ceph-csi/docs/deploy-cephfs.md
Niels de Vos 31648c8feb provisioners: add reconfiguring of PID limit
The container runtime CRI-O limits the number of PIDs to 1024 by
default. When many PVCs are requested at the same time, it is possible
for the provisioner to start too many threads (or go routines) and
executing 'rbd' commands can start to fail. In case a go routine can not
get started, the process panics.

The PID limit can be changed by passing an argument to kubelet, but this
will affect all pids running on a host. Changing the parameters to
kubelet is also not a very elegant solution.

Instead, the provisioner pod can change the configuration itself. The
pod is running in privileged mode and can write to /sys/fs/cgroup where
the limit is configured.

With this change, the limit is configured to 'max', just as if there is
no limit at all. The logs of the csi-rbdplugin in the provisioner pod
will reflect the change it makes when starting the service:

    $ oc -n rook-ceph logs -c csi-rbdplugin csi-rbdplugin-provisioner-0
    ..
    I0726 13:59:19.737678       1 cephcsi.go:127] Initial PID limit is set to 1024
    I0726 13:59:19.737746       1 cephcsi.go:136] Reconfigured PID limit to -1 (max)
    ..

It is possible to pass a different limit on the commandline of the
cephcsi executable. The following flag has been added:

    --pidlimit=<int>       the PID limit to configure through cgroups

This accepts special values -1 (max) and 0 (default, do not
reconfigure). Other integers will be the limit that gets configured in
cgroups.

Signed-off-by: Niels de Vos <ndevos@redhat.com>
2019-08-13 14:43:29 +00:00

12 KiB

CSI CephFS plugin

The CSI CephFS plugin is able to both provision new CephFS volumes and attach and mount existing ones to workloads.

Building

CSI plugin can be compiled in the form of a binary file or in the form of a Docker image. When compiled as a binary file, the result is stored in _output/ directory with the name cephcsi. When compiled as an image, it's stored in the local Docker image store with name cephcsi.

Building binary:

make cephcsi

Building Docker image:

make image-cephcsi

Configuration

NOTE: To make CephFS CSI driver version >= 1.1.0 work with Ceph v14.2.2 cluster (not deployed by rook), you need to add the following settings in the mgr section of the ceph.conf used by the Ceph manager daemon, and restart the Ceph manager daemon.

[mgr]
client mount uid = 0
client mount gid = 0

This is due to an issue in Ceph v14.2.2 that should be resolved in v14.2.3.

Available command line arguments:

Option Default value Description
--endpoint unix://tmp/csi.sock CSI endpoint, must be a UNIX socket
--drivername cephfs.csi.ceph.com Name of the driver (Kubernetes: provisioner field in StorageClass must correspond to this value)
--nodeid empty This node's ID
--type empty Driver type `[rbd
--volumemounter empty Default volume mounter. Available options are kernel and fuse. This is the mount method used if volume parameters don't specify otherwise. If left unspecified, the driver will first probe for ceph-fuse in system's path and will choose Ceph kernel client if probing failed.
--mountcachedir empty Volume mount cache info save dir. If left unspecified, the dirver will not record mount info, or it will save mount info and when driver restart it will remount volume it cached.
--instanceid "default" Unique ID distinguishing this instance of Ceph CSI among other instances, when sharing Ceph clusters across CSI instances for provisioning
--pluginpath "/var/lib/kubelet/plugins/" The location of cephcsi plugin on host
--metadatastorage empty Points to where older (1.0.0 or older plugin versions) metadata about provisioned volumes are kept, as file or in as k8s configmap (node or k8s_configmap respectively)
--pidlimit 0 Configure the PID limit in cgroups. The container runtime can restrict the number of processes/tasks which can cause problems while provisioning (or deleting) a large number of volumes. A value of -1 configures the limit to the maximum, 0 does not configure limits at all.

Available environmental variables:

KUBERNETES_CONFIG_PATH: if you use k8s_configmap as metadata store, specify the path of your k8s config file (if not specified, the plugin will assume you're running it inside a k8s cluster and find the config itself).

POD_NAMESPACE: if you use k8s_configmap as metadata store, POD_NAMESPACE is used to define in which namespace you want the configmaps to be stored

Available volume parameters:

Parameter Required Description
clusterID yes String representing a Ceph cluster, must be unique across all Ceph clusters in use for provisioning, cannot be greater than 36 bytes in length, and should remain immutable for the lifetime of the Ceph cluster in use
fsName yes CephFS filesystem name into which the volume shall be created
mounter no Mount method to be used for this volume. Available options are kernel for Ceph kernel client and fuse for Ceph FUSE driver. Defaults to "default mounter", see command line arguments.
pool no Ceph pool into which volume data shall be stored
csi.storage.k8s.io/provisioner-secret-name, csi.storage.k8s.io/node-stage-secret-name for Kubernetes Name of the Kubernetes Secret object containing Ceph client credentials. Both parameters should have the same value
csi.storage.k8s.io/provisioner-secret-namespace, csi.storage.k8s.io/node-stage-secret-namespace for Kubernetes Namespaces of the above Secret objects

NOTE: An accompanying CSI configuration file, needs to be provided to the running pods. Refer to Creating CSI configuration for more information.

NOTE: A suggested way to populate and retain uniqueness of the clusterID is to use the output of ceph fsid of the Ceph cluster to be used for provisioning.

Required secrets for provisioning: Admin credentials are required for provisioning new volumes

  • adminID: ID of an admin client
  • adminKey: key of the admin client

Required secrets for statically provisioned volumes: User credentials with access to an existing volume

  • userID: ID of a user client
  • userKey: key of a user client

Notes on volume size: when provisioning a new volume, max_bytes quota attribute for this volume will be set to the requested volume size (see Ceph quota documentation). A request for a zero-sized volume means no quota attribute will be set.

Deployment with Kubernetes

Requires Kubernetes 1.13+

if your cluster version is 1.13.x please use cephfs v1.13 templates or else use cephfs v1.14+ templates

Your Kubernetes cluster must allow privileged pods (i.e. --allow-privileged flag must be set to true for both the API server and the kubelet). Moreover, as stated in the mount propagation docs, the Docker daemon of the cluster nodes must allow shared mounts.

YAML manifests are located in deploy/cephfs/kubernetes.

Deploy RBACs for sidecar containers and node plugins:

kubectl create -f csi-provisioner-rbac.yaml
kubectl create -f csi-nodeplugin-rbac.yaml

Those manifests deploy service accounts, cluster roles and cluster role bindings. These are shared for both RBD and CephFS CSI plugins, as they require the same permissions.

Deploy ConfigMap for CSI plugins:

kubectl create -f csi-config-map.yaml

The configmap deploys an empty CSI configuration that is mounted as a volume within the Ceph CSI plugin pods. To add a specific Ceph clusters configuration details, refer to Creating CSI configuration for more information.

Deploy CSI sidecar containers:

kubectl create -f csi-cephfsplugin-provisioner.yaml

Deploys stateful set of provision which includes external-provisioner ,external-attacher for CSI CephFS.

Deploy CSI CephFS driver:

kubectl create -f csi-cephfsplugin.yaml

Deploys a daemon set with two containers: CSI node-driver-registrar and the CSI CephFS driver.

Verifying the deployment in Kubernetes

After successfully completing the steps above, you should see output similar to this:

$ kubectl get all
NAME                                 READY     STATUS    RESTARTS   AGE
pod/csi-cephfsplugin-provisioner-0   3/3       Running   0          25s
pod/csi-cephfsplugin-rljcv           2/2       Running   0          24s

NAME                                   TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)     AGE
service/csi-cephfsplugin-provisioner   ClusterIP   10.101.78.75     <none>        12345/TCP   26s
...

Once the CSI plugin configuration is updated with details from a Ceph cluster of choice, you can try deploying a demo pod from examples/cephfs using the instructions provided to test the deployment further.

Notes on volume deletion

Dynamically povisioned volumes are deleted by the driver, when requested to do so. Statically provisioned volumes, from plugin versions less than or equal to 1.0.0, are a no-op when a delete operation is performed against the same, and are expected to be deleted on the Ceph cluster by the user.