ceph-csi/examples

How to test RBD and CephFS plugins with Kubernetes 1.14+

Deploying Ceph-CSI services

Create ceph-config configmap using the following command.

kubectl apply -f ./ceph-conf.yaml

Both rbd and cephfs directories contain plugin-deploy.sh and plugin-teardown.sh helper scripts. You can use those to help you deploy/teardown RBACs, sidecar containers and the plugin in one go. By default, they look for the YAML manifests in ../../deploy/{rbd,cephfs}/kubernetes. You can override this path by running

./plugin-deploy.sh /path/to/my/manifests

Creating CSI configuration

The CSI plugin requires configuration information regarding the Ceph cluster(s), that would host the dynamically or statically provisioned volumes. This is provided by adding a per-cluster identifier (referred to as clusterID), and the required monitor details for the same, as in the provided sample config map.

Gather the following information from the Ceph cluster(s) of choice,

• Ceph monitor list
  • Typically in the output of ceph mon dump
  • Used to prepare a list of monitors in the CSI configuration file
• Ceph Cluster fsid
  • If choosing to use the Ceph cluster fsid as the unique value of clusterID,
    • Output of ceph fsid
  • Alternatively, choose a <cluster-id> value that is distinct per Ceph cluster in use by this kubernetes cluster

Update the sample configmap with values from a Ceph cluster and replace <cluster-id> with the chosen clusterID, to create the manifest for the configmap which can be updated in the cluster using the following command,

kubectl replace -f ./csi-config-map-sample.yaml

Storage class and snapshot class, using <cluster-id> as the value for the option clusterID, can now be created on the cluster.

Running CephCSI with pod networking

The current problem with Pod Networking, is when a CephFS/RBD volume is mounted in a pod using Ceph CSI and then the CSI CephFS/RBD plugin is restarted or terminated (e.g. by restarting or deleting its DaemonSet), all operations on the volume become blocked, even after restarting the CSI pods.

The only workaround is to restart the node where the Ceph CSI plugin pod was restarted. This can be mitigated by running the rbd map/mount -t commands in a different network namespace which does not get deleted when the CSI CephFS/RBD plugin is restarted or terminated.

If someone wants to run the CephCSI with the pod networking they can still do by setting the netNamespaceFilePath. If this path is set CephCSI will execute the rbd map/mount -t commands after entering the network namespace specified by netNamespaceFilePath with the nsenter command.

netNamespaceFilePath should point to the network namespace of some long-running process, typically it would be a symlink to /proc/<long running process id>/ns/net.

The long-running process can also be another pod which is a Daemonset which never restarts. This Pod should only be stopped and restarted when a node is stopped so that volume operations do not become blocked. The new DaemonSet pod can contain a single container, responsible for holding its pod network alive. It is used as a passthrough by the CephCSI plugin pod which when mounting or mapping will use the network namespace of this pod.

Once the pod is created get its PID and create a symlink to /proc/<PID>/ns/net in the hostPath volume shared with the csi-plugin pod and specify the path in the netNamespaceFilePath option.

Note This Pod should have hostPID: true in the Pod Spec.

Deploying the storage class

Once the plugin is successfully deployed, you'll need to customize storageclass.yaml and secret.yaml manifests to reflect your Ceph cluster setup. Please consult the documentation for info about available parameters.

After configuring the secrets, monitors, etc. you can deploy a testing Pod mounting a RBD image / CephFS volume:

kubectl create -f secret.yaml
kubectl create -f storageclass.yaml
kubectl create -f pvc.yaml
kubectl create -f pod.yaml

Other helper scripts:

• logs.sh output of the plugin
• exec-bash.sh logs into the plugin's container and runs bash

How to test RBD Snapshot feature

Before continuing, make sure you enabled the required feature gate VolumeSnapshotDataSource=true in your Kubernetes cluster.

In the examples/rbd directory you will find two files related to snapshots: snapshotclass.yaml and snapshot.yaml.

Once you created your RBD volume, you'll need to customize at least snapshotclass.yaml and make sure the clusterid parameter matches your Ceph cluster setup. If you followed the documentation to create the rbdplugin, you shouldn't have to edit any other file.

Note that it is recommended to create a volume snapshot or a PVC clone only when the PVC is not in use.

After configuring everything you needed, deploy the snapshot class:

kubectl create -f snapshotclass.yaml

Verify that the snapshot class was created:

$ kubectl get volumesnapshotclass
NAME                      AGE
csi-rbdplugin-snapclass   4s

Create a snapshot from the existing PVC:

kubectl create -f snapshot.yaml

To verify if your volume snapshot has successfully been created, run the following:

$ kubectl get volumesnapshot
NAME               AGE
rbd-pvc-snapshot   6s

To check the status of the snapshot, run the following:

$ kubectl describe volumesnapshot rbd-pvc-snapshot
Name:         rbd-pvc-snapshot
Namespace:    default
Labels:       <none>
Annotations:  <none>
API Version:  snapshot.storage.k8s.io/v1alpha1
Kind:         VolumeSnapshot
Metadata:
  Creation Timestamp:  2019-02-06T08:52:34Z
  Finalizers:
    snapshot.storage.kubernetes.io/volumesnapshot-protection
  Generation:        5
  Resource Version:  84239
  Self Link:         /apis/snapshot.storage.k8s.io/v1alpha1/namespaces/default/volumesnapshots/rbd-pvc-snapshot
  UID:               8b9b5740-29ec-11e9-8e0f-b8ca3aad030b
Spec:
  Snapshot Class Name:    csi-rbdplugin-snapclass
  Snapshot Content Name:  snapcontent-8b9b5740-29ec-11e9-8e0f-b8ca3aad030b
  Source:
    API Group:  <nil>
    Kind:       PersistentVolumeClaim
    Name:       rbd-pvc
Status:
  Creation Time:  2019-02-06T08:52:34Z
  Ready To Use:   true
  Restore Size:   1Gi
Events:           <none>

To be sure everything is OK you can run rbd snap ls [your-pvc-name] inside one of your Ceph pod.

To restore the snapshot to a new PVC, deploy pvc-restore.yaml and a testing pod pod-restore.yaml:

kubectl create -f pvc-restore.yaml
kubectl create -f pod-restore.yaml

How to test RBD MULTI_NODE_MULTI_WRITER BLOCK feature

Requires feature-gates: BlockVolume=true CSIBlockVolume=true

NOTE The MULTI_NODE_MULTI_WRITER capability is only available for Volumes that are of access_type block

WARNING This feature is strictly for workloads that know how to deal with concurrent access to the Volume (eg Active/Passive applications). Using RWX modes on non clustered file systems with applications trying to simultaneously access the Volume will likely result in data corruption!

Following are examples for issuing a request for a Block ReadWriteMany Claim, and using the resultant Claim for a POD

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: block-pvc
spec:
  accessModes:
  - ReadWriteMany
  volumeMode: Block
  resources:
    requests:
      storage: 1Gi
  storageClassName: csi-rbd-sc

Create a POD that uses this PVC:

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
    - name: my-container
      image: docker.io/library/debian:latest
      command: ["/bin/bash", "-c"]
      args: [ "tail -f /dev/null" ]
      volumeDevices:
        - devicePath: /dev/rbdblock
          name: my-volume
      imagePullPolicy: IfNotPresent
  volumes:
    - name: my-volume
      persistentVolumeClaim:
        claimName: block-pvc

Now, we can create a second POD (ensure the POD is scheduled on a different node; multiwriter single node works without this feature) that also uses this PVC at the same time, again wait for the pod to enter running state, and verify the block device is available.

apiVersion: v1
kind: Pod
metadata:
  name: another-pod
spec:
  containers:
    - name: my-container
      image: docker.io/library/debian:latest
      command: ["/bin/bash", "-c"]
      args: [ "tail -f /dev/null" ]
      volumeDevices:
        - devicePath: /dev/rbdblock
          name: my-volume
      imagePullPolicy: IfNotPresent
  volumes:
    - name: my-volume
      persistentVolumeClaim:
        claimName: block-pvc

Wait for the PODs to enter Running state, check that our block device is available in the container at /dev/rdbblock in both containers:

$ kubectl exec -it my-pod -- fdisk -l /dev/rbdblock
Disk /dev/rbdblock: 1 GiB, 1073741824 bytes, 2097152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 4194304 bytes / 4194304 bytes

$ kubectl exec -it another-pod -- fdisk -l /dev/rbdblock
Disk /dev/rbdblock: 1 GiB, 1073741824 bytes, 2097152 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 4194304 bytes / 4194304 bytes