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chore(doc): add manual steps to expand NFS volumes (#103)
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This PR adds manual steps that describes detailed steps
to expand NFS volume


Signed-off-by: mittachaitu <[email protected]>
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sai chaithanya authored Sep 15, 2021
1 parent 23d4176 commit ebd70a3
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61 changes: 61 additions & 0 deletions docs/tutorial/get-nfs-volume-details.sh
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#! /bin/bash

# Copyright 2021 The OpenEBS Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
# This script runs tests and generates a report file.

if [ $# -ne 2 ]; then
echo "Please specify NFS PVC name and namespace"
echo "$0 <nfs_pvc_name> <nfs_pvc_namespace>"
exit 1
fi
nfs_pvc_name=$1
nfs_pvc_namespace=$2
backend_pvc_name=""
backend_pvc_namespace=""

nfs_pv_name=$(kubectl get pvc "${nfs_pvc_name}" -n "${nfs_pvc_namespace}" -o jsonpath='{.spec.volumeName}')
if [ -z "$nfs_pv_name" ]; then
echo "Unable to find NFS PV for PVC ${nfs_pvc_namespace}/${nfs_pvc_name}"
exit 1
fi

all_pvc_namespaces=$(kubectl get pvc --all-namespaces -o jsonpath="{range .items[*]}{@.metadata.name};{@.metadata.namespace}:{end}")

for pvc_name_namespace in `echo $all_pvc_namespaces | tr ":" " "`; do
arr=(${pvc_name_namespace//;/ })
pvc_name=${arr[0]}
pvc_namespace=${arr[1]}
if [ "nfs-${nfs_pv_name}" == "${pvc_name}" ]; then
backend_pvc_name="$pvc_name"
backend_pvc_namespace="$pvc_namespace"
break
fi
done

if [ -z "$backend_pvc_name" ] || [ -z "$backend_pvc_namespace" ]; then
echo "Looks like ${nfs_pvc_namespace}/${nfs_pvc_name} is not a NFS PVC... Not able to find backend PVC"
exit 1
fi

backend_pv_name=$(kubectl get pvc "${backend_pvc_name}" -n "${backend_pvc_namespace}" -o jsonpath='{.spec.volumeName}')
echo ""
echo ""
echo "----------------------------------------------------------------"
echo "Backend PVC Name: ${backend_pvc_name}"
echo "Backend PVC Namespace: ${backend_pvc_namespace}"
echo "Backend PV Name: ${backend_pv_name}"
echo "NFS PV Name: ${nfs_pv_name}"
echo "NFS PVC Namespace/Name: ${nfs_pvc_namespace}/${nfs_pvc_name}"
170 changes: 170 additions & 0 deletions docs/tutorial/nfs-volume-resize.md
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# How to Expand/Resize NFS Volume

OpenEBS dynamic-nfs-provisioner **doesn't support** natively expanding NFS volume but we can accomplish the same operation by following a workaround.


For expanding NFS volume, you must ensure the following items(prerequisites) are taken care of:

- The BackendStorageClass must support volume expansion, which can configure by editing the StorageClass definition to have `allowVolumeExpansion: true`

```
kubectl patch sc openebs-lvmpv -p '{"allowVolumeExpansion": true}'
```

```sh
storageclass.storage.k8s.io/openebs-lvmpv patched
```
- NFS StorageClass must support volume expansion, which can configure by editing the NFS StorageClass defination to have `allowVolumeExpansion: true`

```
kubectl patch sc openebs-rwx -p '{"allowVolumeExpansion": true}'
```

```sh
storageclass.storage.k8s.io/openebs-rwx patched
```

## Steps to perform NFS Volume Expansion

- After meeting the prerequisites, Resize NFS volume by editing backend PVC `spec.resources.requests.storage` to reflect the newly desired size, which must be greater than the original size.
```sh
kubectl patch pvc <backend-pvc-name> -n <openebs-namespace> -p '{"spec": {"resources": {"requests": {"storage": "10Gi"}}}}'
```
**Note**: OpenEBS dynamic-nfs-provisioner will create backend PVC to provide shared volume and backend PVC has following naming convention `nfs-<application-pv-name>`. Below command will help to get backend PVC name
```sh
kubectl get pvc -n <openebs-namespace> -l nfs.openebs.io/nfs-pvc-name=<nfs_pvc_name> -o jsonpath='{.items[0].metadata.name}'
```
- Wait till success expansion of backend PVC i.e `.status.capacity.storage` should match with `spec.resources.requests.storage`
```sh
kubectl get pvc <backend-pvc-name> -n <openebs-namespace>
```
- Update the NFS PV capacity manually(Since resize is not supported natively by dynamic-nfs provisioner this step will be a workaround)
```sh
kubectl patch pv <nfs-pv-name> -p '{"spec": {"capacity": {"storage": "2Gi"}}}'
```
- Update the NFS PVC capacity
```sh
kubectl patch pvc <nfs-pvc-name> -n <nfs-pvc-namespace> -p '{"spec": {"resources": {"requests": {"storage": "10Gi"}}}}'
```

### Example

Example to show how to expanding NFS volumes for an already existing StorageClass(backend & NFS StorageClass), you can edit the StorageClass to include the `allowVolumeExpansion: true` if it is not marked for allowVolumeExpansion.

- Below YAML shows detailed information about backend StorageClass
```yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
creationTimestamp: "2021-09-09T08:21:34Z"
name: openebs-lvmpv
parameters:
storage: lvm
vgpattern: ^lvm$
provisioner: local.csi.openebs.io
reclaimPolicy: Delete
volumeBindingMode: Immediate
allowVolumeExpansion: true
```
- Below YAML shows detailed information about NFS StorageClass
```yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
annotations:
cas.openebs.io/config: |
- name: NFSServerType
value: "kernel"
- name: BackendStorageClass
value: "openebs-lvmpv"
openebs.io/cas-type: nfsrwx
creationTimestamp: "2021-09-09T08:23:39Z"
provisioner: openebs.io/nfsrwx
reclaimPolicy: Delete
volumeBindingMode: Immediate
allowVolumeExpansion: true
```
- Below are the details of Wordpress application consuming `RWX` volume

```sh
kubectl get pvc -n wordpress
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
wordpress-persistent-storage Bound pvc-5a8bb1f2-c183-44a7-aa70-12f3138e2a72 1Gi RWX openebs-rwx 75m
kubectl get po -n wordpress
NAME READY STATUS RESTARTS AGE
wordpress-6db6fb5444-5vj52 1/1 Running 0 76m
kubectl get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE
pvc-5a8bb1f2-c183-44a7-aa70-12f3138e2a72 1Gi RWX Delete Bound wordpress/wordpress-persistent-storage openebs-rwx 77m
```
- Backend PVC details for above `RWX` volume
```sh
kubectl get pvc -n openebs
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE
nfs-pvc-5a8bb1f2-c183-44a7-aa70-12f3138e2a72 Bound pvc-2134156f-681e-456b-b6cb-802f754a420f 1Gi RWO openebs-lvmpv 85m
```
- To Resize the backend PVC, edit the PVC capacity `spec.resources.requests.storage` to 3Gi. It may take few seconds to update the actual size in PVC resource, wait for the updated capacity to reflect in PVC status(`pvc.status.capacity.storage`). We can look at events of PVC to know information about resize:
```sh
kubectl patch pvc nfs-pvc-5a8bb1f2-c183-44a7-aa70-12f3138e2a72 -n openebs -p '{"spec": {"resources": {"requests": {"storage": "3Gi"}}}}'
persistentvolumeclaim/nfs-pvc-5a8bb1f2-c183-44a7-aa70-12f3138e2a72 patched
```
```sh
kubectl describe pvc -n openebs nfs-pvc-5a8bb1f2-c183-44a7-aa70-12f3138e2a72
...
...
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Resizing 72s (x2 over 67m) external-resizer local.csi.openebs.io External resizer is resizing volume pvc-2134156f-681e-456b-b6cb-802f754a420f
Warning ExternalExpanding 72s (x2 over 67m) volume_expand Ignoring the PVC: didn't find a plugin capable of expanding the volume; waiting for an external controller to process this PVC.
Normal FileSystemResizeRequired 72s (x2 over 67m) external-resizer local.csi.openebs.io Require file system resize of volume on node
Normal FileSystemResizeSuccessful 6s (x2 over 66m) kubelet MountVolume.NodeExpandVolume succeeded for volume "pvc-2134156f-681e-456b-b6cb-802f754a420f"
```
- Update the NFS PV capacity by running following command
```sh
kubectl patch pv pvc-5a8bb1f2-c183-44a7-aa70-12f3138e2a72 -p '{"spec": {"capacity": {"storage": "3Gi"}}}'
```
- Now, exec into the wordpress application pod(RWX volume consumer) and check the mount point Available space
```sh
root@wordpress-6db6fb5444-5vj52:/var/www/html# df -h
Filesystem Size Used Avail Use% Mounted on
overlay 916G 71G 798G 9% /
tmpfs 64M 0 64M 0% /dev
tmpfs 7.8G 0 7.8G 0% /sys/fs/cgroup
/dev/sda2 916G 71G 798G 9% /etc/hosts
shm 64M 0 64M 0% /dev/shm
----------------------------------------------------------------------
10.0.0.180:/ 3.0G 29M 2.9G 1% /var/www/html |
----------------------------------------------------------------------
tmpfs 14G 12K 14G 1% /run/secrets/kubernetes.io/serviceaccount
```

Above output shows NFS volume has successfully expanded.

<br></br>

**Gotcha**: NFS PVC will still report old capacity, once dynamic-nfs-provisioner shifts towards CSI it can support dynamically expanding RWX volume.

<br></br>

#### Tip

- Download and run [script](./get-nfs-volume-details.sh) by passing NFS PVC name & namespace as input arguments to test and
it will display backend PVC & PV details for given NFS PVC
```sh
./get-nfs-volume-details.sh wordpress-persistent-storage wordpress
----------------------------------------------------------------
Backend PVC Name: nfs-pvc-5a8bb1f2-c183-44a7-aa70-12f3138e2a72
Backend PVC Namespace: openebs
Backend PV Name: pvc-2134156f-681e-456b-b6cb-802f754a420f
NFS PV Name: pvc-5a8bb1f2-c183-44a7-aa70-12f3138e2a72
NFS PVC Namespace/Name: wordpress/wordpress-persistent-storage
```

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