Registry HA

To be able to run fully offline, MetalK8s comes with its own registry serving all necessary images used by its containers. This registry container sits on the Bootstrap node.

With a highly available registry, container images are served by multiple nodes, which means the Bootstrap node can be lost without impacting the cluster. It allows pods to be scheduled, even if the needed images are not cached locally.

Note

This procedure only talk about registry HA as Bootstrap HA is not supported for the moment, so it’s only a part of the Bootstrap functionnaly. Check this ticket for more informations https://github.com/scality/metalk8s/issues/2002

Prepare the node

To configure a node to host a registry, a repository pod must be scheduled on it. This node must be part of the MetalK8s cluster and no specific roles or taints are needed.

All ISOs listed in the archives section of /etc/metalk8s/bootstrap.yaml and /etc/metalk8s/solutions.yaml must be copied from the Bootstrap node to the target node at exactly the same location.

Deploy the registry

Connect to the node where you want to deploy the registry and run the following salt states

  • Prepare all the MetalK8s ISOs

    root@node-1 $ salt-call state.sls \
        metalk8s.archives.mounted \
        saltenv=metalk8s-2.11.0-dev
  • If you have some solutions, prepare the solutions ISOs

    root@node-1 $ salt-call state.sls \
        metalk8s.solutions.available \
        saltenv=metalk8s-2.11.0-dev
  • Deploy the registry container

    root@node-1 $ salt-call state.sls \
        metalk8s.repo.installed \
        saltenv=metalk8s-2.11.0-dev

Reconfigure the container engines

Containerd must be reconfigured to add the freshly deployed registry to its endpoints and so it can still pull images in case the Bootstrap node’s one is down.

From the Bootstrap node, run (replace <bootstrap_node_name> with the actual Bootstrap node name):

root@bootstrap $ kubectl exec -n kube-system -c salt-master \
   --kubeconfig=/etc/kubernetes/admin.conf \
   salt-master-<bootstrap_node_name> -- salt '*' state.sls \
   metalk8s.container-engine saltenv=metalk8s-2.11.0-dev