Load Balancer

Ref: https://metallb.universe.tf/

In lieu of having a physical load balancer, this cluster will use MetalLB as a load balancer. In my network, I have a block of IP addresses reserved for DHCP, and picked a range of IPs to use for load balancer IPs in the cluster.

The first thing to do, is to get the latest release of MetalLB:

cd ~/workspace/picluster
poetry shell

mkdir -p ~/workspace/picluster/metallb
cd ~/workspace/picluster/metallb
MetalLB_RTAG=$(curl -s https://api.github.com/repos/metallb/metallb/releases/latest|grep tag_name|cut -d '"' -f 4|sed 's/v//')
echo $MetalLB_RTAG
0.13.12

Obtain the version, install it, and wait for everything to come up:

wget https://raw.githubusercontent.com/metallb/metallb/v${MetalLB_RTAG}/config/manifests/metallb-native.yaml -O metallb-native-${MetalLB_RTAG}.yaml

kubectl apply -f metallb-native-${MetalLB_RTAG}.yaml
kubectl get pods -n metallb-system --watch
kubectl get all -n metallb-system

Everything should be running, but needs to be configured for this cluster. Specifically, we need to setup and advertise the address pool(s), which can be a CIDR, address range, and IPv4 and/or IPv6 addresses. For our case, I’m reserving 10.11.12.201 – 10.11.12.210 for load balancer IPs and using L2 advertisement (ipaddress_pool.yaml):

apiVersion: metallb.io/v1beta1
kind: IPAddressPool
metadata:
  name: production
  namespace: metallb-system
spec:
  addresses:
  - 10.11.12.201-10.11.12.210
---
apiVersion: metallb.io/v1beta1
kind: L2Advertisement
metadata:
  name: l2-advert
  namespace: metallb-system

Apply this configuration, and examine the configuration:

kubectl apply -f ipaddress_pools.yaml
ipaddresspool.metallb.io/production created
l2advertisement.metallb.io/l2-advert created

kubectl get ipaddresspools.metallb.io -n metallb-system
NAME         AUTO ASSIGN   AVOID BUGGY IPS   ADDRESSES
production   true          false             ["10.11.12.201-10.11.12.210"]

kubectl get l2advertisements.metallb.io -n metallb-system
NAME        IPADDRESSPOOLS   IPADDRESSPOOL SELECTORS   INTERFACES
l2-advert

kubectl describe ipaddresspools.metallb.io production -n metallb-system
Name:         production
Namespace:    metallb-system
Labels:       <none>
Annotations:  <none>
API Version:  metallb.io/v1beta1
Kind:         IPAddressPool
Metadata:
  Creation Timestamp:  2024-01-17T19:05:29Z
  Generation:          1
  Resource Version:    3648847
  UID:                 38491c8a-fdc1-47eb-9299-0f6626845e82
Spec:
  Addresses:
    10.11.12.201-10.11.12.210
  Auto Assign:       true
  Avoid Buggy I Ps:  false
Events:              <none>

Note: if you don’t want IP addresses auto-assigned, you can add the clause “autoAssign: false”, to the “spec:” section of the IPAddressPool.

To use the load balancer, you can change the type under the “spec:” section from ClusterIP or NodePort to LoadBalancer, by editing the configuration. For example, to change Grafana from NodePort to LoadBalancer, one would use the following to edit the configuration:

kubectl edit -n monitoring svc/prometheusstack-grafana

This is located at the bottom of the file:

...
spec:
  clusterIP: 10.233.22.171
  clusterIPs:
  - 10.233.22.171
  externalTrafficPolicy: Cluster
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  ports:
  - name: http-web
    nodePort: 32589
    port: 80
    protocol: TCP
    targetPort: 3000
  selector:
    app.kubernetes.io/instance: prometheusstack
    app.kubernetes.io/name: grafana
  sessionAffinity: None
  type: NodePort
status:
  loadBalancer: {}

When you show the service, you’ll see the load balancer IP that was assigned:

kubectl get svc -n monitoring prometheusstack-grafana
NAME                      TYPE           CLUSTER-IP      EXTERNAL-IP    PORT(S)        AGE
prometheusstack-grafana   LoadBalancer   10.233.22.171   10.11.12.201   80:32589/TCP   5d23h

Here is a sample deployment (web-demo-test.yaml) to try. IUt has the LoadBalancer type specified:

apiVersion: v1
kind: Namespace
metadata:
  name: web
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-server
  namespace: web
spec:
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: httpd
        image: httpd:alpine
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: web-server-service
  namespace: web
spec:
  selector:
    app: web
  ports:
    - protocol: TCP
      port: 80
      targetPort: 80
  type: LoadBalancer

Apply the configuration and check the IP address:

kubectl apply -f web-app-demo.yaml
kubectl get svc -n web

From the command line, you can do “curl http://IP_ADDRESS” to make sure it works. If you want a specific IP address, you can change the above web-app-demo.yaml to add the following line after the type (note the same indentation level):

  type: LoadBalancer
  loadBalancerIP: 10.11.12.205

Uninstalling MetalLB

Before removing MetalLB, you should change any services that are using it, to go back to NodePort or ClusterIP as the type. Then, delete the configuration:

kubectl delete -f metallb-native-${MetalLB_RTAG}.yaml

NGINX Ingress

Ref: https://docs.nginx.com/nginx-ingress-controller/technical-specifications/

Ref: https://kubernetes.github.io/ingress-nginx/deploy/

With Load Balancer setup and running, we’ll create an Ingress controller using NGINX. You can view the compatibility chart here to select the NGINX version desired. For our purposes, we’ll use helm chart install, so that we have sources and can delete/update CRDs. I’m currently running Kubernetes 1.28, so either 1.02 or 1.1.2 of the Helm Chart. Let’s pull the charts for 1.1.2:

cd ~/workspace/picluster/
helm pull oci://ghcr.io/nginxinc/charts/nginx-ingress --untar --version 1.1.2
cd nginx-ingress

Install NGINX Ingress with:

helm install my-nginx --create-namespace -n nginx-ingress .
NAME: my-nginx
LAST DEPLOYED: Fri Jan 19 11:14:16 2024
NAMESPACE: nginx-ingress
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
The NGINX Ingress Controller has been installed.

If you want to customize settings, you can add the “–values values.yaml” argument, after first getting the list of options using the following command, and then modifying them:

helm show values ingress-nginx --repo https://kubernetes.github.io/ingress-nginx > values.yaml

The NGINX service will have an external IP address, as the type is LoadBalancer, and MetalLB will assign an address from the pool (note: you can specify an IP to use in values.yaml).

To test this out, we’ll great a web based app:

kubectl create deployment demo --image=httpd --port=80
kubectl expose deployment demo

We can then create an ingress entry for a local (dummy) domain and forward port 8080 to the default port (80) for the app:

kubectl create ingress demo-localhost --class=nginx --rule="demo.localdev.me/*=demo:80"
kubectl port-forward --namespace=nginx-ingress service/my-nginx-nginx-ingress-controller 8080:80 &

To test this out, you can try accessing the URL:

curl http://demo.localdev.me:8080
Handling connection for 8080
<html><body><h1>It works!</h1></body></html>

If you have a publicly visible domain, you can forward that to the app. I have not tried it, but it looks like the ingress command would look like:

kubectl create ingress demo --class=nginx  --rule YOUR.DOMAIN.COM/=demo:80

TODO: Setting up certificates? authentication?

Upgrading NGINX Ingress (not tried)

You must manually update the CRDs, before upgrading NGINX. Pull the new release and then apply the updated CRDs:

cd ~/workspace/picluster
helm pull oci://ghcr.io/nginxinc/charts/nginx-ingress --untar --version VERSION_DESIRED
cd nginx-ingress
kubectl apply -f crds/

You may see this warning, but it can be ignored:

Warning: kubectl apply should be used on resource created by either kubectl create --save-config or kubectl apply

You should check the release notes, for any other specific actions needed for a new release. You can then upgrade NGINX:

helm upgrade my-nginx .

FYI: At the bottom of the NGINX install page, there are notes on how to upgrade without downtime.

Uninstalling NGINX Ingress

To uninstall, remove the CRDs and then uninstall with Helm, using the name specified, when the cluster was created:

kubectl delete -f ~/workspace/picluster/nginx-ingress/crds/
helm uninstall my-nginx -n nginx-ingress

For monitoring of the cluster and logs, we’ll setup several tools…

Prometheus/Grafana

First, we’ll create a login account for accessing (Grafana) UI. Create area and build password to store in a secret:

cd ~/workspace/picluster
poetry shell

mkdir -p ~/workspace/picluster/monitoring/kube-prometheus-stack
cd ~/workspace/picluster/monitoring/kube-prometheus-stack/
kubectl create namespace monitoring
echo -n ${USER} > ./admin-user
echo -n 'PASSWORD' > ./admin-password # Change to desired password
kubectl create secret generic grafana-admin-credentials --from-file=./admin-user --from-file=admin-password -n monitoring
rm admin-user admin-password

Add the helm repo:

helm repo add prometheus-community https://prometheus-community.github.io/helm-charts
helm repo update

Install kube-prometheus-stack with the credentials we selected, and using Longhorn for persistent storage (allocating 50GB):

helm install prometheusstack prometheus-community/kube-prometheus-stack --namespace monitoring \
  --set prometheus.prometheusSpec.storageSpec.volumeClaimTemplate.spec.storageClassName="longhorn" \
  --set prometheus.prometheusSpec.storageSpec.volumeClaimTemplate.spec.accessModes[0]="ReadWriteOnce" \
  --set prometheus.prometheusSpec.storageSpec.volumeClaimTemplate.spec.resources.requests.storage="50Gi" \
  --set grafana.admin.existingSecret=grafana-admin-credentials

Wait for everything to come up with either of these:

kubectl --namespace monitoring get pods -l "release=prometheusstack"
kubectl get all -n monitoring

At this point, you can look at the Longhorn console, and see that there is a 50GB volume created for Prometheus/Grafana. As with any Helm install, you can get the values used for the chart with the following command and then do a helm update with the -f option and the updated yaml file:

helm show values prometheus-community/kube-prometheus-stack > values.yaml

Next, change the Grafana UI from ClusterIP to NodePort (or LoadBalancer, if you have set that up):

kubectl edit -n monitoring svc/prometheusstack-grafana

From a browser, you can use a node port IP and the port shown in the service output to access the UI and log in with the credentials you created in the above steps:

NAME                                               TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)                      AGE
service/alertmanager-operated                      ClusterIP   None            <none>        9093/TCP,9094/TCP,9094/UDP   5m34s
service/prometheus-operated                        ClusterIP   None            <none>        9090/TCP                     5m33s
service/prometheusstack-grafana                    NodePort    10.233.22.171   <none>        80:32589/TCP                 5m44s
...

For example, “http://10.11.12.190:32589” in this example. There will already be a data source set up for Prometheus, and you can use this to examine the cluster. Under Dashboards, there are some predefined dashboards, and you can also make your own and obtain others and import them.

I found this one, from David Calvert (https://github.com/dotdc/grafana-dashboards-kubernetes.git), with some nice dashboards for nodes, pods, etc. I cloned the repo to my monitoring directory, and then from the Grafana UI, clicked on the plus sign at the top of the main Grafana page and selected “Import Dashboard”, clicked on the dag/drop pane, navigated to one of the dashboard json files – the k8s-views-global.json is nice, selected the predefined “Prometheus” data source, and clicked “Import”. This gives a screen with info on the nodes, network, etc.

TODO: Setting up Prometheus to use HTTPS only.

LOKI

For log aggregation, we can install Loki, persisting information to longhorn. I must admit, I struggled getting this working and, although repeatable, there may be better ways to get this working:

helm repo add grafana https://grafana.github.io/helm-charts
helm repo update
helm upgrade --install loki grafana/loki-stack \
  --namespace monitoring \
  --set loki.persistence.enabled=true \
  --set loki.persistence.storageClassName=longhorn \
  --set loki.persistence.size=20Gi \
  --set 'promtail.tolerations[0].key=CriticalAddonsOnly' \
  --set 'promtail.tolerations[0].operator=Exists' \
  --set 'promtail.tolerations[0].effect=NoExecute' \
  --set 'promtail.tolerations[1].key=node-role.kubernetes.io/control-plane' \
  --set 'promtail.tolerations[1].operator=Exists' \
  --set 'promtail.tolerations[1].effect=NoSchedule'

You can check the monitoring namespace, to wait for the promtail pods to be running on each node. Once running, you can access the Grafana UI and create a new datasource, selecting the type “Loki”. For the URL, use “http://loki:3100” and click save and test. I’m not sure why the Helm install didn’t automatically create the source, and why this manual source creation fails on the “test” part of the save and test, but the source is now there and seems to work.

To use, you can go to the Explore section, and provide a query. With the “builder” (default query mode), you can select the label type (e.g. “pod”) and then the instance you are interested in. You can also change from “builder” to “code” and enter this as the query and run the query:

{stream=”stderr”} |= `level=error`

This will show error logs from all nodes. For example (clicking on “>” symbol at left to expand entry to show the fields:

Another query that reports errors over a period of five minutes is:

count_over_time({stream="stderr"} |= `level=error` [5m])

Customizing Logging Aggregation

You can customize the promtail pod’s configuration file so that you can do queries on custom labels, instead of searching for specific text in log messages. To do that, we first obtain the promtail configuration:

cd ~/workspace/picluster/monitoring
kubectl get secret -n monitoring loki-promtail -o jsonpath="{.data.promtail\.yaml}" | base64 --decode > promtail.yaml

Edit this file, and under the “scrape_configs” section, you will see “pipeline_stages”:

scrape_configs:
  # See also https://github.com/grafana/loki/blob/master/production/ksonnet/promtail/scrape_config.libsonnet for reference
  - job_name: kubernetes-pods
    pipeline_stages:
      - cri: {}
    kubernetes_sd_configs:

We will add a new stage called “- match”, under the “- cri:” line. To do the matching for a app called “api” we use TODO: Have a app with JSON and then describe the process. Use https://www.youtube.com/watch?v=O52dseg2bJo&list=TLPQMjkxMTIwMjOvWB8m2JEG4Q&index=7 for reference.

Uninstalling

To remove Prometheus and Grafana you must remove several CRDs,helm uninstall, and remove the secret:

kubectl delete crd alertmanagerconfigs.monitoring.coreos.com
kubectl delete crd alertmanagers.monitoring.coreos.com
kubectl delete crd podmonitors.monitoring.coreos.com
kubectl delete crd probes.monitoring.coreos.com
kubectl delete crd prometheusagents.monitoring.coreos.com
kubectl delete crd prometheuses.monitoring.coreos.com
kubectl delete crd prometheusrules.monitoring.coreos.com
kubectl delete crd scrapeconfigs.monitoring.coreos.com
kubectl delete crd servicemonitors.monitoring.coreos.com
kubectl delete crd thanosrulers.monitoring.coreos.com

helm uninstall -n monitoring prometheus-stack
kubectl delete secret -n monitoring grafana-admin-credentials

Top remove Loki, you can helm uninstall:

helm uninstall -n monitoring loki

To clean up anything else that remains, you can remove the namespace:

kubectl delete ns monitoring

We will use Velero to perform full or partial backup and restore of the cluster and will use Minio to provide a local S3 storage areas on another computer on the network (I just used my Mac laptop, but you could use a server or multiple servers instead), to be able to do scheduled backups with Velero.

Minio

On the Mac, you can use brew to install Minio and the Minio client (mc):

brew upgrade
brew install minio/stable/minio
brew install minio/stable/mc

Create an area for data storage and an area for Minio:

cd ~/workspace/picluster
poetry shell
cd mkdir -p ~/workspace/minio-data
mkdir -p ~/workspace/picluster/minio

In the ~/workspace/picluster/minio/minio.cfg create this file with the user/password desired(default is minioadmin/minioadmin) and host name (or IP) where server will run (in this example, I use my laptop name):

# MINIO_ROOT_USER and MINIO_ROOT_PASSWORD sets the root account for the MinIO server.
# This user has unrestricted permissions to perform S3 and administrative API operations on any resource in the deployment.
# Omit to use the default values 'minioadmin:minioadmin'.
# MinIO recommends setting non-default values as a best practice, regardless of environment

MINIO_ROOT_USER=minime
MINIO_ROOT_PASSWORD=PASSWORD_YOU_WANT_HERE

# MINIO_VOLUMES sets the storage volume or path to use for the MinIO server.

MINIO_VOLUMES="~/workspace/minio-data"

# MINIO_SERVER_URL sets the hostname of the local machine for use with the MinIO Server
# MinIO assumes your network control plane can correctly resolve this hostname to the local machine

# Uncomment the following line and replace the value with the correct hostname for the local machine and port for the MinIO server (9000 by default).

MINIO_SERVER_URL="http://triunity.home:9000"

Note: There is no way to change the user/password, from the console later.

Create a minio-credentials file with the same user name and password as was done in the minio.cfg file:

[default]
aws_access_key_id = minime
aws_secret_access_key = SAME_PASSWORD_AS_ABOVE

I did “chmod 700” for both minio.cfg and minio-credentials.

Next, create a script(minio-server-start) to start up Minio with the desired settings:

export MINIO_CONFIG_ENV_FILE=./minio.cfg
minio server --console-address :9090 &

When you run this script, it will output will indicate a warning that the local host has all the data and a failure will cause loss of data (duh). It will show the URL for API (port 9000) and console (port 9090), along with the username and password to access. Near the bottom, it will show you an alias command that you should copy and paste. It names the server and provides credentials info. It looks like:

mc alias set 'myminio' 'http://trinity.home:9000' 'minime' 'THE_PASSWORD_FROM CONFIG'

Then do the following to make sure that the server is running the latest code:

mc admin update myminio

In your browser, go to the URL and log in with the username/password. Under Administrator -> Buckets menu on the left panel, create a bucket called “kubernetes”. I haven’t tried, but you can turn on versioning, object locking, and quota.

Velero

Ref: https://velero.io/docs/main/contributions/minio/

For the Mac, use brew to install Velero and either note the version or check with the list command (in my case it has 1.12.3):

brew install velero
brew list velero

You can check compatibility of the Velero version you have and the kubernetes version running (and adjust the version used by brew, if needed). The matrix is here. (Optionally) Pull the Velero sources from git, so that we can use examples and have documentation:

cd ~/workspace/picluster
git clone https://github.com/vmware-tanzu/velero.git
cd velero

In the README.md, it will have version compatibility info.

It indicates that velero 1.12.x works with Kubernetes 1.27.3 and 1.13.x with Kubernetes 1.28.3. We have 1.28 Kubernetes, but there is no brew version for Velero 1.13 right now, so we’ll hope 1.12.3 Velero works.

We need the Velero plugin for AWS. The plugins are shown here. For Velero 1.12.x, we need AWS plugin 1.8.x. The plugin tags show that v1.8.2 is the latest.

Next, start up Velero, specifying the plugin version to use, the bucket name you created in Minio (“kubernetes”), the credentials file, Minio as the S3 storage, and the Minio API URL (your host name with port 9000):

velero install \
    --provider aws \
    --plugins velero/velero-plugin-for-aws:v1.8.2 \
    --bucket kubernetes \
    --secret-file ~/workspace/picluster/minio/minio-credentials \
    --use-volume-snapshots=false \
    --backup-location-config region=minio,s3ForcePathStyle="true",s3Url=http://trinity.home:9000

It will display that Velero is installed and that you can use “kubectl logs deployment/velero -n velero” to see the status.

Check that the backup location is available with:

velero backup-location get
NAME      PROVIDER   BUCKET/PREFIX   PHASE       LAST VALIDATED                  ACCESS MODE   DEFAULT
default   aws        kubernetes      Available   2024-01-16 13:15:52 -0500 EST   ReadWrite     true

If you have the Velero git repo pulled, as mentioned above, you can start an example:

cd ~/workspace/picluster/velero
kubectl apply -f examples/nginx-app/base.yaml

kubectl get all -n nginx-example
NAME                                    READY   STATUS    RESTARTS   AGE
pod/nginx-deployment-75b696dc55-25d6r   1/1     Running   0          66s
pod/nginx-deployment-75b696dc55-7h5zx   1/1     Running   0          66s

NAME               TYPE           CLUSTER-IP     EXTERNAL-IP   PORT(S)        AGE
service/my-nginx   LoadBalancer   10.233.46.15   <pending>     80:30270/TCP   66s

NAME                               READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/nginx-deployment   2/2     2            2           66s

NAME                                          DESIRED   CURRENT   READY   AGE
replicaset.apps/nginx-deployment-75b696dc55   2         2         2       66s

You should see the deployment running (Note: there is no external IP, as I don’t have a load balancer running right now). If you want to just backup this application, you can do:

velero backup create nginx-backup --selector app=nginx
velero backup get
NAME           STATUS      ERRORS   WARNINGS   CREATED                         EXPIRES   STORAGE LOCATION   SELECTOR
nginx-backup   Completed   0        0          2024-01-16 13:22:53 -0500 EST   29d       default            app=nginx

velero backup describe nginx-backup
velero backup logs nginx-backup

If you look at the “kubernetes” bucket from the Minio console, you’ll see the backup files there. Now, we can delete the application and then restore it…

kubectl delete namespace nginx-example
kubectl get all -n nginx-example
No resources found in nginx-example namespace.

velero restore create --from-backup nginx-backup
Restore request "nginx-backup-20240116132642" submitted successfully.
Run `velero restore describe nginx-backup-20240116132642` or `velero restore logs nginx-backup-20240116132642` for more details.
(picluster-py3.11) pcm@trinity:~/workspace/picluster/velero$ kubectl get all -n nginx-example
NAME                                    READY   STATUS    RESTARTS   AGE
pod/nginx-deployment-75b696dc55-25d6r   1/1     Running   0          3s
pod/nginx-deployment-75b696dc55-7h5zx   1/1     Running   0          3s

NAME               TYPE           CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
service/my-nginx   LoadBalancer   10.233.16.165   <pending>     80:31834/TCP   3s

NAME                               READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/nginx-deployment   2/2     2            2           2s

NAME                                          DESIRED   CURRENT   READY   AGE
replicaset.apps/nginx-deployment-75b696dc55   2         2         2       3s

You can backup the full cluster with “velero backup create FULL_BACKUP-2024-01-17”, using a name to denote the backup. You can use “velero backup get” to see a list of backups, and “velero restore get” to see a list of restores. You can even schedule backups with a command, like the following:

velero schedule create homek8s --schedule="@every 6h"

I haven’t tried this, because I’m using my laptop, which is not always on.

Uninstalling

First, we’ll delete the NGINX app that was installed, and the corresponding Velero backup.

kubectl delete -f examples/nginx-app/base.yaml
velero backup delete nginx-backup
velero restore delete nginx-backup

You can check in Minio to make sure the backups are gone. Next, Velero can be removed from the cluster, along with the CRDs used:

kubectl delete namespace/velero clusterrolebinding/velero
kubectl delete crds -l component=velero

Lastly, you can delete the “kubernetes” bucket from the Minio console, and kill the Minio process.

Side Bar

I did have a problem at one point (may have been due to an older Minio version), where I deleted a backup from Velero, and it later re-appeared when doing “velero backup get”. I looked at operations with “mc admin trace myminio” and saw that requests were coming into Minio to remove the backup from my “myminio” server, but the bucket was NOT being removed. Velero would later sync with Minio, see the backup and show that it was still there on a later “velero backup get” command.

I found that the following would remove the bucket and everything under:

mc rm --recursive kubernetes --force --dangerous

There is also a “mc rb” command to remove the bucket (have not tried), or an individual backup can be removed with “mc rm RELATIVE/PATH/FROM/BUCKET”, like “kubernetes/backups/nginx-backup” and “kubernetes/restores/nginx-backup-20231205150432”. I think I tried doing it from the Minio UI, but the files were not removed. My guess is that it does an API request to remove the file, just like what Velero does, whereas the command line seems to remove the file.

There are many shared storage products available for Kubernetes. I had settled on Longhorn, as it provides block storage, is pretty easy to setup, has snapshots, is distributed, and allows backup to secondary storage (I plan on using NFS to backup to a NAS box that I have on my network). As of this writing, the latest is 1.5.3 (https://longhorn.io/).

Preparation

With the 1TB SSD drives on each Raspberry PI, and the /dev/sda7 partition, mounted as /var/lib/longhorn, the RPIs can be prepared for Longhorn. There is a script that can be used to see if all the dependencies have been met on the nodes. For 1.5.3 run:

curl -sSfL https://raw.githubusercontent.com/longhorn/longhorn/v1.5.3/scripts/environment_check.sh | bash

If there are any errors, you need to address them, before continuing. For example, if it complains that iscsid is missing on a node, you can do:

sudo apt-get reinstall -f open-iscsi
sudo systemctl enable iscsid
sudo systemctl start iscsid
kubectl apply -f https://raw.githubusercontent.com/longhorn/longhorn/v1.5.3/deploy/prerequisite/longhorn-iscsi-installation.yaml

You should make sure that the longhorn-iscsi-installation pods are running on all nodes. In my case, one was not, and the log for the iscsi-installation container was saying that module iscsi_tcp was not present. For that, I did the following:

sudo apt install linux-modules-extra-raspi
sudo reboot

I’ve added that package to tools setup in Part IV, so that it will be already present.

If multipathd is enabled, which is a security risk for block storage devices, you can handle that with:

sudo systemctl stop multipathd
sudo systemctl disable multipathd

In my run, I had a node, apoc, with missing package:

[INFO]  Required dependencies 'kubectl jq mktemp sort printf' are installed.
[INFO]  All nodes have unique hostnames.
[INFO]  Waiting for longhorn-environment-check pods to become ready (0/5)...
[INFO]  Waiting for longhorn-environment-check pods to become ready (0/5)...
[INFO]  All longhorn-environment-check pods are ready (5/5).
[INFO]  MountPropagation is enabled
[INFO]  Checking kernel release...
[INFO]  Checking iscsid...
[INFO]  Checking multipathd...
[INFO]  Checking packages...
[ERROR] nfs-common is not found in apoc.
[INFO]  Checking nfs client...
[INFO]  Cleaning up longhorn-environment-check pods...
[INFO]  Cleanup completed.

I did a “sudo apt install nfs-common -y” on that node. Since then, I’ve added that to the RPI tools setup in Part IV, so that it’ll be there. Re-run the script to make sure that all the nodes are ready for install.

Install

Helm has already been installed on my Mac, so we can obtain Longhorn with:

helm repo add longhorn https://charts.longhorn.io
helm repo update

Setup an area and get the current settings for Longhorn, so that we can customize them:

cd ~/workspace/picluster
poetry shell
cd mkdir ~/workspace/picluster/longhorn
cd ~/workspace/picluster/longhorn

Before installing, we’ll pull down the settings for v1.5.3:

curl -o values-1.5.3.yaml https://raw.githubusercontent.com/longhorn/longhorn/v1.5.3/chart/values.yaml

In values-1.5.3.yaml, under the section service:, for ui: type, set type to NodePort. Under the section persistence:, set the ReclaimType to Retain:

75c75
<     type: ClusterIP
---
>     type: NodePort
89c89
<   reclaimPolicy: Delete
---
>   reclaimPolicy: Retain

This will allow you to access the UI by using any node’s IP, and when Longhorn is brought down, the files in block storage are retained.

We also need to set tolerations for the manager, UI, and driver. There are instructions in the values.yaml file where you remove the square brackets and un-comment the toleration settings. If you don’t do this, the longhorn-driver-deployment pod will never get out of Init state. Diffs for just the tolerations will look like:

--- a/longhorn/values-1.5.3.yaml
+++ b/longhorn/values-1.5.3.yaml
@@ -182,13 +182,13 @@ longhornManager:
     ## Allowed values are `plain` or `json`.
     format: plain
   priorityClass: ~
-  tolerations: []
+  tolerations:
   ## If you want to set tolerations for Longhorn Manager DaemonSet, delete the `[]` in the line above
   ## and uncomment this example block
-  # - key: "key"
-  #   operator: "Equal"
-  #   value: "value"
-  #   effect: "NoSchedule"
+  - key: "key"
+    operator: "Equal"
+    value: "value"
+    effect: "NoSchedule"
   nodeSelector: {}
   ## If you want to set node selector for Longhorn Manager DaemonSet, delete the `{}` in the line above
   ## and uncomment this example block
@@ -202,13 +202,13 @@ longhornManager:

 longhornDriver:
   priorityClass: ~
-  tolerations: []
+  tolerations:
   ## If you want to set tolerations for Longhorn Driver Deployer Deployment, delete the `[]` in the line above
   ## and uncomment this example block
-  # - key: "key"
-  #   operator: "Equal"
-  #   value: "value"
-  #   effect: "NoSchedule"
+  - key: "key"
+    operator: "Equal"
+    value: "value"
+    effect: "NoSchedule"
   nodeSelector: {}
   ## If you want to set node selector for Longhorn Driver Deployer Deployment, delete the `{}` in the line above
   ## and uncomment this example block
@@ -218,13 +218,13 @@ longhornDriver:
 longhornUI:
   replicas: 2
   priorityClass: ~
-  tolerations: []
+  tolerations:
   ## If you want to set tolerations for Longhorn UI Deployment, delete the `[]` in the line above
   ## and uncomment this example block
-  # - key: "key"
-  #   operator: "Equal"
-  #   value: "value"
-  #   effect: "NoSchedule"
+  - key: "key"
+    operator: "Equal"
+    value: "value"
+    effect: "NoSchedule"
   nodeSelector: {}
   ## If you want to set node selector for Longhorn UI Deployment, delete the `{}` in the line above
   ## and uncomment this example block

Install Longhorn with the updated values and monitor the namespace until you see that everything is up:

helm install longhorn longhorn/longhorn --namespace longhorn-system --create-namespace --version 1.5.3  --values values-1.5.3.yaml
kubectl get all -n longhorn-system

Use “kubectl get service -n longhorn-system” to find the port for the frontend service, and then with a browser you can access the UI using one of the node’s IPs and the port. For example, http://10.11.12.188:30191, on one run that I did.

You can see and manage volumes, view the total amount of disk space and what is scheduled, and see the nodes being used and their state.

Creating Persistent Volume Claim Using Longhorn as Storage

As an example, we can create a PVC that uses Longhorn for storage:

cat << EOF | kubectl create -f -
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: myclaim
spec:
  accessModes:
    - ReadWriteMany
  volumeMode: Filesystem
  resources:
    requests:
      storage: 2Gi
EOF

You can verify that the PVC is using longhorn for storage, by doing:

kubectl get pvc
NAME      STATUS   VOLUME                                     CAPACITY   ACCESS MODES   STORAGECLASS   AGE
myclaim   Bound    pvc-89456753-e271-46a0-b8c0-9e53affc4c6b   2Gi        RWX            longhorn       3s

The storage class shows “longhorn”. From the Longhorn console, you can see that there is a detached volume for that PVC.

Next, you can create a pod that uses the PVC. Here is an example, using NGINX:

cat << EOF |kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
    - name: myfrontend
      image: nginx
      volumeMounts:
      - mountPath: "/var/foo/"
        name: mypd
  volumes:
    - name: mypd
      persistentVolumeClaim:
        claimName: myclaim
EOF

This specifies the PVC “myclaim”, and you can see that there is a PV created that uses the PVC, has reclaim policy of retain, and uses the longhorn storage class:

kubectl get pv
NAME                                       CAPACITY   ACCESS MODES   RECLAIM POLICY   STATUS   CLAIM             STORAGECLASS   REASON   AGE
pvc-89456753-e271-46a0-b8c0-9e53affc4c6b   2Gi        RWX            Retain           Bound    default/myclaim   longhorn                4m35s

Bonus Points

You can setup a backup for the Longhorn storage. In my case, I have a NAS box that is accessible via NFS.

The first step is to create a share area on the device. You can follow whatever instructions youhave for creating a NFS share.

On my NAS (using GUI console), I created a share at /longhorn, with R/W access for my account (I’m in the “administ” group, BTW) and “no squash users” set. I set the IP range to 10.11.12.0/24, so only nodes from network can access this share. I made sure that the shared area exists, has 777 perms, user/group set to admin. NOTE: Is is actually at /share/CACHEDEV1_DATA/longhorn and there is a symlink at /share/longhorn. I created a subdirectory called “backups” in this area (so there can be other sub-directories for other shares, if desired).

I checked that it appears under /etc/exports with the subnet called out and the settings desired:

"/share/CACHEDEV1_DATA/longhorn" 10.11.12.0/24(sec=sys,rw,async,wdelay,insecure,no_subtree_check,no_root_squash,fsid=...)

I checked that the share was set up correctly, by mounting it from a node and creating/changing a file:

sudo mount -t nfs <IP OF NAS>:/longhorn /mnt

Now, Longhorn can be configured to use this NFS share for backups. Use helm to install the NFS provisioner for Longhorn.

helm repo add nfs-subdir-external-provisioner https://kubernetes-sigs.github.io/nfs-subdir-external-provisioner/
helm repo update

You can see the configuration for the provisioner with:

helm show values -n nfs-storage nfs-subdir-external-provisioner/nfs-subdir-external-provisioner

Install the provisioner, setup for your share, using the IP of your NFS server:

helm install nfs-subdir-external-provisioner nfs-subdir-external-provisioner/nfs-subdir-external-provisioner –set nfs.server=<IP_OF_NFS_SERVER> –set nfs.path=/longhorn/backup -n nfs-storage –create-namespace

Under the Longhorn UI (accessible via NodePort), go to Settings, and in the Backup Target, set the path to the NFS share and click the SAVE button at the bottom of the page:

nfs://<IP_OF_NFS_SERVER>:/longhorn/backup/

Once you have created a volume and it is attached to a node, you can do a backup or take a snapshot. Form the Volume section, click on the name of a volume to bring up details, and then you can click on “Take Snapshot” or “Create Backup”. You can go back to older versions of snapshots, by detaching volume and attaching with maintenance checked. From the snapshot, you can check revert and then detach and re-attach w/o maintenance. Once healthy, you can see that the snapshot is there.

Uninstalling

To remove Longhorn, you must set a flag to allow deletion, before removing:

kubectl -n longhorn-system patch -p '{"value": "true"}' --type=merge lhs deleting-confirmation-flag
helm uninstall longhorn -n longhorn-system

Side Bar

Kernel Upgrades

If you ever update your kernel on the Raspberry PI, you’ll need to reinstall the extra modules. You can do this with:

sudo apt-get reinstall linux-modules-extra-$(uname -r)

Reboot afterwards. If you don’t do this install, features like Longhorn will be missing required modules and fail.

Expanding Longhorn Volume Size

The Longhorn documentation has information on expanding a volume.