Example: Deploying PHP Guestbook application with Redis


This tutorial shows you how to build and deploy a simple (not production ready), multi-tier web application using Kubernetes and Docker. This example consists of the following components:

  • A single-instance Redis to store guestbook entries
  • Multiple web frontend instances

Objectives

  • Start up a Redis leader.
  • Start up two Redis followers.
  • Start up the guestbook frontend.
  • Expose and view the Frontend Service.
  • Clean up.

Before you begin

You need to have a Kubernetes cluster, and the kubectl command-line tool must be configured to communicate with your cluster. It is recommended to run this tutorial on a cluster with at least two nodes that are not acting as control plane hosts. If you do not already have a cluster, you can create one by using minikube or you can use one of these Kubernetes playgrounds:

Your Kubernetes server must be at or later than version v1.14. To check the version, enterkubectl version.

Start up the Redis Database

The guestbook application uses Redis to store its data.

Creating the Redis Deployment

The manifest file, included below, specifies a Deployment controller that runs a single replica Redis Pod.

application/guestbook/redis-leader-deployment.yaml # SOURCE: https://cloud.google.com/kubernetes-engine/docs/tutorials/guestbook apiVersion: apps/v1 kind: Deployment metadata: name: redis-leader labels: app: redis role: leader tier: backend spec: replicas: 1 selector: matchLabels: app: redis template: metadata: labels: app: redis role: leader tier: backend spec: containers: – name: leader image: “docker.io/redis:6.0.5” resources: requests: cpu: 100m memory: 100Mi ports: – containerPort: 6379

  1. Launch a terminal window in the directory you downloaded the manifest files.

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

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

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

    kubectl get pods

    The response should be similar to this:

    NAME READY STATUS RESTARTS AGE redis-leader-fb76b4755-xjr2n 1/1 Running 0 13s

  4. Run the following command to view the logs from the Redis leader Pod:

    kubectl logs -f deployment/redis-leader

Creating the Redis leader Service

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

application/guestbook/redis-leader-service.yaml # SOURCE: https://cloud.google.com/kubernetes-engine/docs/tutorials/guestbook apiVersion: v1 kind: Service metadata: name: redis-leader labels: app: redis role: leader tier: backend spec: ports: – port: 6379 targetPort: 6379 selector: app: redis role: leader tier: backend

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

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

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

    kubectl get service

    The response should be similar to this:

    NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.0.0.1 443/TCP 1m redis-leader ClusterIP 10.103.78.24 6379/TCP 16s

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

Set up Redis followers

Although the Redis leader is a single Pod, you can make it highly available and meet traffic demands by adding a few Redis followers, or replicas.

application/guestbook/redis-follower-deployment.yaml # SOURCE: https://cloud.google.com/kubernetes-engine/docs/tutorials/guestbook apiVersion: apps/v1 kind: Deployment metadata: name: redis-follower labels: app: redis role: follower tier: backend spec: replicas: 2 selector: matchLabels: app: redis template: metadata: labels: app: redis role: follower tier: backend spec: containers: – name: follower image: gcr.io/google_samples/gb-redis-follower:v2 resources: requests: cpu: 100m memory: 100Mi ports: – containerPort: 6379

  1. Apply the Redis Service from the following redis-follower-deployment.yaml file:

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

  2. Verify that the two Redis follower replicas are running by querying the list of Pods:

    kubectl get pods

    The response should be similar to this:

    NAME READY STATUS RESTARTS AGE redis-follower-dddfbdcc9-82sfr 1/1 Running 0 37s redis-follower-dddfbdcc9-qrt5k 1/1 Running 0 38s redis-leader-fb76b4755-xjr2n 1/1 Running 0 11m

Creating the Redis follower service

The guestbook application needs to communicate with the Redis followers to read data. To make the Redis followers discoverable, you must set up another Service.

application/guestbook/redis-follower-service.yaml # SOURCE: https://cloud.google.com/kubernetes-engine/docs/tutorials/guestbook apiVersion: v1 kind: Service metadata: name: redis-follower labels: app: redis role: follower tier: backend spec: ports: # the port that this service should serve on – port: 6379 selector: app: redis role: follower tier: backend

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

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

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

    kubectl get service

    The response should be similar to this:

    NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.96.0.1 443/TCP 3d19h redis-follower ClusterIP 10.110.162.42 6379/TCP 9s redis-leader ClusterIP 10.103.78.24 6379/TCP 6m10s

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

Set up and Expose the Guestbook Frontend

Now that you have the Redis storage of your guestbook up and running, start the guestbook web servers. Like the Redis followers, the frontend is deployed using a Kubernetes Deployment.

The guestbook app uses a PHP frontend. It is configured to communicate with either the Redis follower or leader Services, depending on whether the request is a read or a write. The frontend exposes a JSON interface, and serves a jQuery-Ajax-based UX.

Creating the Guestbook Frontend Deployment

application/guestbook/frontend-deployment.yaml # SOURCE: https://cloud.google.com/kubernetes-engine/docs/tutorials/guestbook apiVersion: apps/v1 kind: Deployment metadata: name: frontend spec: replicas: 3 selector: matchLabels: app: guestbook tier: frontend template: metadata: labels: app: guestbook tier: frontend spec: containers: – name: php-redis image: gcr.io/google_samples/gb-frontend:v5 env: – name: GET_HOSTS_FROM value: “dns” resources: requests: cpu: 100m memory: 100Mi ports: – containerPort: 80

  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-85595f5bf9-5tqhb 1/1 Running 0 47s frontend-85595f5bf9-qbzwm 1/1 Running 0 47s frontend-85595f5bf9-zchwc 1/1 Running 0 47s

Creating the Frontend Service

The Redis Services you applied is only accessible within the Kubernetes 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.

If you want guests to be able to access your guestbook, you must configure the frontend Service to be externally visible, so a client can request the Service from outside the Kubernetes cluster. However a Kubernetes user you can use kubectl port-forward to access the service even though it uses a ClusterIP.

Note:Some cloud providers, like Google Compute Engine or Google Kubernetes Engine, support external load balancers. If your cloud provider supports load balancers and you want to use it, uncommenttype: LoadBalancer.

application/guestbook/frontend-service.yaml # SOURCE: https://cloud.google.com/kubernetes-engine/docs/tutorials/guestbook apiVersion: v1 kind: Service metadata: name: frontend labels: app: guestbook tier: frontend spec: # if your cluster supports it, uncomment the following to automatically create # an external load-balanced IP for the frontend service. # type: LoadBalancer #type: LoadBalancer ports: # the port that this service should serve on – port: 80 selector: app: guestbook tier: frontend

  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 ClusterIP 10.97.28.230 80/TCP 19s kubernetes ClusterIP 10.96.0.1 443/TCP 3d19h redis-follower ClusterIP 10.110.162.42 6379/TCP 5m48s redis-leader ClusterIP 10.103.78.24 6379/TCP 11m

Viewing the Frontend Service via kubectl port-forward

  1. Run the following command to forward port 8080 on your local machine to port 80 on the service.

    kubectl port-forward svc/frontend 8080:80

    The response should be similar to this:

    Forwarding from 127.0.0.1:8080 -> 80 Forwarding from [::1]:8080 -> 80

  2. load the page http://localhost:8080 in your browser to view your guestbook.

Viewing the Frontend Service via LoadBalancer

If you deployed the frontend-service.yaml manifest with type: LoadBalancer you need to find the IP address to view your Guestbook.

  1. Run the following command to get the IP address for the frontend Service.

    kubectl get service frontend

    The response should be similar to this:

    NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE frontend LoadBalancer 10.51.242.136 109.197.92.229 80:32372/TCP 1m

  2. Copy the external IP address, and load the page in your browser to view your guestbook.

Note: Try adding some guestbook entries by typing in a message, and clicking Submit. The message you typed appears in the frontend. This message indicates that data is successfully added to Redis through the Services you created earlier.

Scale the Web Frontend

You can scale up or down as needed 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-85595f5bf9-5df5m 1/1 Running 0 83s frontend-85595f5bf9-7zmg5 1/1 Running 0 83s frontend-85595f5bf9-cpskg 1/1 Running 0 15m frontend-85595f5bf9-l2l54 1/1 Running 0 14m frontend-85595f5bf9-l9c8z 1/1 Running 0 14m redis-follower-dddfbdcc9-82sfr 1/1 Running 0 97m redis-follower-dddfbdcc9-qrt5k 1/1 Running 0 97m redis-leader-fb76b4755-xjr2n 1/1 Running 0 108m

  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-85595f5bf9-cpskg 1/1 Running 0 16m frontend-85595f5bf9-l9c8z 1/1 Running 0 15m redis-follower-dddfbdcc9-82sfr 1/1 Running 0 98m redis-follower-dddfbdcc9-qrt5k 1/1 Running 0 98m redis-leader-fb76b4755-xjr2n 1/1 Running 0 109m

Cleaning up

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 frontend kubectl delete service frontend

    The response should look similar to this:

    deployment.apps “redis-follower” deleted deployment.apps “redis-leader” 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 look similar to this:

    No resources found in default namespace.

What’s next

Last modified June 17, 2021 at 4:45 AM PST : updating tutorial to match source (ff0018b97)

Source

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