CSINodeInfo is an API object representing CSI Information at the Node level. CSINodeInfo contains a Spec and a Status, each containing Drivers represent the driver spec and status respectively. The CSIDriverInfoSpec represents the specification of the driver and is generally not changed, whereas the CSIDriverInfoStatus represents the current status of the driver and can be updated and reacted to by various components.
CSINodeInfo is created by Kubelet when the first CSI Driver is installed to the cluster and it is registered through the Kubelet device registration mechanism.
The CSIDriverInfoSpec for a driver is created upon installation of the CSI Driver to the cluster and it is registered through the Kubelet device registration mechanism. The spec is populated with information about the driver through the nodeinfomanager (inside Kubelet) and will remain unchanged from then on.
The CSIDriverInfoStatus for the driver is created upon installation of the CSI Driver to the cluster (the same time as the spec) and it is registered through the Kubelet device registration mechanism. The Status contains information about installation and the required Volume Plugin Mechanism of the driver. When the driver is installed/uninstalled through the Kubelet device registration mechanism the Available flag is flipped from true/false respectively. The migration status will also be updated when the flags for migration are set to true/false on the Kubelet for that Driver on that node.
Currently the only consumer of CSINodeInfo/CSIDriverInfo is the csi-external-provisioner. In the future, the Attach Detach Controller (ADC) will need to read this object to determine migration status on a per driver per node basis. The creation of the CSINodeInfo object could possibly race with the Attach/Detach controller as for CSI Migration the controller depend on the existence of the API object for the driver but it will not have been created yet. The ADC is expected to fail (and retry with exponential backoff) the operation if it is expecting the object and it has not yet been created.
For CSI Migration Alpha we expect any user who turns on the feature has both Kubelet and ADC at a version where the CSINodeInfo‘s are being created on Kubelet startup. We will not promote the feature to Beta (on by default) until the CSINodeInfo’s are being created on Kubelet startup for a 2 version skew to prevent the case where the CSINodeInfo does not exist when the ADC depends on it. This prevents the race described above becoming a permanent bad state.