CSI external-provisioner

Status and Releases

Git Repository: https://github.com/kubernetes-csi/external-provisioner

Status: GA/Stable

Supported Versions

Unsupported Versions

Description

The CSI external-provisioner is a sidecar container that watches the Kubernetes API server for PersistentVolumeClaim objects.

It calls CreateVolume against the specified CSI endpoint to provision a new volume.

Volume provisioning is triggered by the creation of a new Kubernetes PersistentVolumeClaim object, if the PVC references a Kubernetes StorageClass, and the name in the provisioner field of the storage class matches the name returned by the specified CSI endpoint in the GetPluginInfo call.

Once a new volume is successfully provisioned, the sidecar container creates a Kubernetes PersistentVolume object to represent the volume.

The deletion of a PersistentVolumeClaim object bound to a PersistentVolume corresponding to this driver with a delete reclaim policy causes the sidecar container to trigger a DeleteVolume operation against the specified CSI endpoint to delete the volume. Once the volume is successfully deleted, the sidecar container also deletes the PersistentVolume object representing the volume.

DataSources

The external-provisioner provides the ability to request a volume be pre-populated from a data source during provisioning. For more information on how data sources are handled see DataSources.

Snapshot

The CSI external-provisioner supports the Snapshot DataSource. If a Snapshot CRD is specified as a data source on a PVC object, the sidecar container fetches the information about the snapshot by fetching the SnapshotContent object and populates the data source field in the resulting CreateVolume call to indicate to the storage system that the new volume should be populated using the specified snapshot.

PersistentVolumeClaim (clone)

Cloning is also implemented by specifying a kind: of type PersistentVolumeClaim in the DataSource field of a Provision request. It's the responsbility of the external-provisioner to verify that the claim specified in the DataSource object exists, is in the same storage class as the volume being provisioned and that the claim is currently Bound.

StorageClass Parameters

When provisioning a new volume, the CSI external-provisioner sets the map<string, string> parameters field in the CSI CreateVolumeRequest call to the key/values specified in the StorageClass it is handling.

The CSI external-provisioner (v1.0.1+) also reserves the parameter keys prefixed with csi.storage.k8s.io/. Any StorageClass keys prefixed with csi.storage.k8s.io/ are not passed to the CSI driver as an opaque parameter.

The following reserved StorageClass parameter keys trigger behavior in the CSI external-provisioner:

• csi.storage.k8s.io/provisioner-secret-name
• csi.storage.k8s.io/provisioner-secret-namespace
• csi.storage.k8s.io/controller-publish-secret-name
• csi.storage.k8s.io/controller-publish-secret-namespace
• csi.storage.k8s.io/node-stage-secret-name
• csi.storage.k8s.io/node-stage-secret-namespace
• csi.storage.k8s.io/node-publish-secret-name
• csi.storage.k8s.io/node-publish-secret-namespace
• csi.storage.k8s.io/fstype

If the PVC VolumeMode is set to Filesystem, and the value of csi.storage.k8s.io/fstype is specified, it is used to populate the FsType in CreateVolumeRequest.VolumeCapabilities[x].AccessType and the AccessType is set to Mount.

For more information on how secrets are handled see Secrets & Credentials.

Example StorageClass:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: gold-example-storage
provisioner: exampledriver.example.com
parameters:
  disk-type: ssd
  csi.storage.k8s.io/fstype: ext4
  csi.storage.k8s.io/provisioner-secret-name: mysecret
  csi.storage.k8s.io/provisioner-secret-namespace: mynamespace

PersistentVolumeClaim and PersistentVolume Parameters

The CSI external-provisioner (v1.6.0+) introduces the --extra-create-metadata flag, which automatically sets the following map<string, string> parameters in the CSI CreateVolumeRequest:

• csi.storage.k8s.io/pvc/name
• csi.storage.k8s.io/pvc/namespace
• csi.storage.k8s.io/pv/name

These parameters are not part of the StorageClass, but are internally generated using the name and namespace of the source PersistentVolumeClaim and PersistentVolume.

Usage

CSI drivers that support dynamic volume provisioning should use this sidecar container, and advertise the CSI CREATE_DELETE_VOLUME controller capability.

For detailed information (binary parameters, RBAC rules, etc.), see https://github.com/kubernetes-csi/external-provisioner/blob/master/README.md.

Deployment

The CSI external-provisioner is deployed as a controller. See deployment section for more details.