--- title: "Example: Deploying PHP Guestbook application with Redis" reviewers: - ahmetb content_type: tutorial weight: 20 card: name: tutorials weight: 30 title: "Stateless Example: PHP Guestbook with Redis" --- This tutorial shows you how to build and deploy a simple, multi-tier web application using Kubernetes and [Docker](https://www.docker.com/). This example consists of the following components: * A single-instance [Redis](https://redis.io/) master to store guestbook entries * Multiple [replicated Redis](https://redis.io/topics/replication) instances to serve reads * Multiple web frontend instances ## {{% heading "objectives" %}} * Start up a Redis master. * Start up Redis slaves. * Start up the guestbook frontend. * Expose and view the Frontend Service. * Clean up. ## {{% heading "prerequisites" %}} {{< include "task-tutorial-prereqs.md" >}} {{< version-check >}} ## 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. ### Creating the Redis Master Deployment The manifest file, included below, specifies a Deployment controller that runs a single replica Redis master Pod. {{< codenew file="application/guestbook/redis-master-deployment.yaml" >}} 1. Launch a terminal window in the directory you downloaded the manifest files. 1. Apply the Redis Master Deployment from the `redis-master-deployment.yaml` file: ```shell kubectl apply -f https://k8s.io/examples/application/guestbook/redis-master-deployment.yaml ``` 1. Query the list of Pods to verify that the Redis Master Pod is running: ```shell kubectl get pods ``` The response should be similar to this: ```shell NAME READY STATUS RESTARTS AGE redis-master-1068406935-3lswp 1/1 Running 0 28s ``` 1. Run the following command to view the logs from the Redis Master Pod: ```shell kubectl logs -f POD-NAME ``` {{< note >}} Replace POD-NAME with the name of your Pod. {{< /note >}} ### Creating the Redis Master Service The guestbook application needs to communicate to the Redis master to write its data. You need to apply a [Service](/docs/concepts/services-networking/service/) to proxy the traffic to the Redis master Pod. A Service defines a policy to access the Pods. {{< codenew file="application/guestbook/redis-master-service.yaml" >}} 1. Apply the Redis Master Service from the following `redis-master-service.yaml` file: ```shell kubectl apply -f https://k8s.io/examples/application/guestbook/redis-master-service.yaml ``` 1. Query the list of Services to verify that the Redis Master Service is running: ```shell kubectl get service ``` The response should be similar to this: ```shell NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.0.0.1 443/TCP 1m redis-master ClusterIP 10.0.0.151 6379/TCP 8s ``` {{< 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. {{< /note >}} ## 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 running, it would scale down until two replicas are running. {{< codenew file="application/guestbook/redis-slave-deployment.yaml" >}} 1. Apply the Redis Slave Deployment from the `redis-slave-deployment.yaml` file: ```shell kubectl apply -f https://k8s.io/examples/application/guestbook/redis-slave-deployment.yaml ``` 1. Query the list of Pods to verify that the Redis Slave Pods are running: ```shell kubectl get pods ``` The response should be similar to this: ```shell NAME READY STATUS RESTARTS AGE redis-master-1068406935-3lswp 1/1 Running 0 1m redis-slave-2005841000-fpvqc 0/1 ContainerCreating 0 6s redis-slave-2005841000-phfv9 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. {{< codenew file="application/guestbook/redis-slave-service.yaml" >}} 1. Apply the Redis Slave Service from the following `redis-slave-service.yaml` file: ```shell kubectl apply -f https://k8s.io/examples/application/guestbook/redis-slave-service.yaml ``` 1. Query the list of Services to verify that the Redis slave service is running: ```shell kubectl get services ``` The response should be similar to this: ``` NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE kubernetes ClusterIP 10.0.0.1 443/TCP 2m redis-master ClusterIP 10.0.0.151 6379/TCP 1m redis-slave ClusterIP 10.0.0.223 6379/TCP 6s ``` ## 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 {{< codenew file="application/guestbook/frontend-deployment.yaml" >}} 1. Apply the frontend Deployment from the `frontend-deployment.yaml` file: ```shell kubectl apply -f https://k8s.io/examples/application/guestbook/frontend-deployment.yaml ``` 1. Query the list of Pods to verify that the three frontend replicas are running: ```shell kubectl get pods -l app=guestbook -l tier=frontend ``` The response should be similar to this: ``` NAME READY STATUS RESTARTS AGE frontend-3823415956-dsvc5 1/1 Running 0 54s frontend-3823415956-k22zn 1/1 Running 0 54s frontend-3823415956-w9gbt 1/1 Running 0 54s ``` ### 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](/docs/concepts/services-networking/service/#publishing-services---service-types). `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 container cluster. Minikube can only expose Services through `NodePort`. {{< 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, simply delete or comment out `type: NodePort`, and uncomment `type: LoadBalancer`. {{< /note >}} {{< codenew file="application/guestbook/frontend-service.yaml" >}} 1. Apply the frontend Service from the `frontend-service.yaml` file: ```shell kubectl apply -f https://k8s.io/examples/application/guestbook/frontend-service.yaml ``` 1. Query the list of Services to verify that the frontend Service is running: ```shell kubectl get services ``` The response should be similar to this: ``` NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE frontend NodePort 10.0.0.112 80:31323/TCP 6s kubernetes ClusterIP 10.0.0.1 443/TCP 4m redis-master ClusterIP 10.0.0.151 6379/TCP 2m redis-slave ClusterIP 10.0.0.223 6379/TCP 1m ``` ### Viewing the Frontend Service via `NodePort` If you deployed this application to Minikube or a local cluster, 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. ```shell minikube service frontend --url ``` The response should be similar to this: ``` http://192.168.99.100:31323 ``` 1. Copy the IP address, and load the page 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. ```shell kubectl get service frontend ``` The response should be similar to this: ``` NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE frontend ClusterIP 10.51.242.136 109.197.92.229 80:32372/TCP 1m ``` 1. Copy the external IP address, and load the page in your browser to view your guestbook. ## 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: ```shell kubectl scale deployment frontend --replicas=5 ``` 1. Query the list of Pods to verify the number of frontend Pods running: ```shell kubectl get pods ``` The response should look similar to this: ``` NAME READY STATUS RESTARTS AGE frontend-3823415956-70qj5 1/1 Running 0 5s frontend-3823415956-dsvc5 1/1 Running 0 54m frontend-3823415956-k22zn 1/1 Running 0 54m frontend-3823415956-w9gbt 1/1 Running 0 54m frontend-3823415956-x2pld 1/1 Running 0 5s redis-master-1068406935-3lswp 1/1 Running 0 56m redis-slave-2005841000-fpvqc 1/1 Running 0 55m redis-slave-2005841000-phfv9 1/1 Running 0 55m ``` 1. Run the following command to scale down the number of frontend Pods: ```shell kubectl scale deployment frontend --replicas=2 ``` 1. Query the list of Pods to verify the number of frontend Pods running: ```shell kubectl get pods ``` The response should look similar to this: ``` NAME READY STATUS RESTARTS AGE frontend-3823415956-k22zn 1/1 Running 0 1h frontend-3823415956-w9gbt 1/1 Running 0 1h redis-master-1068406935-3lswp 1/1 Running 0 1h redis-slave-2005841000-fpvqc 1/1 Running 0 1h redis-slave-2005841000-phfv9 1/1 Running 0 1h ``` ## {{% heading "cleanup" %}} 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. ```shell 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 ``` 1. Query the list of Pods to verify that no Pods are running: ```shell kubectl get pods ``` The response should be this: ``` No resources found. ``` ## {{% heading "whatsnext" %}} * Add [ELK logging and monitoring](/docs/tutorials/stateless-application/guestbook-logs-metrics-with-elk/) to your Guestbook application * Complete the [Kubernetes Basics](/docs/tutorials/kubernetes-basics/) Interactive Tutorials * Use Kubernetes to create a blog using [Persistent Volumes for MySQL and Wordpress](/docs/tutorials/stateful-application/mysql-wordpress-persistent-volume/#visit-your-new-wordpress-blog) * Read more about [connecting applications](/docs/concepts/services-networking/connect-applications-service/) * Read more about [Managing Resources](/docs/concepts/cluster-administration/manage-deployment/#using-labels-effectively)