Database cluster for container registry (initial request)

This is a follow-up from https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/10109.

The new Container Registry being built by @jdrpereira and @hswimelar in gitlab-org&2313 (closed) is going to need a Postgres database. As discussed in https://gitlab.com/gitlab-com/gl-infra/infrastructure/-/issues/10109, this is going to be logically separate from the GitLab database and should live in a separate Postgres cluster on GitLab.com.

This issue is about making this Postgres cluster available to be used in staging and production environments.

Details

• Estimated database size: A few hundred GBs per gitlab-org/container-registry#61 (comment 379740915)
• Estimated request/database rates: gitlab-org/container-registry#94 (closed)
• HA/DR requirements: Same as GitLab.com main database
• For starters, container registry will only connect to the primary (no read-only balancing for starters, likely comes in later)
• We are going to start with PostgreSQL 12 already
• Background read for container registry's online garbage collection: gitlab-org/container-registry#199 (closed)

Related issues

• Discussion about deployment-side of this is delivery#1058 (closed)
• Database team looking at the database schema design (with partitioning/scalability in mind) gitlab-org&4073 (closed)

Proposed timeline

• Staging: Postgres cluster available by October 2020
• Production: Postgres cluster available by mid November 2020