Running and Exposing PHP-Apache Server & Starting Horizontal Pod Autoscaler

Let’s see our cluster, it should have two nodes: ``` $ kubectl get nodes NAME STATUS AGE kubernetes-master Ready,SchedulingDisabled 2m kubernetes-minion-group-de5q Ready 2m kubernetes-minion-group-yhdx Ready 1m ``` #### Run & Expose PHP-Apache Server To demonstrate autoscaling we will use a custom docker image based on php-apache server. The image can be found [here](https://github.com/kubernetes/kubernetes/blob/8caeec429ee1d2a9df7b7a41b21c626346b456fb/docs/user-guide/horizontal-pod-autoscaling/image). It defines [index.php](https://github.com/kubernetes/kubernetes/blob/8caeec429ee1d2a9df7b7a41b21c626346b456fb/docs/user-guide/horizontal-pod-autoscaling/image/index.php) page which performs some CPU intensive computations. First, we’ll start a deployment running the image and expose it as a service: ``` $ kubectl run php-apache \ --image=gcr.io/google\_containers/hpa-example \ --requests=cpu=500m,memory=500M --expose --port=80 service "php-apache" createddeployment "php-apache" created ``` Now, we will wait some time and verify that both the deployment and the service were correctly created and are running: ``` $ kubectl get deployment NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE php-apache 1 1 1 1 49s $ kubectl get pods NAME READY STATUS RESTARTS AGE php-apache-2046965998-z65jn 1/1 Running 0 30s ``` We may now check that php-apache server works correctly by calling wget with the service's address: ``` $ kubectl run -i --tty service-test --image=busybox /bin/sh Hit enter for command prompt $ wget -q -O- http://php-apache.default.svc.cluster.local OK! ``` #### Starting Horizontal Pod Autoscaler Now that the deployment is running, we will create a Horizontal Pod Autoscaler for it. To create it, we will use kubectl autoscale command, which looks like this: ``` $ kubectl autoscale deployment php-apache --cpu-percent=50 --min=1 --max=10 ``` This defines a Horizontal Ppod Autoscaler that maintains between 1 and 10 replicas of the Pods controlled by the php-apache deployment we created in the first step of these instructions. Roughly speaking, the horizontal autoscaler will increase and decrease the number of replicas (via the deployment) so as to maintain an average CPU utilization across all Pods of 50% (since each pod requests 500 milli-cores by [kubectl run](https://github.com/kubernetes/kubernetes/blob/8caeec429ee1d2a9df7b7a41b21c626346b456fb/docs/user-guide/horizontal-pod-autoscaling/README.md#kubectl-run), this means average CPU usage of 250 milli-cores). See [here](https://github.com/kubernetes/kubernetes/blob/8caeec429ee1d2a9df7b7a41b21c626346b456fb/docs/design/horizontal-pod-autoscaler.md#autoscaling-algorithm) for more details on the algorithm. We may check the current status of autoscaler by running: ``` $ kubectl get hpa NAME REFERENCE TARGET CURRENT MINPODS MAXPODS AGE php-apache Deployment/php-apache/scale 50% 0% 1 20 14s ``` Please note that the current CPU consumption is 0% as we are not sending any requests to the server (the CURRENT column shows the average across all the pods controlled by the corresponding replication controller). #### Raising the Load Now, we will see how our autoscalers (Cluster Autoscaler and Horizontal Pod Autoscaler) react on the increased load of the server. We will start two infinite loops of queries to our server (please run them in different terminals): ``` $ kubectl run -i --tty load-generator --image=busybox /bin/sh Hit enter for command prompt $ while true; do wget -q -O- http://php-apache.default.svc.cluster.local; done ``` We need to wait a moment (about one minute) for stats to propagate. Afterwards, we will examine status of Horizontal Pod Autoscaler:

This section demonstrates how to run and expose a PHP-Apache server on Kubernetes using a custom Docker image. It walks through the steps of creating a deployment and service for the image, verifying their correct creation and operation. The section then introduces the Horizontal Pod Autoscaler (HPA) to automatically scale the number of pods based on CPU utilization. It explains how to create an HPA using the `kubectl autoscale` command and how to monitor its status.