Migrate Redis Helm releases away from Bitnami

Overview

Bitnami will stop updating their redis container image on August 28th (see announcement), they will only provide a non-versioned latest Bitnami Secure Image for it instead, only suitable for dev purposes. So it needs to be replaced before then.

While their redis Helm chart will continue to be maintained publicly, its future remains uncertain and we wouldn't want to risk having to replace it on short notice again.

We use the Bitnami Redis chart in several places:

• for Redis cache deployments in gstg and gprd
• for Sentry
• for the ops.gitlab.net instance (built-in GitLab Helm chart dependency)
• for Atlantis

Proposed plan of action

• Redis cache in gstg/gprd:
  • short term: replace image refs to use docker.io/bitnamilegacy/redis instead
  • long term: TBD
• Sentry: see #27266 (closed)
• ops.gitlab.net: migrate to Memorystore?
• Atlantis: disable Redis to use the default local BoltDB file instead for MR/env locks

Exit Criteria

• The Redis cache instances in gstg and gprd no longer use the Bitnami Helm chart or images gitlab-com/gl-infra/data-access/durability/team#246 (closed)
• Sentry no longer use the Bitnami Helm chart or images
• ops.gitlab.net uses Memorystore instead of a Redis deployment in k8s
• Atlantis uses BoltDB instead of Redis