psql-stack

PostgreSQL platform layer on top of CloudNativePG. Composes the CNPG operator, the cnpg-i-scale-to-zero plugin, the Atlas Operator (declarative schema migrations), a paired psql StorageClass + VolumeSnapshotClass that PSQLClusters and PSQLBranches default to.

This is the platform layer — it does not create any serving Postgres clusters. Per-app DBs live in PSQLCluster, ephemeral forks in PSQLBranch.

Design

• Paired StorageClass + VolumeSnapshotClass, both named psql. Snapshots only work when the snapshotter driver matches the underlying StorageClass provisioner, so the stack composes both with the same CSI driver value. PSQLClusters and PSQLBranches default spec.storage.class: psql (XRD default), so consumer manifests don't have to know the driver. Default driver/provisioner is ebs.csi.eks.amazonaws.com (EKS Auto Mode); override storageClass.provisioner + snapshotClass.driver together for non-EKS targets (kind, self-managed Longhorn, etc.).
• No NodePool / node-prep. Components run wherever the cluster's scheduler puts them. Auto Mode handles node provisioning end-to-end.

If you need replicated CoW storage (true block-level branches with delta-only economics), that's a separate concern — see aws-storage-stack for self-managed nodes that can host Longhorn or similar. The default psql-stack stays on the AWS-blessed Auto Mode path.

Components

Component	Default	Purpose
CNPG operator	always-on	The CNCF Postgres operator. CRDs include Cluster, Backup, Pooler, ScheduledBackup.
cnpg-i-scale-to-zero plugin	on (spec.scaleToZeroPlugin.enabled: true)	Auto-hibernates idle CNPG Clusters. Requires cert-manager (provided by aws-cert-stack).
Atlas operator	always-on	Declarative schema migrations via AtlasMigration / AtlasSchema CRDs.
StorageClass	on (spec.storageClass.enabled: true)	Named psql by default. Provisioner: ebs.csi.eks.amazonaws.com with type: gp3. PSQLCluster + PSQLBranch reference it as their default spec.storage.class.
VolumeSnapshotClass	on (spec.snapshotClass.enabled: true)	Named psql by default. Driver matches storageClass.provisioner. PSQLBranch references it for snapshot/fork.
HA mode	off (spec.ha.enabled: false)	When enabled: 3 replicas + topologySpreadConstraints by zone on CNPG, Atlas, S2Z plugin.

Prerequisites

• A working CSI driver on the cluster matching storageClass.provisioner. EKS Auto Mode provides ebs.csi.eks.amazonaws.com automatically. For other targets, override storageClass.provisioner (and the matching snapshotClass.driver) to whatever the target cluster has — e.g. hostpath.csi.k8s.io for kind, driver.longhorn.io for self-managed Longhorn.
• VolumeSnapshot CRDs + snapshot-controller (snapshot.storage.k8s.io). EKS Auto Mode ships the snapshot CRDs but not the cluster-wide snapshot-controller. Without one, the composed VolumeSnapshotClass is inert and PSQLBranch snapshots will never reach ReadyToUse. Install volume-snapshot-stack (also in this org) — it composes the upstream snapshot-controller via the piraeus-charts Helm chart and is the canonical CRD installer for the cluster.
• cert-manager (only when scaleToZeroPlugin.enabled — the plugin uses cert-manager Issuer+Certificate for its gRPC TLS). Provided by aws-cert-stack.

Stages

Stage 1: Default install

Deploy with all defaults. CNPG + Atlas + S2Z + a psql VolumeSnapshotClass for EBS.

apiVersion: hops.ops.com.ai/v1alpha1
kind: PSQLStack
metadata:
  name: psql
  namespace: default
spec:
  clusterName: my-cluster

Stage 2: Production posture

HA on; per-component value tweaks; team labels for cost allocation.

apiVersion: hops.ops.com.ai/v1alpha1
kind: PSQLStack
metadata:
  name: psql
  namespace: default
spec:
  clusterName: production-cluster
  namespace: cnpg-system
  labels:
    team: platform
  ha:
    enabled: true
    replicas: 3
    topologySpreadByZone: true
  atlasOperator:
    values:
      prewarmDevDB: true

Stage 3: Non-EKS cluster

Override the SC + VSC driver together (they must match for snapshots to work). Example: self-managed cluster running Longhorn.

apiVersion: hops.ops.com.ai/v1alpha1
kind: PSQLStack
metadata:
  name: psql
  namespace: default
spec:
  clusterName: edge
  helmProviderConfigRef:
    name: default
  storageClass:
    provisioner: driver.longhorn.io
    parameters:
      numberOfReplicas: "3"
  snapshotClass:
    driver: driver.longhorn.io

Stage 4: Opt out of the composed StorageClass

If the cluster already ships a suitable default StorageClass, disable composition and have PSQLCluster/PSQLBranch consumers set spec.storage.class explicitly.

apiVersion: hops.ops.com.ai/v1alpha1
kind: PSQLStack
metadata:
  name: psql
  namespace: default
spec:
  clusterName: shared-cluster
  helmProviderConfigRef:
    name: default
  storageClass:
    enabled: false

Stage 5: Local / no-snapshot cluster

For dev clusters without a snapshot-controller, disable the VSC composition. PSQLBranch won't function (it needs the VSC), but PSQLCluster still works.

apiVersion: hops.ops.com.ai/v1alpha1
kind: PSQLStack
metadata:
  name: psql
  namespace: default
spec:
  clusterName: local
  helmProviderConfigRef:
    name: default
  snapshotClass:
    enabled: false
  scaleToZeroPlugin:
    enabled: false

Spec Reference

Field	Type	Default	Description
clusterName	string	required	Target cluster name; default for helmProviderConfigRef.name, kubernetesProviderConfigRef.name, and label values
namespace	string	cnpg-system	Shared namespace for CNPG, S2Z plugin, and Atlas
labels	object	—	Custom labels merged with stack defaults
managementPolicies	string[]	["*"]	Crossplane management policies
helmProviderConfigRef.name	string	clusterName	Helm ProviderConfig name
helmProviderConfigRef.kind	enum	ProviderConfig	ProviderConfig or ClusterProviderConfig
kubernetesProviderConfigRef.name	string	clusterName	Kubernetes ProviderConfig name
kubernetesProviderConfigRef.kind	enum	ProviderConfig	Same as above
HA mode
ha.enabled	bool	false	Stack-wide HA toggle
ha.replicas	int	3	Replica count for HA-able platform components
ha.topologySpreadByZone	bool	true	Add topologySpreadConstraint with topologyKey=topology.kubernetes.io/zone, maxSkew=1, whenUnsatisfiable=ScheduleAnyway
CNPG operator
cnpg.name	string	cloudnative-pg	Helm release name
cnpg.chartVersion	string	0.27.1	CNPG Helm chart version (tracks CNPG 1.29.x)
cnpg.values	object	—	Helm values merged with chart defaults
cnpg.overrideAllValues	object	—	Helm values that replace all defaults
Scale-to-zero plugin
scaleToZeroPlugin.enabled	bool	true	Install the plugin (zero-cost when no Cluster opts in)
scaleToZeroPlugin.version	string	v0.1.7	Plugin release tag
scaleToZeroPlugin.namespace	string	shared namespace	Override
Atlas operator
atlasOperator.name	string	atlas-operator	Helm release name
atlasOperator.namespace	string	shared namespace	Override
atlasOperator.values	object	—	Helm values merged with chart defaults
atlasOperator.overrideAllValues	object	—	Helm values that replace all defaults
Storage class
storageClass.enabled	bool	true	Compose the StorageClass
storageClass.name	string	psql	StorageClass name (PSQLCluster + PSQLBranch reference this)
storageClass.provisioner	string	ebs.csi.eks.amazonaws.com	CSI driver name. Must match snapshotClass.driver
storageClass.reclaimPolicy	enum	Delete	Delete or Retain
storageClass.volumeBindingMode	enum	WaitForFirstConsumer	Immediate or WaitForFirstConsumer
storageClass.allowVolumeExpansion	bool	true	Online PVC expansion (CNPG resizes via the same field on its Cluster CR)
storageClass.parameters	object	{type: gp3}	Provisioner-specific parameters
Snapshot class
snapshotClass.enabled	bool	true	Compose the VolumeSnapshotClass
snapshotClass.name	string	psql	VolumeSnapshotClass name (PSQLBranch references this)
snapshotClass.driver	string	ebs.csi.eks.amazonaws.com	CSI driver. Must match storageClass.provisioner
snapshotClass.deletionPolicy	enum	Delete	Delete or Retain
snapshotClass.parameters	object	—	Driver-specific parameters

Composed Resources

Resource	Kind	When
cloudnative-pg	helm.m.crossplane.io/Release	always
atlas-operator	helm.m.crossplane.io/Release	always
9× <name>-s2z-*	kubernetes.m.crossplane.io/Object	scaleToZeroPlugin.enabled: true
<name>-storageclass	kubernetes.m.crossplane.io/Object	storageClass.enabled: true
<name>-volumesnapshotclass	kubernetes.m.crossplane.io/Object	snapshotClass.enabled: true
Various Usage	protection.crossplane.io/Usage	when both ends Ready (deletion ordering)

Dependencies

Kind	Package	Version
Function	crossplane-contrib/function-auto-ready	>=v0.6.2
Provider	crossplane-contrib/provider-helm	>=v1
Provider	crossplane-contrib/provider-kubernetes	>=v1

Development

make render             # Render all examples
make validate           # Validate against Crossplane schemas
make test               # KCL render tests (assert composed resource shapes)
make build              # Build the package
make render:standard    # Render a single example

License

Apache-2.0