Demo Application

Full referenced: https://kubernetes.io/docs/tutorials/stateless-application/guestbook/

Configure your local routing

You need to add a route to your local machine to access the internal network of Virtualbox.

~$ sudo ip route add 192.168.4.0/27 via 192.168.4.30 dev vboxnet0
~$ sudo ip route add 192.168.4.32/27 via 192.168.4.62 dev vboxnet0
~$ sudo ip route add 192.168.2.0/24 via 192.168.4.254 dev vboxnet0

Access the BusyBox

We need to get the BusyBox IP to access it via ssh

~$ vboxmanage guestproperty get busybox "/VirtualBox/GuestInfo/Net/0/V4/IP"

Expected output:

Value: 192.168.4.57

Use the returned value to access.

~$ ssh debian@192.168.4.57

Start up the Redis Leader

The guestbook application uses Redis to store its data. It writes its data to a Redis leader instance and reads data from multiple Redis followers instances.

Apply the Redis Leader Deployment from the redis-leader-deployment.yaml file:

debian@busybox:~$ kubectl apply -f https://k8s.io/examples/application/guestbook/redis-leader-deployment.yaml

Query the list of Pods to verify that the Redis Leader Pod is running:

debian@busybox:~$ kubectl get pods

The response should be similar to this:

NAME                           READY   STATUS    RESTARTS   AGE
redis-leader-fb76b4755-g7s42   1/1     Running   0          11s

Run the following command to view the logs from the Redis Leader Pod:
```
kubectl logs -f POD-NAME
```

Note: Replace POD-NAME with the name of your Pod.

Creating the Redis Leader Service

The guestbook applications needs to communicate to the Redis leader to write its data. You need to apply a Service to proxy the traffic to the Redis leader Pod. A Service defines a policy to access the Pods.

Apply the Redis Leader Service from the following redis-leader-service.yaml file:

debian@busybox:~$ kubectl apply -f https://k8s.io/examples/application/guestbook/redis-leader-service.yaml

Query the list of Services to verify that the Redis Leader Service is running:

debian@busybox:~$ kubectl get service

The response should be similar to this:

NAME           TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
kubernetes     ClusterIP   10.96.0.1        <none>        443/TCP    2d22h
redis-leader   ClusterIP   10.101.140.177   <none>        6379/TCP   5s

Note: This manifest file creates a Service named redis-leader with a set of labels that match the labels previously defined, so the Service routes network traffic to the Redis leader Pod.

Start up the Redis Followers

Although the Redis leader is a single pod, you can make it highly available to meet traffic demands by adding replica Redis followers.

Creating the Redis Follower Deployment

Deployments scale based off of the configurations set in the manifest file. In this case, the Deployment object specifies two replicas.

If there are not any replicas running, this Deployment would start the two replicas on your container cluster. Conversely, if there are more than two replicas are running, it would scale down until two replicas are running.

Apply the Redis Follower Deployment from the redis-follower-deployment.yaml file:

debian@busybox:~$ kubectl apply -f https://k8s.io/examples/application/guestbook/redis-follower-deployment.yaml

Query the list of Pods to verify that the Redis Follower Pods are running:

debian@busybox:~$ kubectl get pods

The response should be similar to this:

NAME                             READY   STATUS    RESTARTS   AGE
redis-follower-dddfbdcc9-4pcrs   1/1     Running   0          18s
redis-follower-dddfbdcc9-jfs29   1/1     Running   0          18s
redis-leader-fb76b4755-g7s42     1/1     Running   0          4m36s

Creating the Redis Replica Service

The guestbook application needs to communicate to Redis followers to read data. To make the Redis followers discoverable, you need to set up a Service. A Service provides transparent load balancing to a set of Pods.

Apply the Redis Follower Service from the following redis-follower-service.yaml file:

debian@busybox:~$ kubectl apply -f https://k8s.io/examples/application/guestbook/redis-follower-service.yaml

Query the list of Services to verify that the Redis follower service is running:

debian@busybox:~$ kubectl get services

The response should be similar to this:

NAME             TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)    AGE
kubernetes       ClusterIP   10.96.0.1        <none>        443/TCP    2d22h
redis-follower   ClusterIP   10.98.90.120     <none>        6379/TCP   8s
redis-leader     ClusterIP   10.101.140.177   <none>        6379/TCP   4m24s

Set up and Expose the Guestbook Frontend

The guestbook application has a web frontend serving the HTTP requests written in PHP. It is configured to connect to the redis-leader Service for write requests and the redis-follower service for Read requests.

Creating the Guestbook Frontend Deployment

Apply the frontend Deployment from the frontend-deployment.yaml file:

debian@busybox:~$ kubectl apply -f https://k8s.io/examples/application/guestbook/frontend-deployment.yaml

Query the list of Pods to verify that the three frontend replicas are running:

debian@busybox:~$ kubectl get pods -l app=guestbook -l tier=frontend

The response should be similar to this:

NAME                        READY   STATUS    RESTARTS   AGE
frontend-85595f5bf9-cdlkc   1/1     Running   0          71s
frontend-85595f5bf9-d7p9m   1/1     Running   0          71s
frontend-85595f5bf9-mpvhz   1/1     Running   0          71s

Creating the Frontend Service

The redis-follower and redis-leader Services you applied are only accessible within the container cluster because the default type for a Service is ClusterIP. ClusterIP provides a single IP address for the set of Pods the Service is pointing to. This IP address is accessible only within the cluster.

Apply the frontend Service from the frontend-service.yaml file:

debian@busybox:~$ kubectl apply -f https://raw.githubusercontent.com/mvallim/kubernetes-under-the-hood/master/services/kube-service-nodeport.yaml

Query the list of Services to verify that the frontend Service is running:

debian@busybox:~$ kubectl get services

The response should be similar to this:

NAME               TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
kubernetes         ClusterIP   10.96.0.1        <none>        443/TCP        2d22h
nodeport-service   NodePort    10.105.255.221   <none>        80:32767/TCP   12s
redis-follower     ClusterIP   10.98.90.120     <none>        6379/TCP       11m
redis-leader       ClusterIP   10.101.140.177   <none>        6379/TCP       15m

Viewing the Frontend Service via `NodePort`

Query the nodes and ip information

debian@busybox:~$ kubectl get nodes -o wide

The response should look similar to this:

NAME          STATUS   ROLES                  AGE     VERSION    INTERNAL-IP     EXTERNAL-IP   OS-IMAGE                       KERNEL-VERSION    CONTAINER-RUNTIME
kube-mast01   Ready    control-plane,master   2d22h   v1.20.15   192.168.1.18    <none>        Debian GNU/Linux 10 (buster)   4.19.0-18-amd64   containerd://1.4.12
kube-mast02   Ready    control-plane,master   2d22h   v1.20.15   192.168.1.27    <none>        Debian GNU/Linux 10 (buster)   4.19.0-18-amd64   containerd://1.4.12
kube-mast03   Ready    control-plane,master   2d22h   v1.20.15   192.168.1.37    <none>        Debian GNU/Linux 10 (buster)   4.19.0-18-amd64   containerd://1.4.12
kube-node01   Ready    <none>                 2d22h   v1.20.15   192.168.2.185   <none>        Debian GNU/Linux 10 (buster)   4.19.0-18-amd64   containerd://1.4.12
kube-node02   Ready    <none>                 2d22h   v1.20.15   192.168.2.159   <none>        Debian GNU/Linux 10 (buster)   4.19.0-18-amd64   containerd://1.4.12
kube-node03   Ready    <none>                 2d22h   v1.20.15   192.168.2.171   <none>        Debian GNU/Linux 10 (buster)   4.19.0-18-amd64   containerd://1.4.12

Choice any ip of kube-nodes (kube-node01, kube-node02 or kube-node03)

Here we will use the 192.168.2.185 (kube-node01)

Open your browser with address http://192.168.2.185:32767

Keep attention on port 32767, you should change correspondent port show in your on output above.

Scale the Web Frontend

Scaling up or down is easy because your servers are defined as a Service that uses a Deployment controller.

Run the following command to scale up the number of frontend Pods:

debian@busybox:~$ kubectl scale deployment frontend --replicas=5

Query the list of Pods to verify the number of frontend Pods running:

debian@busybox:~$ kubectl get pods

The response should look similar to this:

NAME                             READY   STATUS    RESTARTS   AGE
frontend-85595f5bf9-cdlkc        1/1     Running   0          12m
frontend-85595f5bf9-d7p9m        1/1     Running   0          12m
frontend-85595f5bf9-lvpfh        1/1     Running   0          6s
frontend-85595f5bf9-mpvhz        1/1     Running   0          12m
frontend-85595f5bf9-srn4q        1/1     Running   0          6s
redis-follower-dddfbdcc9-4pcrs   1/1     Running   0          15m
redis-follower-dddfbdcc9-jfs29   1/1     Running   0          15m
redis-leader-fb76b4755-g7s42     1/1     Running   0          20m

Run the following command to scale down the number of frontend Pods:

debian@busybox:~$ kubectl scale deployment frontend --replicas=2

Query the list of Pods to verify the number of frontend Pods running:

debian@busybox:~$ kubectl get pods

The response should look similar to this:

NAME                             READY   STATUS    RESTARTS   AGE
frontend-85595f5bf9-cdlkc        1/1     Running   0          13m
frontend-85595f5bf9-d7p9m        1/1     Running   0          13m
redis-follower-dddfbdcc9-4pcrs   1/1     Running   0          16m
redis-follower-dddfbdcc9-jfs29   1/1     Running   0          16m
redis-leader-fb76b4755-g7s42     1/1     Running   0          20m

Cleaning up (Don’t clean if you enable `LoadBalancer`)

Deleting the Deployments and Services also deletes any running Pods. Use labels to delete multiple resources with one command.

Run the following commands to delete all Pods, Deployments, and Services.

debian@busybox:~$ kubectl delete -n default deployment frontend

debian@busybox:~$ kubectl delete -n default deployment redis-follower

debian@busybox:~$ kubectl delete -n default deployment redis-leader

debian@busybox:~$ kubectl delete -n default service -l app=redis

debian@busybox:~$ kubectl delete -n default service -l app=guestbook

The responses should be:

deployment.apps "redis-master" deleted
deployment.apps "redis-slave" deleted
service "redis-master" deleted
service "redis-slave" deleted
deployment.apps "frontend" deleted
service "frontend" deleted

Query the list of Pods to verify that no Pods are running:
```
debian@busybox:~$ kubectl get pods
```
The response should be this:
```
No resources found in default namespace.
```

Demo Application

Configure your local routing

Access the BusyBox

Start up the Redis Leader

Creating the Redis Leader Service

Start up the Redis Followers

Creating the Redis Follower Deployment

Creating the Redis Replica Service

Set up and Expose the Guestbook Frontend

Creating the Guestbook Frontend Deployment

Creating the Frontend Service

Viewing the Frontend Service via NodePort

Scale the Web Frontend

Cleaning up (Don’t clean if you enable LoadBalancer)

Viewing the Frontend Service via `NodePort`

Cleaning up (Don’t clean if you enable `LoadBalancer`)