Apache web server custom index kubernetes - apache

Question

I have deployed a apache web server on kubernetes cluster using standard httpd image from dockerhub. I want to make changes to index file so that it prints the container id instead of default index file. How can i achieve this?

Answer 1

Answering the question:
How can I have a Apache container in Kubernetes that will output the id of the container in the index.html or other .html file.
One of the ways how it could be handled is by a lifecycle hooks (specifically postStart):
PostStart
This hook is executed immediately after a container is created. However, there is no guarantee that the hook will execute before the container ENTRYPOINT. No parameters are passed to the handler.
-- Kubernetes.io: Docs: Concepts: Containers: Container lifecycle hooks: Container hooks
As for the example of such how setup could be implemented:
apiVersion: apps/v1
kind: Deployment
metadata:
name: apache
labels:
app: apache
spec:
replicas: 3
selector:
matchLabels:
app: apache
template:
metadata:
labels:
app: apache
spec:
containers:
- name: apache
image: httpd # <-- APACHE IMAGE
# LIFECYCLE DEFINITION START
lifecycle:
postStart:
exec:
command: ["/bin/sh", "-c", "echo $HOSTNAME > htdocs/hostname.html"]
# LIFECYCLE DEFINITION END
ports:
- containerPort: 80
Taking a specific look on:
command: ["/bin/sh", "-c", "echo $HOSTNAME > htdocs/hostname.html"]
This part will write/save a hostname of the container to the hostname.html
To check if each of Pod has the hostname.html you can create a Service and run either:
$ kubectl port-forward svc/apache 8080:80 -> curl localhost:8080/hostname.html
$ kubectl run -it --rm nginx --image=nginx -- /bin/bash -> curl apache/hostname.html
Additional resources:
Kubernetes.io: Docs: Tasks: Configure pod container: Attach handler lifecycle event: Define postStart and preStop handlers