K8s Hands-on 🚢

Here, a random introduction will find its place. Probably I will link the ppt in addition.

This guided hands-on workshop was tested with AKS 1.14.8.

This workshop is accompanied by an instructor and additional slides.

The commands are powershell specific.

Prerequisite

Alternatively you can use http://shell.azure.com

Install docker for windows
Install the Kubernetes command line interface: kubectl
Install Azure CLI
Install the Azure Kubernetes Service command line interface by using the following command

az aks install-cli

Switch to needed Azure subscription

az login

Check which subscriptions are available. Use the --refresh flag since the list is cached.

az account list --refresh

Set the context of the needed subscription. You can either use the name or ID.

az account set --subscription <SUBSCRIPTION>

Create an AKS Cluster

Create a resource group and the AKS cluster. Another resource group will automatically be built during the create process. In the second resource group you will find the infrastructure like virtual machines.

az group create --name <RESOURCEGROUP> --location <LOCATION>

az aks create `
    --resource-group <RESOURCEGROUP> `
    --name <CLUSTERNAME> `
    --node-count 1 `
    --enable-addons monitoring `
    --generate-ssh-keys

Connect to cluster 🔌

You can connect to any azure cluster by downloading the credentials.

az aks get-credentials --resource-group <RESOURCEGROUP> --name <CLUSTERNAME>

To verify if you are successfully connected open the config.

kubectl config get-contexts

Finally, get information about your running nodes.

kubectl get nodes

Kubernetes 101 - the imperative way 🔨

Deploy a cached image

One of the available pre-cached images is an nginx image. Run it with the following command.

Do not worry about the warning that kubeclt run will be deprecated. We want to keep things simple for now and will not use it further.

kubectl run nginx --image=nginx --replicas=3

This command will result in a deployment which is related to a ReplicaSet. The ReplicaSet is responsible for 3 copies of the Pod where the images lives in.

Check if 3 Pods are running.

kubectl get pods

Create a tunnel while using port forwarding. You should see the welcome site of an nginx deployment when you open http//:localhost.

kubectl port-forward <NAME_OF_POD> 80:80

The kubectl run command created a deployment as shown above. Start editing it and analyze the code.

kubectl get deployment

kubectl edit deployment <NAME_OF_DEPLOYMENT>

In the deployment yaml it says replicas: 3. Delete the Pod to see the self-healing mechanism of Kubernetes. To follow the whole process, open another terminal and call kubectl get Pods -w. This will stream any changes.

kubectl delete pod <NAME_OF_POD>

The Pod will be recreated immediately since the ReplicaSet of the deployment says that there should be 3 Pods at any time. This is a huge thing since Kubernetes will always look for the healthiness of your applications.

kubectl get pods

So, if you actually want to delete the three nginx pods you have to delete the deployment. Do that and clean up.

kubectl delete deployment nginx

Kubernetes 101 - the declarative way (YAML) 📓🖊️

In the previous steps you deployed a pre-cached image of nginx with imperative commands. Now you will not be using just yaml to deploy the image in a declarative way but even use your own containerized application. To do so, you must push your application first to a container registry as shown in the picture below. Afterwards you can apply a yaml file directly to the cluster with a link of the image in the container registry.

Create an Azure Container Registry

The Azure Container Registry (ACR) is a private image repository hosted on Azure. Create an ACR by using the azure cli. For simplicity, we set the --admin-enabled flag to true to push an image directly from our command line to the ACR.

az acr create -n <REGISTRY_NAME> -g <RESOURCE_GROUP_NAME> --sku Standard --admin-enabled true --location <LOCATION>

Prepare the Cluster

Next, we will deploy our own images by using yaml files. In these yaml files we will link an ACR. To enable the AKS to access the ACR we can add the privileges to the existing Service Principal (SP) which was created during the cluster creation. In case you do not have enough privileges to do so, we can create a Kubernetes secret. Review this Microsoft Docs to understand both ways.

Replace the variables and run this powershell script to add the privileges to the existing SP.

$AKS_RESOURCE_GROUP="<AKS_RESOURCE_GROUP>"
$AKS_CLUSTER_NAME="<AKS_CLUSTER_NAME>"
$ACR_RESOURCE_GROUP="<ACR_RESOURCE_GROUP>"
$ACR_NAME="ACR_NAME"
$CLIENT_ID=$(az aks show --resource-group $AKS_RESOURCE_GROUP --name $AKS_CLUSTER_NAME --query "servicePrincipalProfile.clientId" --output tsv)
$ACR_ID=$(az acr show --name $ACR_NAME --resource-group $ACR_RESOURCE_GROUP --query "id" --output tsv)
az role assignment create --assignee $CLIENT_ID --role acrpull --scope $ACR_ID

Open the Azure portal and validate if you can see a role assignment from the AKS's SP under Access control of the ACR.

Prepare the sample Node Application 📦

Checkout the js-idrepater which is in this GitHub repository. Run the docker build command. Tag the image with the application's name (js-idrepeater) and set a version number like 1 or v1. Notice that we used the prefix <ACR_NAME>.azurecr.io. We need this prefix for the docker push command later. Do not forget the dot at the end.

docker build -t <ACR_NAME>.azurecr.io/js-idrepeater:1 .

Test js-idrepeater locally. Do not forget to forward the machines port to the container port.

docker run -p 80:80 <ACR_NAME>.azurecr.io/js-idrepeater:1

To validate that the application is running, open a browser and call the localhost. You will see a random four-digit key. This key is generated on startup of the container and will not change during the whole lifecycle of the container. To understand this behavior, kill the container and run it once again.

http://localhost:80

As we confirmed that the container is running we will push our image to our newly created ACR. First authenticate with the ACR.

az acr login -n <ACR_NAME>

docker push <ACR_NAME>.azurecr.io/js-idrepeater:1

Visit the ACR resource in the Azure portal to verify the upload. Look for Repositories in the menu and check if a repository with js-idrepeater was created.

Deploy the `js-idrepeater` to your AKS Cluster 🚀

Next you will create a Kubernetes deployment yaml. In the source tree of js-idrepeater create a folder named manifests. Inside, create a file and call it deployment.yml. If you stick to the provided names of the folder and files Azure DevOps can read these files automatically in a later exercise of this workshop.

Please consider, that you have to point to the correct version of your image! For now you are good by taking 1. Since we applied the privileges to access the ACR to the SP we are all good. If you had to create a Kubernetes secret before please use it now as an imagePullSecrets. Place it like this spec.template.spec.imagePullSecrets.

apiVersion : apps/v1beta1
kind: Deployment
metadata:
  name: js-idrepeater 
spec:
  replicas: 2
  template:
    metadata:
      labels:
        app: js-idrepeater
    spec:
      containers:
        - name: js-idrepeater 
          image: <ACR_NAME>.azurecr.io/js-idrepeater:1
          ports:
          - containerPort: 80

As we did not specify any namespace, the default namespace is used

Next, apply the Deployment to your Kubernetes cluster.

kubectl apply -f .\deployment.yml

Check if the deployment created your Pod.

kubectl get pods

Forward to this Pod and call http://localhost.

kubectl port-forward <NAME_OF_Pod> 80:80

Self testing 💉

The cluster will immediately recreate a Pod if a container / Pod crashes. But that way you do not validate if the application inside the container is still running. Therefore, you can specify in any deployment yaml a liveness probe. The following liveness probe is calling the API healthz with a initial delay of three seconds.

The node application will spin up in three seconds. But always consider that some applications will take longer.

livenessProbe:
  httpGet:
    path: /healthz
    port: 80
  initialDelaySeconds: 3
  periodSeconds: 3

The full deployment yaml will look like the following. Use kubectl apply -f <FILENAME> to deploy it.

apiVersion : apps/v1beta1
kind: Deployment
metadata:
  name: js-idrepeater 
spec:
  replicas: 2
  template:
    metadata:
      labels:
        app: js-idrepeater
    spec:
      containers:
        - name: js-idrepeater 
          image: <ACR_NAME>.azurecr.io/js-idrepeater:1
          ports:
          - containerPort: 80
          livenessProbe:
              httpGet:
                path: /healthz
                port: 80
              initialDelaySeconds: 3
              periodSeconds: 3

Kubernetes' Service discovery 🔎

As you already noticed there are more than just one js-idrepeater Pod. You need an abstraction layer which knows every Pod no matter on which node it is running on. Other scenarios can be scale-out, recreation of a Pod, scheduling Pods to other nodes and all other cases in which Pods might change their IP or count. The Service is doing this job in Kubernetes. The Service uses selectors which matches with labels in the Pod yaml.

Inspect the deployment.yaml file and find the spec.template.metadata.labels.app which is set to js-idrepeater.

Create the file Service.yml next to the deployment file. Then apply it to your AKS.

apiVersion: v1
kind: Service
metadata:
   name: js-idrepeater
spec:
   ports:
   - port: 80 
   selector:
       app: js-idrepeater

kubectl apply -f .\service.yml

Now, all Pods of js-idrepeater are reachable through the Service. Check if the Service is running.

kubectl get svc

Next, log on one of the running Pods and call the another one by using the Service.

kubectl get pods

kubectl exec -it <POD_NAME_NGINX> /bin/sh

wget http://js-idrepeater

cat index.html

Exposing the Service to the outside by assigning a LoadBalancer with IP

Edit the yaml of the Service as follows. By default, the type of a Service is ClusterIp and it is not needed to specify. We will change it to LoadBalancer. When you update the Service with the new yaml file Kubernetes will use the SP to create a IP and LoadBalancer. Afterwards a rule will be automatically defined which routes the traffic to the IP directly to the Service in the AKS.

apiVersion: v1
kind: Service
metadata:
   name: js-idrepeater
spec:
   ports:
   - port: 80 
   selector:
       app: js-idrepeater
   type: LoadBalancer

kubectl apply -f .\service.yml

It will take some time until the IP is scheduled.

kubectl get svc -w

Configure an Ingress 🛰️

Kubernetes is supporting the concept of an Ingress. In the following we will use the standard nginx Ingress but there are a lot of open source projects which offers much more value than just a reverse proxy. You will use helm to install the nginx.

Install helm

Helm is a package manager and can keep track of your deployments to e.g. roll back. Go to the release page and install helm.

https://github.com/helm/helm/releases

Next, add the repository with the stable releases of public helm charts.

helm repo add stable https://kubernetes-charts.storage.googleapis.com/

You may encounter the concept of helm client and tiller, where tiller is the 'server-side' part of helm which handels the deployments in the K8s cluster. This is deprecated since helm version 3.

Setup an Ingress which works with basic http.

For simplicity we will use a basic http configured nginx. Please consider to use TLS secured nginx deployments.

The Ingress will be our reverse proxy.

helm install stable/nginx-ingress `
    --set controller.replicaCount=1 `
    --set controller.nodeSelector."beta\.kubernetes\.io/os"=linux `
    --set defaultBackend.nodeSelector."beta\.kubernetes\.io/os"=linux

The command helm ls will show you all installed helm repositories.

helm ls

Check the running Pods und Services.

kubectl get pods

kubectl get svc

The exposed Service of the nginx will show a 404 error since we just installed the nginx but did not tell where to route the traffic. To solve this we have to create an Ingress route which points to our Service of js-idrepeater.

apiVersion: extensions/v1beta1
kind: Ingress
metadata:
  name: ingress-js-idrepeater
  annotations:
    kubernetes.io/ingress.class: nginx
    nginx.ingress.kubernetes.io/ssl-redirect: "false"
    nginx.ingress.kubernetes.io/rewrite-target: /$2
spec:
  rules:
  - http:
      paths:
      - backend:
          serviceName: js-idrepeater
          servicePort: 80
        path: /js-idrepeater

Apply this ingress route to your cluster.

kubectl apply -f .\ingress.yml

Reopen the website. You find the IP by calling kubectl get svc.

sebastianspross/k8s101