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Demo Application

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

Start up the Redis Master

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

  1. Apply the Redis Master Deployment from the redis-master-deployment.yaml file:

    kubectl apply -f https://k8s.io/examples/application/guestbook/redis-master-deployment.yaml

  2. Query the list of Pods to verify that the Redis Master Pod is running:

    kubectl get pods

    The response should be similar to this:

    NAME                            READY     STATUS    RESTARTS   AGE
redis-master-1068406935-3lswp   1/1       Running   0          28s

  3. Run the following command to view the logs from the Redis Master Pod:

    kubectl logs -f POD-NAME

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

Creating the Redis Master Service

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

  1. Apply the Redis Master Service from the following redis-master-service.yaml file:

    kubectl apply -f https://k8s.io/examples/application/guestbook/redis-master-service.yaml

  2. Query the list of Services to verify that the Redis Master Service is running:

    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    46h
redis-master   ClusterIP   10.103.95.1   <none>        6379/TCP   7s

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

Start up the Redis Slaves

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

Creating the Redis Slave 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.

  1. Apply the Redis Slave Deployment from the redis-slave-deployment.yaml file:

    kubectl apply -f https://k8s.io/examples/application/guestbook/redis-slave-deployment.yaml

  2. Query the list of Pods to verify that the Redis Slave Pods are running:

    kubectl get pods

    The response should be similar to this:

    NAME                            READY   STATUS              RESTARTS   AGE
redis-master-6fbbc44567-sxvjh   1/1     Running             0          66s
redis-slave-74ccb764fc-smr7n    0/1     ContainerCreating   0          6s
redis-slave-74ccb764fc-sps4r    0/1     ContainerCreating   0          6s

Creating the Redis Slave Service

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

  1. Apply the Redis Slave Service from the following redis-slave-service.yaml file:

    kubectl apply -f https://k8s.io/examples/application/guestbook/redis-slave-service.yaml

  2. Query the list of Services to verify that the Redis slave service is running:

    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    46h
redis-master   ClusterIP   10.103.95.1      <none>        6379/TCP   2m15s
redis-slave    ClusterIP   10.105.138.125   <none>        6379/TCP   7s

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-master Service for write requests and the redis-slave service for Read requests.

Creating the Guestbook Frontend Deployment

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

    kubectl apply -f https://k8s.io/examples/application/guestbook/frontend-deployment.yaml

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

    kubectl get pods -l app=guestbook -l tier=frontend

    The response should be similar to this:

    NAME                            READY   STATUS    RESTARTS   AGE
frontend-74b4665db5-vr6hf       1/1     Running   0          70s
frontend-74b4665db5-z76vh       1/1     Running   0          70s
frontend-74b4665db5-zg5kw       1/1     Running   0          70s

Creating the Frontend Service

The redis-slave and redis-master 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.

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

    kubectl apply -f https://k8s.io/examples/application/guestbook/frontend-service.yaml

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

    kubectl get services

    The response should be similar to this:

    NAME           TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)        AGE
frontend       NodePort    10.99.225.158    <none>        80:30551/TCP   9s
kubernetes     ClusterIP   10.96.0.1        <none>        443/TCP        46h
redis-master   ClusterIP   10.103.95.1      <none>        6379/TCP       4m17s
redis-slave    ClusterIP   10.105.138.125   <none>        6379/TCP       2m9s

Viewing the Frontend Service via NodePort

Open your browser with address http://kube-node01.kube.local:30551

Keep attention on port 30551, 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.

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

    kubectl scale deployment frontend --replicas=5

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

    kubectl get pods

    The response should look similar to this:

    NAME                            READY   STATUS    RESTARTS   AGE
frontend-74b4665db5-n2bsk       1/1     Running   0          8s
frontend-74b4665db5-sf42s       1/1     Running   0          8s
frontend-74b4665db5-vr6hf       1/1     Running   0          5m24s
frontend-74b4665db5-z76vh       1/1     Running   0          5m24s
frontend-74b4665db5-zg5kw       1/1     Running   0          5m24s
redis-master-6fbbc44567-sxvjh   1/1     Running   0          8m45s
redis-slave-74ccb764fc-smr7n    1/1     Running   0          7m45s
redis-slave-74ccb764fc-sps4r    1/1     Running   0          7m45s

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

    kubectl scale deployment frontend --replicas=2

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

    kubectl get pods

    The response should look similar to this:

    NAME                            READY   STATUS    RESTARTS   AGE
frontend-74b4665db5-z76vh       1/1     Running   0          6m18s
frontend-74b4665db5-zg5kw       1/1     Running   0          6m18s
redis-master-6fbbc44567-sxvjh   1/1     Running   0          9m39s
redis-slave-74ccb764fc-smr7n    1/1     Running   0          8m39s
redis-slave-74ccb764fc-sps4r    1/1     Running   0          8m39s

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.

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

    kubectl delete deployment -l app=redis
kubectl delete service -l app=redis
kubectl delete deployment -l app=guestbook
kubectl delete 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

  2. Query the list of Pods to verify that no Pods are running:

    kubectl get pods

    The response should be this:

    No resources found.