GitLab Housekeeper - automating merge requests

Summary

This blueprint documents the philosophy behind the “GitLab Housekeeper” gem which was introduced in https://gitlab.com/gitlab-org/gitlab/-/merge_requests/139492 and has already been used to create many merge requests.

The tool should be used to save developers from mundane repetitive tasks that can be automated. The tool is scoped to any task where a developer needs to create a straightforward merge request and is known ahead of time.

This tool should be useful for at least the following kinds of mundane MRs we create:

1. Remove a feature flag after X date
2. Remove an unused index where the unused index is identified by some automation
3. Remove an ignore_column after X date (part of renaming/removing columns multi-step procedure)
4. Populate sharding keys for organizations/cells on tables that are missing a sharding key

Motivation

We’ve observed there are many cases where developers are doing a lot of manual work for tasks that are entirely predictable and automatable. Often these manual tasks are done after waiting some known period of time. As such we usually create an issue and set the future milestone. Then in the future the developer remembers to followup on that issue and opens an MR to make the manual change.

The biggest examples we’ve seen lately are:

1. Feature flag removal: https://gitlab.com/groups/gitlab-org/-/epics/5325. We have many opportunities for automation with feature flags but this blueprint focuses on removing the feature flag after it’s fully rolled out. A step that is often forgotten leading to growing technical debt.
2. Removing duplicated or unused indexes in Postgres: https://gitlab.com/gitlab-org/gitlab/-/issues/385701. For now we’re developing automation that creates issues and assigns them to groups to follow up and manually open MRs to remove them. This blueprint would take it a step further and the automation would just create the MRs to remove them once we have identified them.
3. Removing out of date ignore_column references: https://docs.gitlab.com/ee/development/database/avoiding_downtime_in_migrations.html#removing-the-ignore-rule-release-m2 . For now we leave a note in our code telling us the date it needs to be removed and often create an issue as a reminder. This blueprint proposes that automation just reads this note and opens the MR to remove it after the date.
4. Adding and backfilling sharding keys for organizations for Cells: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/133796. The cells architecture depends on all tables having a sharding key that is attributed to an organization. We will need to backfill this for ~300 tables. Much of this will be repetitive and mundane work that we can automate provided that groups just identify what the name of the sharding key should be and how we will backfill it. As such we can automate the creation of MRs that guess the sharding key and owning groups can check and correct those MRs. Then we can automate the MR creation for adding the columns and backfilling the data. Some kind of automation like this will be necessary to finish this work in a reasonable timeframe.

Goals

1. Identify the common tasks that take development time and automate them.
2. Focus on MR creation rather than issue creation as MRs are the results we want and issues are a process for reminding us to get those results.
3. Improve developer job satisfaction by knowing that automation is doing the busy work while we get to do the challenging and creative work.
4. Developers should be encouraged to contribute to the automation framework when they see a pattern rather than documenting the manual work for future developers to do it again.
5. Automation MRs should be very easily identified and reviewed and merged much more quickly than other MRs. If our automation MRs cause too much effort for reviewers we maybe will outweigh the benefits. This might mean that some automations get disabled when they are just noisy.

Solution

The GitLab Housekeeper gem should be used to automate creation of mundane merge requests.

Using this tool reflects our bias for action subvalue. As such, developers should preference contributing a new keep over the following:

1. Documenting a process that involves creating several merge requests over a period of time
2. Setting up periodic reminders for developers (in Slack or issues) to create some merge request

The keeps may sometimes take more work to implement than documentation or reminders so judgement should be used to assess the likely time savings from using automation. The gitlab-housekeeper gem will evolve over time with many utilities that make it simpler to contribute new keeps and it is expected that over time the cost to implementing a keep should be small enough that we will mostly prefer this whenever developers need to do a repeatable task more than a few times.

Design and implementation details

The key details for this architecture is:

1. The design of this tool is like a combination of rubocop -a and Renovate bot. It extends on rubocop -a to understand when things need to be removed after certain deadlines as well as creating a steady stream of manageable merge requests for the reviewer rather than leaving those decisions to the developer. Like the renovate bot it attempts to create MRs periodically and assign them to the right people to review.
2. The keeps live in the GitLab repo which means that there are no dependencies to update and the keeps can use code inside the GitLab codebase.
3. The script can be run locally by a developer or can be run periodically in some automated way.
4. The keeps are able to use any data sources (eg. local code, Prometheus, Postgres database archive, logs) needed to determine whether and how to make the change.

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