Mount CSI Ephemeral Volumes

Some Kubernetes drivers publish a resource to a pod through a CSI ephemeral inline volume rather than through a PersistentVolumeClaim. The SPIFFE CSI driver is the common example: it mounts the SPIRE Agent's Workload API socket into the pod so the workload can obtain its identity document (SVID).

A PVC cannot carry that kind of volume:

• Dynamic provisioning goes through the CSI Controller Service (CreateVolume). Drivers like csi.spiffe.io implement only the Node Service and declare volumeLifecycleModes: [Ephemeral], so a PVC against them stays Pending forever.
• A bound PersistentVolume carries node affinity, which would stop the pod from ever being rescheduled to another node. The socket, however, is node-local and exists on every node.
• A PVC is meant to outlive its pod. This kind of volume must disappear with the pod.

The operator therefore accepts a csi volume source alongside emptyDir and hostPath.

Prerequisite: the CSI driver must already be installed in the cluster. The operator only references it by name; it does not install anything.

1. By PhoenixAICluster CRD

Set csi on an entry of storageVolumes. The csi field takes a Kubernetes CSIVolumeSource.

apiVersion: phoenixdata.ai/v1
kind: PhoenixAICluster
metadata:
  name: phoenixaicluster-sample
spec:
  phoenixAIFeSpec:
    replicas: 3
    image: starrocks/fe-ubuntu:latest
    storageVolumes:
      - name: spiffe-workload-api
        storageClassName: csi
        mountPath: /spiffe-workload-api
        readOnly: true
        csi:
          driver: csi.spiffe.io
          readOnly: true

storageClassName: csi may be omitted — setting the csi field alone is enough. Spelling it out makes the intent obvious next to neighbouring PVC-backed volumes.

Supported on phoenixAIFeSpec, phoenixAICnSpec, and phoenixAIFeProxySpec.

The operator rejects configurations that would otherwise be silently ignored:

Configuration	Error
storageClassName: csi without a csi block, or with an empty csi.driver	csi is required if storageClassName is csi, and csi.driver must not be empty
csi together with hostPath on the same volume	csi and hostPath can not be set at the same time
csi together with any other storageClassName (gp3, emptyDir, ...)	if csi is set, storageClassName must be empty or "csi"

2. By Helm chart

Each component has a csiVolumes list, next to emptyDirs and hostPaths:

phoenixAIFeSpec:
  csiVolumes:
    - name: spiffe-workload-api
      mountPath: /spiffe-workload-api
      readOnly: true
      csi:
        driver: csi.spiffe.io
        readOnly: true

When using the parent kube-anywhere chart, nest this under the phoenixai: key.

3. Example: mounting the SPIFFE workload API socket

Install the SPIFFE CSI driver first, following the SPIRE documentation. Confirm it registered:

kubectl get csidriver csi.spiffe.io

Then deploy the cluster:

helm install kube-anywhere phoenixai/kube-anywhere -f values.yaml

with values.yaml:

phoenixai:
  phoenixAIFeSpec:
    csiVolumes:
      - name: spiffe-workload-api
        mountPath: /spiffe-workload-api
        readOnly: true
        csi:
          driver: csi.spiffe.io
          readOnly: true

Verify the socket reached the pod:

kubectl exec phoenixaicluster-sample-fe-0 -- ls -l /spiffe-workload-api

Expected: a spire-agent.sock entry.