Fix PHP/Apache Issue

1. Kubernetes Resources

Especially in Production Kubernetes Clusters, CPU and Memory are considered precious resources. Cluster Operators will normally require you to specify the amount of CPU and Memory your Pod or Service will require in the deployment, so they can have the Cluster automatically manage on which Node(s) your solution will be placed.

You do this by placing a Resource section in the deployment of your application/Pod

Example:

resources:
  limits:         # Maximum amount of CPU & memory for peek use
    cpu: "8"      # Maximum of 8 cores of CPU allowed at for peek use
    memory: "8Mi" # Maximum allowed 8Mb of memory
  requests:       # Request are the expected amount of CPU & memory for normal use
    cpu: "6"      # Requesting 4 cores of a CPU
    memory: "4Mi" # Requesting 4Mb of memory

More information can be found here: Resource Management for Pods and Containers

If your application or Pod will go over the limits set in your deployment, Kubernetes will kill and restart your Pod to protect the other applications on the Cluster.

Another scenario that you will run into is when there is not enough Memory or CPU on a Node. In that case, the Cluster will try to reschedule your Pod(s) on a different Node with more space.

If that fails, or if there is not enough space when you deploy your application, the Cluster will put your workload/deployment in schedule mode until there is enough room on any of the available Nodes to deploy the Pods according to their limits.

2. Fix PHP/Apache Deployment

Workshop Question

Before we start, let’s check the current status of the PHP/Apache deployment. Under Alerts & Detectors which detector has fired? Where else can you find this information?

To fix the PHP/Apache StatefulSet, edit ~/workshop/k3s/php-apache.yaml using the following commands to reduce the CPU resources:

vim ~/workshop/k3s/php-apache.yaml

Find the resources section and reduce the CPU limits to 1 and the CPU requests to 0.5:

resources:
  limits:
    cpu: "1"
    memory: "8Mi"
  requests:
    cpu: "0.5"
    memory: "4Mi"

Save the changes you have made. (Hint: Use Esc followed by :wq! to save your changes).

Now, we must delete the existing StatefulSet and re-create it. StatefulSets are immutable, so we must delete the existing one and re-create it with the new changes.

kubectl delete statefulset php-apache -n apache

Now, deploy your changes:

kubectl apply -f ~/workshop/k3s/php-apache.yaml -n apache

3. Validate the changes

You can validate the changes have been applied by running the following command:

kubectl describe statefulset php-apache -n apache

Validate the Pod is now running in Splunk Observability Cloud.

Workshop Question

Is the Apache Web Servers dashboard showing any data now?

Tip: Don’t forget to use filters and time frames to narrow down your data.

Monitor the Apache web servers Navigator dashboard for a few minutes.

Workshop Question

What is happening with the # Hosts reporting chart?

4. Fix the memory issue

If you navigate back to the Apache dashboard, you will notice that metrics are no longer coming in. We have another resource issue and this time we are Out of Memory. Let’s edit the stateful set and increase the memory to what is shown in the image below:

kubectl edit statefulset php-apache -n apache

resources:
  limits:
    cpu: "1"
    memory: 16Mi
  requests:
    cpu: 500m
    memory: 12Mi

Save the changes you have made.

Hint

kubectl edit will open the contents in the vi editor, use Esc followed by :wq! to save your changes.

Because StatefulSets are immutable, we must delete the existing Pod and let the StatefulSet re-create it with the new changes.

kubectl delete pod php-apache-0 -n apache

Validate the changes have been applied by running the following command:

kubectl describe statefulset php-apache -n apache