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Avoiding required stops

Required stops are any changes to GitLab components or dependencies that result in the need to upgrade to and stop at a specific major.minor version when upgrading GitLab.

While Development maintains a maintainenance policy that results in a three-release (3 month) backport window - GitLab maintains a much longer window of version support that includes the current major version, as well as the two previous major versions. Based on the schedule of previous major releases, GitLab customers can lag behind the current release for up to three years and still expect to have support for upgrades.

For example, a GitLab user upgrading from GitLab 14.0.12 to GitLab 16.1, which is a fully supported upgrade path, may have the following required stops: 14.3.6, 14.9.5, 14.10.5, 15.0.5, 15.1.6, 15.4.6, and 15.11.11 before upgrading to the latest 16.1.z version.

Past required stops have not been discovered for months after their introduction, often as the result of extensive troubleshooting and assistance from Support Engineers, Customer Success Managers, and Development Engineers as users upgrade across greater than 1-3 minor releases.

Wherever possible, a required stop should be avoided. If it can't be avoided, the required stop should be aligned to a scheduled required stop.

Scheduled required stops are often implemented for the previous major.minor release just prior to a major version release in order to accomodate multiple planned deprecations and known breaking changes.

Additionally, as of GitLab 16, we have introduced scheduled major.minor required stops:

During GitLab 16.x, we are scheduling two or three required upgrade stops.

We will give at least two milestones of notice when we schedule a required upgrade stop. The first planned required upgrade stop is scheduled for GitLab 16.3. If nothing is introduced requiring an upgrade stop, GitLab 16.3 will be treated as a regular upgrade.

Causes of required stops

Inaccurate assumptions about completed migrations

The majority of required stops are due to assumptions about the state of the data model in a given release, usually in the form of interdependent database migrations, or code changes that assume that schema changes introduced in prior migrations have completed by the time the code loads.

Designing changes and migrations for backwards compatibility between versions can mitigate stop concerns with continuous or "zero-downtime" upgrades. However, the contract phase will likely introduce a required stop when a migration/code change is introduced that requires that background migrations have completed before running or loading.

WARNING: If you're considering adding or removing a migration, or introducing code that assumes that migrations have completed in a given release, first review the database-related documentation on required stops.

Examples

  • GitLab 12.1: Introduced a background migration changing merge_status in MergeRequests depending on the state value. The state attribute was removed in 12.10. It took until 13.6 to document the required stop.
  • GitLab 13.8: Includes a background migration to deal with duplicate service records. In 13.9, a unique index was applied in another migration that depended on the background migration completing. Not discovered/documented until GitLab 14.3
  • GitLab 14.3: Includes a potentially long-running background migration against merge_request_diff_commits that was foregrounded in 14.5. This change resulted in extensive downtime for users with large GitLab installations. Not documented until GitLab 15.1
  • GitLab 14.9: Includes a batched background migration for namespaces and projects that needs to finish before another batched background migration added in 14.10 executes, forcing a required stop. The migration can take hours or days to complete on large GitLab installations.

Additional details as well as links to related issues and merge requests can be found in: Issue: Put in place measures to avoid addition/proliferation of GitLab upgrade path stops

Removal of code workarounds and mitigations

Similar to assumptions about the data model/schema/migration state, required major.minor stops have been introduced due to the intentional removal of code implemented to workaround previously discovered issues.

Examples

  • GitLab 13.1: A security fix in Rails 6.0.3.1 introduced a CSRF token change (causing a canary environment incident). We introduced code to maintain acceptance of previously generated tokens, and removed the code in 13.2, creating a known required stop in 13.1.
  • GitLab 15.4: Introduces a migration to fix an inaccurate expires_at timestamp for job artifacts that had been mitigated in code since GitLab 14.9. The workaround was removed in GitLab 15.6, causing 15.4 to be a required stop.

Deprecations

Deprecations, particularly breaking changes can also cause required stops if they introduce long migration delays or require manual actions on the part of GitLab administrators.

These are generally accepted as a required stop around a major release, either stopping at the latest major.minor release immediately proceeding a new major release, and potentially the lastest major.0 patch release, and to date, discovered required stops related to deprecations have been limited to these releases.

Examples

Examples of deprecations are too numerous to be listed here, but can found in the deprecations and removals by version as well as the version-specific upgrading instructions, version-specific changes for the GitLab package (Omnibus), and GitLab chart upgrade notes.

Further reading