Customize High Availability

Achieve high availability using the prod profile

High availability designs follow three main principles:

  • Elimination of single points of failure
  • Fault detection
  • Reliable failover points

Verrazzano provides a means to eliminate single points of failure among critical Verrazzano components. This is accomplished by increasing replica counts, anti-affinity rules, and implementing replicated data for components that rely on MySQL and OpenSearch.

The ha.yaml file illustrates how the prod profile can be extended to configure a highly available Verrazzano installation. The increased replica counts, along with the anti-affinity rules inherited from the prod profile, ensure that the pods of each component are distributed across the Kubernetes cluster nodes. MySQL and OpenSearch are configured to replicate data among replicas to avoid data loss.

The ha-oci-ccm.yaml file configures a highly available Verrazzano installation on OCNE.

The ha-ext-lb.yaml file configures a highly available Verrazzano installation using external load balancers.

Fault detection is managed natively by using Kubernetes Services and Istio VirtualServices that detect failed pods and route traffic to the remaining replicas.

MySQL and OpenSearch provide reliable failover points for the replicated data.

The result of these measures would be no loss of service if a cluster node became unavailable. For more information regarding node failure and recovery, read the Node Failure Guide.

When using the ha.yaml file, consider the following:

  • It does not ensure a fault-tolerant environment. Your applications still must be designed and implemented as highly available.
  • Running additional replicas of components will increase resource requirements. At least four CPUs, 100 GB disk storage, and 64 GB RAM available on the Kubernetes worker nodes is required.
  • Additional customizations may be required for your environment, including other customizations described in individual sections.

For the expected behavior of the MySQL Component in a highly available environment, see Customize Keycloak and MySQL.

Follow these best practices for a highly available Verrazzano installation:

  • Size your Kubernetes cluster according to your node failure tolerance and workload requirements.
  • Set the default Storage Class to one with a VolumeBindingMode of WaitForFirstConsumer. This is important for being able to recover from an Availability Domain or zone failure.
  • Set the replica counts to values that correspond to your node failure tolerance.

To install the example high availability configuration using the Verrazzano CLI:

$ vz install -f

Using the Verrazzano CLI, install the example high availability configuration on OCNE as follows:

 $ vz install -f

Using the Verrazzano CLI, install the example high availability configuration with external load balancers as follows:

$ vz install -f

Upgrade recommendations

An OKE in-place upgrade scales the cluster to N-1 nodes, where N is the original number of nodes, so you must scale the cluster back to N. This will start a new replacement node using the new node pool. For more information on in-place upgrades, see Performing an In-Place Worker Node Kubernetes Upgrade by Updating an Existing Node Pool.