config-brancher

README

config-brancher

This tool is intended to make the process of branching and duplicating configuration for the CI Operator easy across many repositories.

What it does

The tool has two main modes of operations. The first mode is mirroring the CI Operator configuration from the branch where the active development occurs (such as main) to future release branches.

In the second mode, the tool is used to "bump" the configuration file versions, retargeting the configuration for the current development branch to the next version during the code freeze.

In both modes, it also enforces the basic promotion destination consistency.

Why it exists

The tool allows the users to only maintain a single CI Operator configuration file: the one for main development branch. The changes done in this file will then be automatically propagated to future release branches, reducing the surface for omissions and mistakes.

In the bump mode, the tool allows Test Platform to automatically perform the CI configuration changes on code freeze ( a.k.a "branch cut").

How it works

The tool iterates over all ci-operator config files in openshift/release, and it selects a set of repositories to operate on by looking at which are actively promoting images into a specific OpenShift release, provided by --current-release. Branches of repos that actively promote to this release are considered to be the dev branches.

Once the tool selects the set of configurations to operate on, it does one of two actions: Mirror the configuration out, or bump the configuration files.

Mirroring configuration

In the mirror configuration mode, it copies the development branch configuration to all branches for the provided --future-release values. The development branch version is not changed. Since this results in both the development branch and one of the release branches promoting to the same release ImageStream, promotion is disabled in the release branch for the version which matches that in the promotion stanza of the development branch. This ensures only one branch feeds that release ImageStream.

Bumping configuration

In the bumping mode, it moves the development branch to promote to the version in the --bump flag, enabling the promotion in the release branch that used to match the dev branch version and disabling promotion in the release branch that now matches the dev branch version.

How is it deployed

In the mirroring mode, the tool is executed regularly in the periodic-prow-auto-config-brancher job (definition) as a part of the autoconfigbrancher tool.

During the code freeze event, the tool is used manually in the bump mode,

Example

During the development of the OCP version 4.X, the components are expected to have the following configuration files in the openshift/release repository:

ci-operator/config/org/repo/org-repo-master.yaml         # Main development branch, promotes to OCP 4.X
ci-operator/config/org/repo/org-repo-release-4.X.yaml    # Release branch for OCP 4.X, promotes nowhere
ci-operator/config/org/repo/org-repo-release-4.X+1.yaml  # Release branch for OCP 4.X+1, promotes to OCP 4.X+1

The users are expected to only maintain the org-repo-master.yaml file. In the mirroring mode, the tool propagates any changes done in that file to both org-repo-release-4.X.yaml and org-repo-release-4.X+1.yaml files, making sure that these branches will eventually get the same CI treatment after they become actively used.

At 4.X code freeze, the tool will be executed in the bump mode. It will "retarget" the org-repo-master.yaml file to promote to OCP 4.X+1, make org-repo-release-4.X.yaml promote to OCP 4.X and disable promotion in the org-repo-release-4.X+1.yaml file.