sequence-cache.wsd

@startuml "pmem-csi-cache-sequence-diagram"

title \nDynamic provisioning of pmem-csi "cache" volume\n

skinparam BoxPadding 40

actor Admin as admin #red
actor User as user
entity Kubernetes as k8s
box "Master node"
entity kubelet as masterkubelet
participant "external-provisioner" as provisioner
participant "external-attacher" as attacher
participant "pmem-csi-driver" as masterdriver
endbox

box "Compute node X"
entity kubelet as nodekubeletX
participant "pmem-csi-driver" as nodedriverX
endbox

box "Compute node Y"
entity kubelet as nodekubeletY
participant "pmem-csi-driver" as nodedriverY
endbox

== Driver setup ==
admin->k8s:Label nvdimm nodes: <b>storage=nvdimm</b>
k8s->admin

' deploy driver
admin->k8s:deploy driver\nkubectl create -f pmem-csi.yaml
k8s->admin
k8s->masterkubelet:start driver pod
masterkubelet-->provisioner:start container
masterkubelet-->attacher:start container
masterkubelet-->masterdriver:start container
note right of masterdriver
    listen on tcp port 10000
end note
k8s-->nodekubeletX:start driver pod
nodekubeletX-->nodedriverX:start container
note left of nodedriverX
    * prepare logical volume groups
    * listen on port 10001
    * listen on unix socket:
      /var/lib/kubelet/plugins/pmem-csi/csi.sock
end note
nodedriverX->masterdriver:RegistryServer.RegisterNodeController(\n{nodeId:"node-x", endpoint:"http://ip:10001"})

k8s-->nodekubeletY:start driver pod
nodekubeletY-->nodedriverY:start container
note left of nodedriverY
    * prepare logical volume groups
    * listen on port 10001
    * listen on unix socket:
      /var/lib/kubelet/plugins/pmem-csi/csi.sock
end note
nodedriverY->masterdriver:RegistryServer.RegisterNodeController(\n{nodeId:"node-y", endpoint:"http://ip:10001"})

' install a storage class
admin->k8s:create StorageClass\nkubectl create -f pmem-storageclass-cache.yaml
note left of k8s
  metadata:
    name: pmem-csi-sc-cache
  volumeBindingMode: <b>Immediate
  paramters:
    persistencyModel: cache
    cacheSize: "2"
end note
k8s->admin

' provision a cache volume
== Volume provisioning ==
admin->k8s:create PVC object\nkubectl create -f pmem-pvc-cache.yaml
note left of k8s
  metatdata:
    name: pmem-csi-pvc-cache
  spec:
    storageClassName: pmem-csi-sc-cache
end note
k8s->admin
k8s-->provisioner:<<Event>>\nPersistentVolumeClaim created
activate provisioner
provisioner->masterdriver:CSI.Controller.CreateVolume()
masterdriver->nodedriverX:csi.Controller.CreateVolume()
nodedriverX->nodedriverX:create pmem volume
nodedriverX->masterdriver:success
masterdriver->nodedriverY:csi.Controller.CreateVolume()
nodedriverY->nodedriverY:create pmem volume
nodedriverY->masterdriver:success
masterdriver->provisioner:success
note left of masterdriver
  prepare Topology information:
  Volume{
    accessible_topology: [
      segments:{ "pmem-csi.intel.com/node":"node-x"},
      segments:{ "pmem-csi.intel.com/node":"node-y"} ]
  }
end note
provisioner->k8s:Create PV object
deactivate provisioner

== Volume usage ==
' Start an application
user->k8s:Create application pod
note left of k8s
  volumes:
  - name: my-csi-volume
    persistentVolumeClaim:
      claimName: pmem-csi-pvc-cache
end note

k8s->user:success

k8s->nodekubeletX:schedules pod on node-x
note right of k8s
  Kubernetes is might choose <b>node-x</b> or <b>node-y</b>.
end note

k8s-->nodekubeletX:make available volume to pod
nodekubeletX->nodedriverX:csi.Node.StageVolume()
activate nodedriverX
nodedriverX->nodedriverX:mount pmem device
nodedriverX->nodekubeletX:success
deactivate nodedriverX

nodekubeletX->nodedriverX:csi.Node.PublishVolume()
activate nodedriverX
nodedriverX->nodedriverX:bind mount pmem device
nodedriverX->nodekubeletX:success
deactivate nodedriverX

' deprovision a cache volume
== Volume Deletion ==
' stop pod
user->k8s:stop applicaiton pod
k8s->user:success
k8s->nodekubeletX:stop pod containers

nodekubeletX->nodedriverX:csi.Node.UnPublishVolume()
activate nodedriverX
nodedriverX->nodedriverX:unmout pod's bind mount
nodedriverX->nodekubeletX:success
deactivate nodedriverX

nodekubeletX->nodedriverX:csi.Node.UnstageVolume()
activate nodedriverX
nodedriverX->nodedriverX:unmount pmem device
nodedriverX->nodekubeletX:success
deactivate nodedriverX

'''''''''''''''''''''''''''
admin->k8s:Delete PVC object\nkubectl delete pvc pmem-pvc-cache
k8s->admin
k8s-->provisioner:<<Event>>\nPersistentVolumeClaim deleted
activate provisioner
provisioner->masterdriver:CSI.Controller.DeleteVolume()
masterdriver->nodedriverX:csi.Controller.DeleteVolume()
nodedriverX->nodedriverX:delete pmem volume
nodedriverX->masterdriver:success
masterdriver->nodedriverY:csi.Controller.DeleteVolume()
nodedriverY->nodedriverY:delete pmem volume
nodedriverY->masterdriver:success
masterdriver->provisioner:success
provisioner->k8s:Delete PV object
deactivate provisioner


@enduml