your branch towards the feature branch you are backporting to. Note that by default Github creates PRs against the master 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, you can update the PR labels via:
    ```upstream-prs
    $ for pr in AAA BBB ; do contrib/backporting/set-labels.py $pr done VVV; done
    ```
    

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

  2. 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.

  3. Mark all PRs you backported with the backport pending label backport-pending/X.Y and clear the needs-backport/vX.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. The comment must not contain any other characters.

After the backports are merged

After the backport PR is merged, mark all backported PRs with backport-done/X.Y label and clear the backport-pending/X.Y label(s). If the backport pull request description was generated using the scripts above, then the full command is listed in the pull request description.

$ for pr in 12589 12568; do contrib/backporting/set-labels.py $pr done 1.8; done

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.

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.

Merger

When merging a backport PR, set the labels of the backported PRs to done. Typically, backport PRs include a line on how do that. E.g.,:

$ for pr in 12894 12621 12973 12977 12952; do contrib/backporting/set-labels.py $pr done 1.8; done