Availability Group

The availabilityGroup topology deploys an Always-On Availability Group: a set of SQL Server replicas joined into a quorum-based cluster with automatic failover. It maps to the operator's MSSQLAvailabilityGroup resource.

Clients write to the <name>-primary Service and can read from the <name>-replicas Service. When the primary fails, the operator promotes a secondary and the Services follow the new roles.

Requirements

• At least 2 replicas (3 is the recommended minimum for a healthy quorum).
• An edition that supports Always-On: Developer, Standard, Enterprise, or EnterpriseCore. Express is not supported.

Example

apiVersion: core.openeverest.io/v1alpha1
kind: Instance
metadata:
  name: example-ag
spec:
  providerRef:
    name: mssql
  version: "2022"
  topology:
    type: availabilityGroup
    parameters:
      # synchronous (zero data loss) or asynchronous (lower latency)
      availabilityMode: synchronous
      # all | readOnly | no — whether secondaries accept read traffic
      readableSecondaries: all
  components:
    engine:
      replicas: 3
      resources:
        limits:
          cpu: "2"
          memory: 4Gi
      storage:
        size: 20Gi
      parameters:
        edition: Developer
        # Reference a dockerconfigjson Secret you created in the namespace.
        imagePullSecrets:
          - ghcr-pull-secret

Topology parameters

Set under spec.topology.parameters:

Parameter	Values	Default	Description
availabilityMode	synchronous, asynchronous	synchronous	synchronous guarantees zero data loss; asynchronous favors lower latency.
readableSecondaries	all, readOnly, no	all	Whether secondary replicas serve read traffic via the <name>-replicas Service.

How replication works

Connecting

Write to the <name>-primary Service and read from <name>-replicas. See Connecting for details and connection strings.

See also

• Standalone — the single-instance topology.
• Operator: Always-On Availability Groups.