KEP-0000: Anago to Krel Migration

Implementation History
STABLE Implemented
Created 2020-09-22
Latest v1.20
Ownership
Owning SIG
SIG Release
Primary Authors
@saschagrunert

Anago to Krel Migration

Moving away from running bash in production in k/release

Objectives

This roadmap defines a strategy for achieving two primary goals: migrating exchangeable bits of bash code within anago to krel and creating a Golang native replacement for anago.

Milestones

  1. Complete the code migration
  2. Have a minimum working krel stage
  3. Have a minimum working krel release
  4. Remove/swap out Anago in a simple way, after completing the preceding steps

The scope and implementation details of Milestones 2-4 will become clearer as work on Milestone 1 proceeds.

Creating new features for krel is out of scope.

First Milestone: Complete the Migration Effort

Anago is still the main bash script running in GCB, which right now calls out to krel if necessary. Many parts of the bash-based source code in k/release have already been transferred to krel (golang), whereas we directly remove the bash-based parts from the repository after each refactoring iteration.

This milestone focuses on reducing technical debt in k/release by migrating the remaining bash code into refactored golang-based implementations. This effort will lead to higher quality and provide a stable foundation for future feature developments. By “stable,” we mean that making changes will not break the entire system.

This migration will not interrupt our ability to cut releases.

Open Issues

The list of currently outlined issues, with assignees (release managers) where established:

All four issues can be worked on in parallel. This is not a comprehensive list: There are still parts in Anago that can be ported from bash and that are not part of any issue yet.

Acceptance Criteria

  • All issues currently open will be resolved (#1534 , #1536 , #1446 , #1459 )
  • New code is unit-tested and code-reviewed (logical paths, not line coverage)
  • Direct use of the new Golang source code in production

Second Milestone: Introduce krel stage/release

In parallel to the ongoing migration (first milestone) we will introduce new krel stage and krel release subcommands. The plan is to re-evaluate the current functionality within anago and build a declarative approach of cutting releases. We can re-use the already migrated parts as well as using the existing logic in anago as guidance for the necessary feature set of krel stage/release.

Open Issues

The list of currently outlined issues, with assignees (release managers) where established:

Risks

The highest risk during the migration is that we end-up in a state where we break the current functionality. This would mean that we cannot build releases any more. Immediate fixing and incremental testing between the releases should minimize this risk.

Quality/Test Plan

Merge changes to the main branch from user fork/branch as per normal community PR process. Feature branches will not be used.

Anago-replacement features must be behind a feature gate, initially ensuring they are only run in ‘mock’ mode.

Merged features can be tested in production at any time so long as they are only triggered from a mock stage or mock release or mock notify.

Non-mock testing will occur only during a release cycle’s alpha period. This gives initial test ability for non-mock paths in Sep/Oct 2020 and again in Jan/Feb 2021. Beyond Feb 2021, we will need to re-evaluate testing based on future circumstances.

During alpha periods we can A/B test, eg: build alpha.1 with Anago and immediately after build alpha.2 with krel. Compare the results.