Task Information
We have a web server container running the nginx image. The access and error logs generated by the web server are not critical enough to be placed on a persistent volume. However, Nautilus developers need access to the last 24 hours of logs so that they can trace issues and bugs. Therefore, we need to ship the access and error logs for the web server to a log-aggregation service. Following the separation of concerns principle, we implement the Sidecar pattern by deploying a second container that ships the error and access logs from nginx. Nginx does one thing, and it does it well—serving web pages. The second container also specializes in its task—shipping logs. Since containers are running on the same Pod, we can use a shared emptyDir volume to read and write logs.
Create a pod named webserver.
Create an emptyDir volume shared-logs.
Create two containers from nginx and ubuntu images with latest tag only and remember to mention tag i.e nginx:latest, nginx container name should be nginx-container and ubuntu container name should be sidecar-container on webserver pod.
Add command on sidecar-container "sh","-c","while true; do cat /var/log/nginx/access.log /var/log/nginx/error.log; sleep 30; done"
Mount the volume shared-logs on both containers at location /var/log/nginx, all containers should be up and running.
Note: The kubectl utility on jump_host has been configured to work with the kubernetes cluster.
Task Solutions
Step 1: Create the Pod YAML configuration
Create a file named webserver-pod.yaml:
cat > webserver-pod.yaml << EOF
apiVersion: v1
kind: Pod
metadata:
name: webserver
spec:
containers:
- name: nginx-container
image: nginx:latest
volumeMounts:
- name: shared-logs
mountPath: /var/log/nginx
- name: sidecar-container
image: ubuntu:latest
command: ["sh", "-c", "while true; do cat /var/log/nginx/access.log /var/log/nginx/error.log; sleep 30; done"]
volumeMounts:
- name: shared-logs
mountPath: /var/log/nginx
volumes:
- name: shared-logs
emptyDir: {}
EOF
Step 2: Create the pod
Apply the configuration to create the pod:
kubectl apply -f webserver-pod.yaml
Step 3: Verify the pod is running
Check if the pod is created and both containers are running:
kubectl get pod webserver
Step 4: Check the detailed status of the pod
Verify both containers are properly configured:
kubectl describe pod webserver
Step 5: Test the sidecar container logs
Check the logs of the sidecar container to see if it's reading the nginx logs:
kubectl logs webserver -c sidecar-container
Step 6: Generate some web traffic to create logs
Let's generate some access to the nginx server to create log entries:
First, find the nginx container's IP
kubectl get pod webserver -o wide
Then access the nginx server (you can use the pod IP or port-forward):
Using port-forward
In one terminal, set up port forwarding
kubectl port-forward webserver 8080:80
Step 7: Verify the sidecar is shipping logs
After generating some traffic, check the sidecar container logs again:
kubectl logs webserver -c sidecar-container
Step 8: Verify volume mounting
Check that both containers have the volume mounted correctly:
Check nginx container
kubectl exec -it webserver -c nginx-container -- ls -la /var/log/nginx/
Check sidecar container
kubectl exec -it webserver -c sidecar-container -- ls -la /var/log/nginx/
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