Does quay operator support geo-replication?

Environment

• Red Hat Quay
  • 3.6
  • 3.7
• Red Hat OpenShift Container Platform
  • 4.x

Issue

• Does Red Hat have geo-replication enabled for operator deployed quay clusters?

Resolution

• The quay operator currently does not support geo-replication for versions below 3.7.0. However, the This content is not included.new feature request is released and one can leverage the geo-replication deployments of Quay among multiple clusters from Quay 3.7.0 onward.

Root Cause

• The problem with geo-replication in older versions is that it requires several prerequisites:

  1. All Quay instances need to have access to all storage engines. That means instances from DC 1 need to have access to storage from both DC 1 and DC 2, same goes for instances from DC 2.

  2. All Quay instances need exactly the same entry point. Otherwise, authentication issues might occur.

  3. All Quay instances must have access to the same database engine because replication is done by Quay workers and not the storage engine.

• Because of this, to get Quay to run in a geo-replicated environment, one needs to set almost all components of the QuayRegistry CRD to unmanaged.

• The situation complicates further when Clair is added. Another problem is syncing configuration changes between DCs. If parameters in DC 1 change, the same change to the config.yaml file in DC 2 should be applied. This cannot be done automatically today and is prone to human error.

• Finally, there arises a question about upgrades. If a database schema is changed, which cluster has precedence in the upgrade procedure? Usually, db schema upgrades require a shutdown of Quay but one cannot do an upgrade from two places at once. One can only upgrade the schema from a single instance.

• Because of the above-discussed issues, Red Hat cannot provide support Geo-replicated environment on OpenShift for earlier versions of Quay.

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