How can I update kuberenet pod based on configuration change? - nginx

Question

I have a configuration file like below. I deploy it to EKS cluster successfully. However, when I change the nginx-conf ConfigMap and run kubectl apply command, it doesn't seem to update the nginx.config in the pod. I tried to login to the pod and look at the file /etc/nginx/nginx.config but its content is still the old one.
I have tried to run kubectl rollout status deployment sidecar-app but it doesn't help.
And it shows the updated config map when I run kubectl describe configmap nginx-conf.
It seems the container doesn't take the config map change. How can I apply the changes without deleting the pod?
apiVersion: v1
kind: ConfigMap
metadata:
name: nginx-conf
data:
nginx.conf: |
user nginx;
worker_processes 1;
events {
worker_connections 10240;
}
http {
server {
listen 8080;
server_name localhost;
location / {
proxy_pass http://localhost:9200/;
}
location /health {
proxy_pass http://localhost:9200/_cluster/health;
}
}
}
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: sidecar-app
namespace: default
spec:
replicas: 1
selector:
matchLabels:
name: sidecar-app
template:
metadata:
labels:
name: sidecar-app
spec:
containers:
- name: nginx
image: nginx:latest
ports:
- name: http
containerPort: 8080
volumeMounts:
- name: nginx-conf
mountPath: /etc/nginx/nginx.conf
subPath: nginx.conf
readOnly: true
volumes:
- name: nginx-conf
configMap:
name: nginx-conf
items:
- key: nginx.conf
path: nginx.conf
---
apiVersion: v1
kind: Service
metadata:
name: sidecar-entrypoint
spec:
selector:
name: sidecar-app
ports:
- port: 8080
targetPort: 8080
protocol: TCP
type: NodePort
---
apiVersion: extensions/v1beta1
kind: Ingress
metadata:
name: sidecar-ingress-1
namespace: default
annotations:
kubernetes.io/ingress.class: alb
alb.ingress.kubernetes.io/group.name: sidecar-ingress
alb.ingress.kubernetes.io/scheme: internet-facing
alb.ingress.kubernetes.io/target-type: ip
alb.ingress.kubernetes.io/group.order: '2'
alb.ingress.kubernetes.io/healthcheck-path: /health
# alb.ingress.kubernetes.io/healthcheck-port: '8080'
spec:
rules:
- http:
paths:
- path: /*
backend:
serviceName: sidecar-entrypoint
servicePort: 8080

Answer 1

Kubernetes treats POD and Configmap as a different/separate object and pods don't automatically restart on specific Configmap version.
There are few alternatives to achieve this.
1 ) Reloader: https://github.com/stakater/Reloader
kind: Deployment
metadata:
annotations:
reloader.stakater.com/auto: "true"
spec:
template: metadata:
configHash annotation.
https://blog.questionable.services/article/kubernetes-deployments-configmap-change/
Use wave.
https://github.com/wave-k8s/wave
You can use kubectl rollout restart deploy/sidecar-app but this will restart the pods with zero downtime. Rolling updates allow Deployments' update to take place with zero downtime by incrementally updating Pods instances with new ones.