EngineClass configuration inheritance

Share Engine settings while allowing per-Engine overrides.

A FireboltEngineClass provides reusable defaults to Engines in the same namespace. Set FireboltEngine.spec.engineClassRef to the class name.

Values resolve in this order:

1. The Engine value
2. The namespace FireboltEnginePreset value, when one object exists
3. The referenced EngineClass value
4. The Firebolt Operator default

An EngineClass is namespaced because its pod template can reference namespaced resources such as ServiceAccounts, Secrets, ConfigMaps, and persistent volume claims.

Pod template precedence

The Engine template overrides Preset, and Preset overrides the class, for conflicting scalar values. Collection behavior depends on the field:

Field	Resolution
serviceAccountName	Engine, then Preset, then class
nodeSelector	Maps merge; Engine keys win over Preset keys, which win over class keys
tolerations, topologySpreadConstraints, imagePullSecrets	Class entries, then Preset entries, then Engine entries
affinity, pod securityContext	Engine value replaces Preset, which replaces class, when set
labels and annotations	Maps merge; Engine keys win; firebolt.io/ keys are reserved
volumes	Class entries, then Preset entries, then Engine entries; Firebolt Operator volume names are reserved
init containers and sidecars	Class entries, then Preset entries, then Engine entries
Engine container image and pull policy	Engine, then Preset, then class, then Firebolt Operator default
Engine container resources	The Engine block replaces the Preset or class block when the Engine sets requests, limits, or claims
Engine container environment and mounts	Firebolt Operator entries, then class entries, then Preset entries, then Engine entries; reserved names are rejected or omitted

The Firebolt Operator owns fields required for Engine identity, networking, probes, and StatefulSet behavior. See the FireboltEngineClass CRD reference for the complete allowed-field table.

Override a class image for one Engine

Use the class image as the shared default:

apiVersion: compute.firebolt.io/v1alpha1
kind: FireboltEngineClass
metadata:
  name: production
  namespace: firebolt
spec:
  template:
    spec:
      containers:
        - name: engine
          image: example.com/firebolt/engine:stable

Override it on one Engine:

apiVersion: compute.firebolt.io/v1alpha1
kind: FireboltEngine
metadata:
  name: canary
  namespace: firebolt
spec:
  instanceRef: production
  engineClassRef: production
  replicas: 1
  template:
    spec:
      containers:
        - name: engine
          image: example.com/firebolt/engine:candidate

Inherited Engine settings

Field	Resolution
storage	Whole setting. The Engine backend wins when set; otherwise Preset; otherwise the class; default is emptyDir.
customEngineConfig	Deep merge: Firebolt Operator configuration, class configuration, Preset configuration, then Engine configuration. Engine keys win. Protected identity, routing, and topology paths cannot be overridden.
rollout	Engine, class, then graceful. Preset does not carry this field.
drainCheckEnabled	Engine, class, then true. Preset does not carry this field.
drainCheckInterval	Engine, class, then Firebolt Operator default. Preset does not carry this field.
autoStop	Whole setting. The Engine policy replaces the class policy when set. Preset does not carry this field.
uiSidecar	Engine, class, then false. Preset does not carry this field.

FireboltEnginePreset

FireboltEnginePreset is an optional ambient overlay in the same namespace. Engines do not reference it by name. The object must be named firebolt — a validation rule baked into the CRD pins the name, so name uniqueness caps a namespace at one object.

Set spec.requirePreset: true on an Engine to keep it from becoming Ready until that object exists and is Ready. A present but unready Preset object fails closed for every Engine in the namespace even when requirePreset is unset.

See FireboltEnginePreset overview.

Class changes

Changes to class settings that alter Engine pods roll every bound Engine in the namespace. These include the pod template, storage, custom Engine configuration, and UI sidecar setting. A FireboltEnginePreset edit to the pod template, storage, or custom Engine configuration rolls every Engine in the namespace.

Changes to rollout, drain-check, and auto-stop policy take effect without forcing a pod rollout by themselves.

Inspect the number of referencing Engines with:

kubectl get firengc production -n firebolt

Delete a class

Class deletion remains blocked while Engines in the same namespace reference it. Remove or replace spec.engineClassRef on every bound Engine, wait for those updates to reconcile, then delete the class.

If deletion is blocked, status.conditions[type=Ready] reports reason DeletionBlocked and status.boundEngines shows the current consumer count.