Kubernetes Sidecar Containers

Question : We have a web server container running the nginx image. The access and error logs produced 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 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 volumemount name: 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 volume /var/log/nginx on both containers, all containers should be up and running.

Please Note:-  Perform the below commands based on your question server,  user name & other details that might differ. So please read the task carefully before executing it. All the Best 👍

Solution:  

1. At first  kubectl  utility configure and working from jump server, run below commands    

thor@jump_host /$ kubectl get services NAME         TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)   AGE kubernetes   ClusterIP   10.96.0.1    <none>        443/TCP   58s thor@jump_host /$ thor@jump_host /$ kubectl get pods No resources found in default namespace. thor@jump_host /$

2.  Create yaml  file with all the parameters , you can copy form git lab

      https://gitlab.com/nb-tech-support/devops.git

    ( Refer Below Video for more clarity )

thor@jump_host /$ vi /tmp/webserver.yaml thor@jump_host /$ cat  /tmp/webserver.yaml apiVersion: v1 kind: Pod metadata:   name: webserver   labels:     name: webserver spec:   volumes:     - name: shared-logs       emptyDir: {}   containers:     - name: nginx-container       image: nginx:latest       volumeMounts:         - name: shared-logs           mountPath: /var/log/nginx     - name: sidecar-container       image: ubuntu:latest       command:         [           "/bin/bash",           "-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 thor@jump_host /$

4.  Run the below command to create a pod    

thor@jump_host /$ kubectl create -f /tmp/webserver.yaml pod/webserver created thor@jump_host /$

5.  Wait for  pods to get running status      

thor@jump_host /$  kubectl get pods NAME        READY   STATUS    RESTARTS   AGE webserver   2/2     Running   0          49s thor@jump_host /$

6. Validate the task by running below command

thor@jump_host /$ kubectl describe pods Name:         webserver Namespace:    default Priority:     0 Node:         node01/172.17.0.26 Start Time:   Thu, 15 Jul 2021 14:04:04 +0000 Labels:       name=webserver Annotations:  <none> Status:       Running IP:           10.244.1.2 IPs:   IP:  10.244.1.2 Containers:   nginx-container:     Container ID:   docker://2b8b73cac375285934371dbadf497268ca297581e4e19a63d11cef3a5c4923f1     Image:          nginx:latest     Image ID:       docker-pullable://nginx@sha256:353c20f74d9b6aee359f30e8e4f69c3d7eaea2f610681c4a95849a2fd7c497f9     Port:           <none>     Host Port:      <none>     State:          Running       Started:      Thu, 15 Jul 2021 14:04:11 +0000     Ready:          True     Restart Count:  0     Environment:    <none>     Mounts:       /var/log/nginx from shared-logs (rw)       /var/run/secrets/kubernetes.io/serviceaccount from default-token-ffr4n (ro)   sidecar-container:     Container ID:  docker://4f30404e84992da1d83c069bbcc925fd509a18600c9f7fa75415e749d3936340     Image:         ubuntu:latest     Image ID:      docker-pullable://ubuntu@sha256:b3e2e47d016c08b3396b5ebe06ab0b711c34e7f37b98c9d37abe794b71cea0a2     Port:          <none>     Host Port:     <none>     Command:       /bin/bash       -c       while true; do cat /var/log/nginx/access.log /var/log/nginx/error.log; sleep 30; done     State:          Running       Started:      Thu, 15 Jul 2021 14:04:14 +0000     Ready:          True     Restart Count:  0     Environment:    <none>     Mounts:       /var/log/nginx from shared-logs (rw)       /var/run/secrets/kubernetes.io/serviceaccount from default-token-ffr4n (ro) Conditions:   Type              Status   Initialized       True   Ready             True   ContainersReady   True   PodScheduled      True Volumes:   shared-logs:     Type:       EmptyDir (a temporary directory that shares a pod's lifetime)     Medium:         SizeLimit:  <unset>   default-token-ffr4n:     Type:        Secret (a volume populated by a Secret)     SecretName:  default-token-ffr4n     Optional:    false QoS Class:       BestEffort Node-Selectors:  <none> Tolerations:     node.kubernetes.io/not-ready:NoExecute op=Exists for 300s                  node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events:   Type    Reason     Age    From               Message   ----    ------     ----   ----               -------   Normal  Scheduled  2m16s  default-scheduler  Successfully assigned default/webserver to node01   Normal  Pulling    2m14s  kubelet            Pulling image "nginx:latest"   Normal  Pulled     2m9s   kubelet            Successfully pulled image "nginx:latest" in 4.949468199s   Normal  Created    2m8s   kubelet            Created container nginx-container   Normal  Started    2m8s   kubelet            Started container nginx-container   Normal  Pulling    2m8s   kubelet            Pulling image "ubuntu:latest"   Normal  Pulled     2m5s   kubelet            Successfully pulled image "ubuntu:latest" in 2.950736172s   Normal  Created    2m5s   kubelet            Created container sidecar-container   Normal  Started    2m5s   kubelet            Started container sidecar-container thor@jump_host /$

7.  Click on Finish & Confirm to complete the task successful

Happy Learning!!!!

Apart from this if you need more clarity,  I have made a  tutorial video on this , 

please go through and share your comments. Like and share the knowledge