Skip Kubernetes Attach and Detach
|Status||Min K8s Version||Max K8s Version||cluster-driver-registrar Version|
Volume drivers, like NFS, for example, have no concept of an attach (
ControllerPublishVolume). However, Kubernetes always executes
Detach operations even if the CSI driver does not implement an attach operation (i.e. even if the CSI Driver does not implement a
This was problematic because it meant all CSI drivers had to handle Kubernetes attachment. CSI Drivers that did not implement the
PUBLISH_UNPUBLISH_VOLUME controller capability could work around this by deploying an external-attacher and the
external-attacher would responds to Kubernetes attach operations and simply do a noop (because the CSI driver did not advertise the
PUBLISH_UNPUBLISH_VOLUME controller capability).
Although the workaround works, it adds an unnecessary operation (round-trip) in the preparation of a volume for a container, and requires CSI Drivers to deploy an unnecessary sidecar container (
Skip Attach with CSI Driver Object
The CSIDriver Object enables CSI Drivers to specify how Kubernetes should interact with it.
attachRequired field instructs Kubernetes to skip any attach operation altogether.
For example, the existence of the following object would cause Kubernetes to skip attach operations for all CSI Driver
apiVersion: storage.k8s.io/v1beta1 kind: CSIDriver metadata: name: testcsidriver.example.com spec: attachRequired: false
CSIDriver object should be manually included in the driver deployment manifests.
Previously, the cluster-driver-registrar sidecar container could be deployed to automatically create the object. Once the flags to this container are configured correctly, it will automatically create a CSIDriver Object when it starts with the correct fields set.
In alpha, this feature was enabled via the CSIDriver Object CRD.
apiVersion: csi.storage.k8s.io/v1alpha1 kind: CSIDriver metadata: ....