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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>
158 lines
9.4 KiB
Markdown
158 lines
9.4 KiB
Markdown
# CSI RBD Plugin
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The RBD CSI plugin is able to provision new RBD images and
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attach and mount those to workloads.
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## Building
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CSI plugin can be compiled in a form of a binary file or in a form of a
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Docker image. When compiled as a binary file, the result is stored in
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`_output/` directory with the name `cephcsi`. When compiled as an image, it's
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stored in the local Docker image store with name `cephcsi`.
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Building binary:
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```bash
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make cephcsi
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```
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Building Docker image:
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```bash
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make image-cephcsi
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```
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## Configuration
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**Available command line arguments:**
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| Option | Default value | Description |
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| ------------------- | --------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `--endpoint` | `unix://tmp/csi.sock` | CSI endpoint, must be a UNIX socket |
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| `--drivername` | `rbd.csi.ceph.com` | Name of the driver (Kubernetes: `provisioner` field in StorageClass must correspond to this value) |
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| `--nodeid` | _empty_ | This node's ID |
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| `--type` | _empty_ | Driver type `[rbd | cephfs]` If the driver type is set to `rbd` it will act as a `rbd plugin` or if it's set to `cephfs` will act as a `cephfs plugin` |
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| `--containerized` | true | Whether running in containerized mode |
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| `--instanceid` | "default" | Unique ID distinguishing this instance of Ceph CSI among other instances, when sharing Ceph clusters across CSI instances for provisioning |
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| `--metadatastorage` | _empty_ | Points to where legacy (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) |
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| `--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. |
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**Available volume parameters:**
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| Parameter | Required | Description |
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| ----------------------------------------------------------------------------------------------------- | -------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
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| `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 |
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| `pool` | yes | Ceph pool into which the RBD image shall be created |
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| `imageFormat` | no | RBD image format. Defaults to `2`. See [man pages](http://docs.ceph.com/docs/mimic/man/8/rbd/#cmdoption-rbd-image-format) |
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| `imageFeatures` | no | RBD image features. Available for `imageFormat=2`. CSI RBD currently supports only `layering` feature. See [man pages](http://docs.ceph.com/docs/mimic/man/8/rbd/#cmdoption-rbd-image-feature) |
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| `csi.storage.k8s.io/provisioner-secret-name`, `csi.storage.k8s.io/node-publish-secret-name` | yes (for Kubernetes) | name of the Kubernetes Secret object containing Ceph client credentials. Both parameters should have the same value |
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| `csi.storage.k8s.io/provisioner-secret-namespace`, `csi.storage.k8s.io/node-publish-secret-namespace` | yes (for Kubernetes) | namespaces of the above Secret objects |
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| `mounter` | no | if set to `rbd-nbd`, use `rbd-nbd` on nodes that have `rbd-nbd` and `nbd` kernel modules to map rbd images |
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**NOTE:** An accompanying CSI configuration file, needs to be provided to the
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running pods. Refer to [Creating CSI configuration](../examples/README.md#creating-csi-configuration)
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for more information.
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**NOTE:** A suggested way to populate and retain uniqueness of the clusterID is
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to use the output of `ceph fsid` of the Ceph cluster to be used for
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provisioning.
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**Required secrets:**
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User credentials, with required access to the pool being used in the storage class,
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is required for provisioning new RBD images.
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## Deployment with Kubernetes
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Requires Kubernetes 1.13+
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if your cluster version is 1.13.x please use [rbd v1.13
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templates](../deploy/rbd/kubernetes/v1.13) or else use [rbd v1.14+
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templates](../deploy/rbd/kubernetes/v1.14+)
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Your Kubernetes cluster must allow privileged pods (i.e. `--allow-privileged`
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flag must be set to true for both the API server and the kubelet). Moreover, as
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stated in the [mount propagation
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docs](https://kubernetes.io/docs/concepts/storage/volumes/#mount-propagation),
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the Docker daemon of the cluster nodes must allow shared mounts.
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YAML manifests are located in `deploy/rbd/kubernetes`.
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**Deploy RBACs for sidecar containers and node plugins:**
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```bash
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kubectl create -f csi-provisioner-rbac.yaml
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kubectl create -f csi-nodeplugin-rbac.yaml
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```
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Those manifests deploy service accounts, cluster roles and cluster role
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bindings. These are shared for both RBD and CephFS CSI plugins, as they require
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the same permissions.
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**Deploy ConfigMap for CSI plugins:**
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```bash
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kubectl create -f csi-config-map.yaml
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```
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The config map deploys an empty CSI configuration that is mounted as a volume
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within the Ceph CSI plugin pods. To add a specific Ceph clusters configuration
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details, refer to [Creating CSI configuration for RBD based
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provisioning](../examples/README.md#creating-csi-configuration-for-rbd-based-provisioning)
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for more information.
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**Deploy CSI sidecar containers:**
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```bash
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kubectl create -f csi-rbdplugin-provisioner.yaml
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```
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Deploys stateful set of provision which includes external-provisioner
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,external-attacher,csi-snapshotter sidecar containers and CSI RBD plugin.
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**Deploy RBD CSI driver:**
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```bash
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kubectl create -f csi-rbdplugin.yaml
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```
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Deploys a daemon set with two containers: CSI node-driver-registrar and the CSI
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RBD driver.
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## Verifying the deployment in Kubernetes
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After successfully completing the steps above, you should see output similar to this:
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```bash
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$ kubectl get all
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NAME READY STATUS RESTARTS AGE
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pod/csi-rbdplugin-fptqr 2/2 Running 0 21s
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pod/csi-rbdplugin-provisioner-0 4/4 Running 0 22s
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NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
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service/csi-rbdplugin-provisioner ClusterIP 10.104.2.130 <none> 12345/TCP 23s
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...
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```
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Once the CSI plugin configuration is updated with details from a Ceph cluster of
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choice, you can try deploying a demo pod from examples/rbd using the
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instructions [provided](../examples/README.md#deploying-the-storage-class) to
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test the deployment further.
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## Deployment with Helm
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The same requirements from the Kubernetes section apply here, i.e. Kubernetes
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version, privileged flag and shared mounts.
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The Helm chart is located in `deploy/rbd/helm`.
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**Deploy Helm Chart:**
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```bash
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helm install ./deploy/rbd/helm
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```
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The Helm chart deploys all of the required resources to use the CSI RBD driver.
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After deploying the chart you can verify the deployment using the instructions
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above for verifying the deployment with Kubernetes
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