PluginPresets

A PluginPreset is used to configure Plugins for a set of Clusters. This allows administrators to define standard configurations for Clusters in the same environment or with similar requirements. Greenhouse will create Plugins based on the PluginPreset for each Cluster that matches the specified selector.

Example PluginPreset Spec

apiVersion: greenhouse.sap/v1alpha1
kind: PluginPreset
metadata:
  name: perses-preset
  namespace: example-organization
spec:
  clusterOptionOverrides:
    - clusterName: example-cluster
      overrides:
      - name: perses.serviceMonitor.selfMonitor
        value: true
      - name: perses.serviceMonitor.labels
        value:
          plugin: kube-monitoring
  clusterSelector:
    matchExpressions:
    - key: cluster-type
      operator: In
      values:
      - observability
  deletionPolicy: Delete
  plugin:
    optionValues:
    - name: perses.sidecar.enabled
      value: true
    - name: perses.ingress.host
      expression: |
        "perses.${global.greenhouse.clusterName}.example.com"        
    pluginDefinitionRef:
      kind: ClusterPluginDefinition
      name: perses
    releaseName: perses
    releaseNamespace: kube-monitoring

Writing a PluginPreset Spec

.spec.plugin is the template for the Plugins that will be created for each matching Cluster. This field has the same structure as the PluginSpec. Only .spec.clusterName is not allowed in the PluginPreset’s Plugin template, as the Cluster name is determined by the matching Clusters.

ℹ️ A non-existing PluginDefinition can be referenced in the PluginPreset. The PluginPreset will be reconciled once the PluginDefinition is created. This allows rolling out new PluginDefinitions via a Catalog together with the PluginPresets that reference them.

spec:
  plugin:
    optionValues:
    - name: perses.sidecar.enabled
      value: true
    pluginDefinitionRef:
      kind: ClusterPluginDefinition
      name: perses
    releaseName: perses
    releaseNamespace: kube-monitoring

.spec.clusterSelector is a required field that specifies the label selector used to list the Clusters for which Plugins will be created based on this PluginPreset.

spec:
  clusterSelector:
    matchExpressions:
    - key: cluster-type
      operator: In
      values:
      - observability

| ⚠️ Changing the clusterSelector may result in the creation or deletion of Plugins for Clusters that start or stop matching the selector. |

.spec.clusterOptionOverrides is an optional field that can be used to provide per-Cluster overrides for the Plugin’s OptionValues. This can be used to customize the configuration of the Plugin for specific Clusters.

spec:
  clusterOptionOverrides:
    - clusterName: example-cluster
      overrides:
      - name: perses.serviceMonitor.selfMonitor
        value: true

.spec.deletionPolicy is an optional field that specifies the behaviour when a PluginPreset is deleted. The possible values are Delete and Retain. If set to Delete (the default), all Plugins created by the PluginPreset will also be deleted when the PluginPreset is deleted. If set to Retain, the Plugins will remain after the PluginPreset is deleted or if the Cluster stops matching the selector.

CEL Expressions in OptionValues

PluginPresets support CEL (Common Expression Language) expressions in optionValues. When pluginPreset.expressionEvaluationEnabled is enabled, expressions are evaluated during PluginPreset reconciliation and the resulting Plugin contains only the resolved values with no expression fields remaining.

Expressions use the ${...} syntax to reference dynamic values:

spec:
  plugin:
    optionValues:
    - name: app.hostname
      expression: |
        "myapp.${global.greenhouse.clusterName}.example.com"        

When this PluginPreset creates a Plugin for a cluster named cluster-a, the Plugin will contain:

spec:
  optionValues:
  - name: app.hostname
    value: "myapp.cluster-a.example.com"

Available Variables

ℹ️ global.greenhouse.metadata.* values are derived from cluster labels prefixed with metadata.greenhouse.sap/. For example, the label metadata.greenhouse.sap/region: eu-de-1 becomes available as global.greenhouse.metadata.region.

Examples

Hostname per cluster:

- name: ingress.host
  expression: |
    "service.${global.greenhouse.clusterName}.example.com"    
# Result for cluster "cluster-a": "service.cluster-a.example.com"

Using cluster metadata:

- name: ingress.host
  expression: |
    "service.${global.greenhouse.metadata.region}.example.com"    
# Result: "service.eu-de-1.example.com"
# Requires label metadata.greenhouse.sap/region on the cluster

Combining variables:

- name: app.fqdn
  expression: |
    "${global.greenhouse.clusterName}-${global.greenhouse.organizationName}"    
# Result for cluster "cluster-a" in org "my-org": "cluster-a-my-org"

Expressions in ClusterOptionOverrides

Expressions can also be used in clusterOptionOverrides. Overrides are merged before expression evaluation, so override expressions are also resolved:

spec:
  plugin:
    optionValues:
    - name: app.mode
      value: "standard"
  clusterOptionOverrides:
    - clusterName: special-cluster
      overrides:
      - name: app.hostname
        expression: |
          "special.${global.greenhouse.metadata.region}.example.com"          

ℹ️ Expressions are evaluated in PluginPresets when pluginPreset.expressionEvaluationEnabled is enabled. Standalone Plugin expressions are still supported (deprecated) and may be evaluated by the Plugin controller depending on feature flags.

Feature Flag

CEL expression evaluation is disabled by default. To enable it, set pluginPreset.expressionEvaluationEnabled: true in the Greenhouse feature flags ConfigMap.

# greenhouse-feature-flags ConfigMap
apiVersion: v1
kind: ConfigMap
metadata:
  name: greenhouse-feature-flags
  namespace: greenhouse
data:
  pluginPreset: |
    expressionEvaluationEnabled: true    

Next Steps

• Managing Plugins for multiple clusters
• Plugin reference
• PluginDefinition reference