Hello K8s: Resource Management

This is the second post from the series of K8s lab/dev setup, previous we installed the container engine and setup kubeadm. This post cover ingress and storage resource management along with Kubernetes Dashboard deployment, allowing manage the platform using an web application. I actually don't use much the Dashboard but that could be useful to have and help understand K8s components.

Storage

While most common workloads is stateless, running stateful services is the core feature of an application. Containers have ephemeral storage which means the data is lost when the container shutdown, to provide an persistent storage in K8s we need have an StorageClass (opens in a new tab) implementation and then describe an Volume (opens in a new tab), we can attach the volume directly or claim it by PersistentVolumeClaim (opens in a new tab). The earlier K8s version the recommend approach was having an persistent service setup outside of K8s because of the complexity to bring persistence services like databases however with the new storage design this complexity drop significantly.

Here we will have two StorageClass implementation, thew first one is manual for the case we wanna specify the path where the files will be persisted and the second case is local-path with local-path-provisioner where we just claim an volume, that dynamically create a local path for us.

For the manual storage setup just run:

kubectl create -f https://raw.githubusercontent.com/rodrigobaron/manifests/main/manual-storage/deployment.yaml

The local-path-provisioner it's an Rancher project (opens in a new tab) to make possible use node storage in the workloads. We create it by running:

kubectl create -f https://raw.githubusercontent.com/rodrigobaron/manifests/main/local-path-storage/deployment.yaml

To verify if is all working we can check the status:

kubectl -n local-path-storage get pod

And define local-pathas default storage:

kubectl patch storageclass local-path -p '{"metadata": {"annotations": {"storageclass.kubernetes.io/is-default-class": "true"}}}'

We can check it listing the StorageClass objects:

kubectl get sc
NAME                   PROVISIONER                    RECLAIMPOLICY   VOLUMEBINDINGMODE      ALLOWVOLUMEEXPANSION   AGE
local-path (default)   rancher.io/local-path          Delete          WaitForFirstConsumer   false                  38s
manual                 kubernetes.io/no-provisioner   Delete          WaitForFirstConsumer   false                  2m5s

Ingress Controller

Ingress is the component which exposes the HTTP and HTTPS routes from outside the cluster by defined rules. Ingress controller is responsible to route the network to Ingress usually using a load balance handled by a proxy technologies such as Envoy, NGINX or HAProxy. I'll use ingress-nginx (opens in a new tab) and install as follows:

kubectl create -f https://raw.githubusercontent.com/rodrigobaron/manifests/main/ingress-nginx/deploy.yaml

This deployment use a modified version to allow host network that was done by editing ingress-nginx-controller deployment:

template:
    metadata:
      labels:
        app.kubernetes.io/name: ingress-nginx
        app.kubernetes.io/instance: ingress-nginx
        app.kubernetes.io/component: controller
    spec:
      hostNetwork: true

To check if all is running just run the command below and wait few minutes until all is ready:

kubectl get pods -n ingress-nginx -l app.kubernetes.io/name=ingress-nginx

After the controller is ready we ca check the version by running:

POD_NAMESPACE=ingress-nginx
POD_NAME=$(kubectl get pods -n $POD_NAMESPACE -l app.kubernetes.io/name=ingress-nginx --field-selector=status.phase=Running -o jsonpath='{.items[0].metadata.name}')
kubectl exec -it $POD_NAME -n $POD_NAMESPACE -- /nginx-ingress-controller --version

Should output something like this:

-------------------------------------------------------------------------------
NGINX Ingress controller
  Release:       v1.0.4
  Build:         9b78b6c197b48116243922170875af4aa752ee59
  Repository:    https://github.com/kubernetes/ingress-nginx
  nginx version: nginx/1.19.9
 
-------------------------------------------------------------------------------

Kubernetes Dashboard

Dashboard is an web application which allow inspect and manage cluster services and workloads, after deploy the web application we need setup an service account to allow login later:

kubectl create -f https://raw.githubusercontent.com/rodrigobaron/manifests/main/dashboard/deployment.yaml
kubectl create -f https://raw.githubusercontent.com/rodrigobaron/manifests/main/dashboard/service-account.yaml

To access the Dashboard we have some options, we can either forward the pod ports or expose by the ingress controller. I prefer just expose the service and access through an sub-domain name like:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: k8s-dashboard
  namespace: kubernetes-dashboard
  annotations:
    nginx.ingress.kubernetes.io/backend-protocol: "HTTPS"
    nginx.ingress.kubernetes.io/ssl-passthrough: "true"
    kubernetes.io/ingress.class: nginx
spec:
  tls:
    - hosts:
      - dash.k8s.rodrigobaron.com
      secretName: tls-secret
  rules:
  - host: dash.k8s.rodrigobaron.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: kubernetes-dashboard
            port:
              number: 443

Remember to update your DNS rules or add the entry in your hosts file to point the cluster IP address. For example my /etc/hosts have this entry:

192.168.0.222 k8s.rodrigobaron.com

Finally to access it we need get the authentication token by running:

kubectl -n kube-system describe secret $(kubectl -n kube-system get secret | grep k8s-admin | awk '{print $1}')

Then at end should be able to access in your browser.. eg.: https://dash.k8s.rodrigobaron.com.

Next steps

We completed the basic resource managment, we can create stateful applications, expose them and manage using an web application. Next post we will see about logging and monitoring.

References

• https://kubernetes.io/docs/concepts/services-networking/ingress/ (opens in a new tab)
• https://kubernetes.github.io/ingress-nginx/ (opens in a new tab)
• https://github.com/rancher/local-path-provisioner (opens in a new tab)