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Create a cluster

The Azure CLI automates a large part of what is needed to setup a Kubernetes cluster.

To create a resource group and cluster as described here run;

PS> ./CreateCluster.ps1

NB. This automatically creates a Service Prinpical: https://github.com/MicrosoftDocs/azure-docs/blob/master/articles/aks/kubernetes-service-principal.md

The script creates a cluster with:

  • Linux node (DS2v2, 2 CPUs, 7 GiB RAM, 14 GiB temp storage, €0.1147/hour)
  • Windows node (D2sv3, 2 CPUs, 8 GiB RAM, 16 GiB temp storage, €0.1788/hour) Total costs are approx. €0.30/hour (excluding a small amount of storage costs)

Next, configure kubectl credentials:

PS> az aks get-credentials --resource-group myResourceGroup --name myAKSCluster

Connect to the cluster:

PS> kubectl get nodes

If everything went well you should see 2 nodes.

Browse to the Kubernetes Dashboard to get a visual representation of your cluster:

PS> az aks browse --resource-group myResourceGroup --name myAKSCluster

This introduces the Kubernetes Dashboard.

NB. The dashboard allows to deploy services using the Create App option, but does currently not allow for specifying a nodeSelector. This means that in a multi-os cluster you cannot specify if the container should be deployed on e.g. a Windows or Linux node.

To save some money during development, deallocate the VMs (which are the most costly) in the cluster when you don't use them:

PS> ./StopCluster.ps1

Start the VMs again using:

PS> ./StartCluster.ps1

Setup ACR connection

In order to pull Docker images from an Azure Container Registry you need to grant the cluster Service Principal AcrPull rights.

Get Service Principal Id:

PS> az aks show --resource-group myResourceGroup --name myAKSCluster --query "servicePrincipalProfile.clientId" --output tsv

Use this Id to assign AcrPull rights in the ACR. As the ACR lives under a different subscription its easiest do this using the Azure Portal GUI.

See here for more details.

Add Ingress routing

HTTP application routing using AKS is described here. There are several ways of routing ingress traffic, for HTTP traffic there is a choice of Ingress controllers e.g. Nginx, Traefik. As Nginx seems to be the most commonly used and most well documented for AKS we will use Nginx.

Deploy Nginx Ingress controller

How to deploy a Nginx Ingress controller is described here.

It consists of two steps;

  1. Mandatory part:
PS> kubectl apply -f ./k8s/nginx-ingress.yaml

nginx-ingress.yaml is this + Linux node selector.

  1. A cloud provider specific, Azure part:
PS> kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/provider/cloud-generic.yaml

Add External DNS configuration

By default you will have an IP configured for you cluster. It of course more convenient to have a DNS name assigned to it. As prerequisite you need to have a domain name and Azure DNS zone setup (see here).

To dynamic DNS provisioning for your cluster we use an external-dns service, to set it up;

  • Create a resource group
  • Assign Contributor rights to AKS Cluster Service Principal
  • Create a Kubernetes Secret as described here (Get the aadClientId and aadClientSecret from the automatically created ~/.azure/aksServicePrincipal.json file) Creating a Kubernetes secret basically means uploading a JSON file to Kubernetes, e.g:
PS> kubectl create secret generic azure-config-file --from-file=azure.json

The filename used to create the secret will by default be used as name when the secret is mounted (azure.json in this case)!

Finally deploy the External DNS service:

PS> kubectl apply -f .\k8s\externaldns.yaml

Setup Helm

Helm is a package installer for Kubernetes, it makes application installation much easier.

First install Helm on your host machine:

PS> choco install kubernetes-helm

To install Helm on AKS:

PS> kubectl apply -f ./k8s/helm-rbac.yaml
PS> helm init --service-account tiller --node-selectors "beta.kubernetes.io/os=linux"

Read the full details here.

Add automatic TLS certificates

The preferred way is to use cert-manager. It however currently does not fully support nodeSelector and thus does not work in hybrid cluster, e.g. like we have with a Linux and Windows node.

The legacy way and workaround is to use kube-lego:

PS> helm install kube-lego --set config.LEGO_EMAIL=joost@meijl.es --set config.LEGO_URL=https://acme-v01.api.letsencrypt.org/directory --set nodeSelector."beta\.kubernetes\.io\/os"=linux --set rbac.create=true stable/kube-lego

Next to enable automatic tls generation for a certain ingress route add an annotation;

metadata:
  annotations:
    ...
    kubernetes.io/tls-acme: "true"

to your Ingress spec.

Inspect the logs of the kube-log to follow the certificaton request process, e.g:

PS> kubectl logs kube-lego-kube-lego-7bf7d44dfb-7dnpz

Troubleshooting

Kubernetes Dashboard errors

Multiple permission errors (as mentioned here) show up when browsing the Kubernetes dashboard after performing:

PS> az aks browse --resource-group myResourceGroup --name myAKSCluster

To fix it, run:

PS> kubectl create clusterrolebinding kubernetes-dashboard --clusterrole=cluster-admin --serviceaccount=kube-system:kubernetes-dashboard

Resources after removing Kubernetes cluster

After removing a cluster e.g. using:

PS> az group delete --name myResourceGroup --yes --no-wait

The diagnostics resource group (named DefaultResourceGroup-WEU when using the example) is not removed; remove it manually.

Stop cluster

The VMs inside the cluster cost money. To stop the VMs inside your cluster (i.e. resource group):

az vm deallocate --ids $(az vm list -g <RESOURCE GROUP> --query "[].id" -o tsv)

To start the VMs again:

az vm start --ids $(az vm list -g <RESOURCE GROUP> --query "[].id" -o tsv)

Exec into container

PS> kubectl get pods
PS> kubectl exec -ti <pod name> <cmd>

Service types

Load Balancer vs NodePort vs ClusterIP: https://www.edureka.co/community/19351/clusterip-nodeport-loadbalancer-different-from-each-other

RBAC

Determine if RBAC is enabled for the AKS cluster:

az resource show -g <resource group name> -n <cluster name> --resource-type Microsoft.ContainerService/ManagedClusters --query properties.enableRBAC