Standalone-cinder external provisioner
The standalone-cinder external provisioner fulfills persistent volume claims by creating cinder volumes and mapping them to natively supported volume sources. This approach allows cinder to be used as a storage service whether or not the cluster is deployed on Openstack. By mapping cinder volume connection information to native volume sources, persistent volumes can be attached and mounted using the standard kubelet machinery and without help from cinder.
Mapping cinder volumes to native PVs
The provisioner works by mapping cinder volume connections (iscsi, rbd, fc, etc) to the corresponding native/raw kubernetes volume types. New cinder types can be supported in the provisioner by creating a new implementation of the volunmeMapper interface. The implementation is responsible for building a PersistentVolumeSource from cinder connection information and for setup and teardown of any authentication (CHAP secret, cephx secret, etc) if required.
Support for cinder backends without a corresponding kubernetes raw volume implementation could be added in the future by providing a FlexVolume implementation for the type.
Connecting to cinder
The provisioner directly uses the gophercloud SDK to connect to cinder (as opposed to use of the cloudprovider interface). The intention is to support two modes of operation: a conventional cinder deployment with keystone managing authentication and providing the service catalog, and a standalone configuration where cinder is accessed directly.
Conventional cinder deployments can be used by supplying a clound config file identical to the one you would use to configure an openstack cloud provider.
Workflows
| User | Kubernetes | Provisioner | Cinder |
|---|---|---|---|
| Provision storage | |||
| Issue a PVC for a 100GB RWO volume | |||
| Posted the PVC on API server | |||
| Acquire the PVC and call cinder create | |||
| Create 100GB volume and return info | |||
| Call cinder reserve | |||
| Volume is marked as reserved/attaching | |||
| Call cinder os-initialize_connection | |||
| Create connection on storage server and return info (ISCSI target and LUN info) | |||
| Create PV using ISCSI as raw volume type using connection info | |||
| Bind the PV to the PVC | |||
| Use storage | |||
| Create a Pod including the PVC | |||
| Attach ISCSI PV to node | |||
| Create filesystem on device and mount into Pod | |||
| Pod is running | |||
| Delete Pod | |||
| Pod is stopped | |||
| Unmount filesystem | |||
| Detach ISCSI PV | |||
| Delete storage | |||
| Delete PVC | |||
| Call cinder os-terminate_connection | |||
| Remove connection on storage server | |||
| Call cinder unreserve | |||
| Volume is marked as available | |||
| Call cinder delete | |||
| Delete volume from storage | |||
| Delete PV |