Kubernetes - Configmap and Deployments

-

 


Below post is all about a request from a colleague.

1) There are 20 microservices.

2) All the microservices use a single configmap.

3) Change made to configmap should reflect in the microservices.

4) Microservices can also update the configmap as part of the deployment.

In this exampled, I am using nginx and redis deployment sharing a configmap.

First creating a configmap from a file:

root@masterk8s:/docker# cat cm.txt

app1=nginx

app2=redis

app3=memcached

root@masterk8s:/docker#

root@masterk8s:/docker# kubectl create configmap app-cm --from-file=cm.txt

configmap/app-cm created

root@masterk8s:/docker#

root@masterk8s:/docker# kubectl get configmap app-cm

NAME     DATA   AGE

app-cm   1      22s

root@masterk8s:/docker#

root@masterk8s:/docker# kubectl describe cm app-cm

Name:         app-cm

Namespace:    default

Labels:       <none>

Annotations:  <none>


Data

====

cm.txt:

----

app1=nginx

app2=redis

app3=memcached


Events:  <none>

root@masterk8s:/docker#

Creating a nginx deployment:

root@masterk8s:/docker# kubectl create deployment nginx --image=nginx --replicas=2 --dry-run=client -o yaml

root@masterk8s:/docker# cat nginx.yml

apiVersion: apps/v1

kind: Deployment

metadata:

  creationTimestamp: null

  labels:

    app: nginx

  name: nginx

spec:

  replicas: 2

  selector:

    matchLabels:

      app: nginx

  strategy: {}

  template:

    metadata:

      creationTimestamp: null

      labels:

        app: nginx

    spec:

      volumes:

      - name: cm-vol

        configMap:

          name: app-cm

      containers:

      - image: nginx

        name: nginx

        volumeMounts:

        - name: cm-vol

          mountPath: /etc/cfg

        resources: {}

status: {}

root@masterk8s:/docker#

root@masterk8s:/docker# kubectl apply -f nginx.yml

deployment.apps/nginx created

root@masterk8s:/docker#


root@masterk8s:/docker# kubectl get pods

NAME                     READY   STATUS    RESTARTS   AGE

nginx-5f8966bd76-mqnmq   1/1     Running   0          3m5s

nginx-5f8966bd76-zbjkg   1/1     Running   0          3m5s

root@masterk8s:/docker#

root@masterk8s:/docker# kubectl exec -it nginx-5f8966bd76-mqnmq -- cat /etc/cfg/cm.txt

app1=nginx

app2=redis

app3=memcached

root@masterk8s:/docker#

We have validated the configmaps are availabe on nginx deployment. 

Lets create another deployment using redis image using the same configmap.

root@masterk8s:/docker# cat redis.yml

apiVersion: apps/v1

kind: Deployment

metadata:

  creationTimestamp: null

  labels:

    app: redis

  name: redis

spec:

  replicas: 2

  selector:

    matchLabels:

      app: redis

  strategy: {}

  template:

    metadata:

      creationTimestamp: null

      labels:

        app: redis

    spec:

      volumes:

      - name: cm-vol

        configMap:

          name: app-cm

      containers:

      - image: redis

        name: redis

        volumeMounts:

        - name: cm-vol

          mountPath: /etc/cfg

        resources: {}

status: {}

root@masterk8s:/docker#

root@masterk8s:/docker# kubectl apply -f redis.yml

deployment.apps/redis created

root@masterk8s:/docker#

root@masterk8s:/docker# kubectl get pods

NAME                     READY   STATUS    RESTARTS   AGE

nginx-5f8966bd76-mqnmq   1/1     Running   0          6m4s

nginx-5f8966bd76-zbjkg   1/1     Running   0          6m4s

redis-d5675fbdc-29qqs    1/1     Running   0          26s

redis-d5675fbdc-6h2rs    1/1     Running   0          25s

root@masterk8s:/docker#


root@masterk8s:/docker# kubectl exec -it redis-d5675fbdc-29qqs -- cat /etc/cfg/cm.txt

app1=nginx

app2=redis

app3=memcached

root@masterk8s:/docker#


Now, Lets modify the configmap by removing the last line app3=memcached.


root@masterk8s:/docker# kubectl edit configmap app-cm

configmap/app-cm edited

root@masterk8s:/docker# kubectl describe cm app-cm

Name:         app-cm

Namespace:    default

Labels:       <none>

Annotations:  <none>


Data

====

cm.txt:

----

app1=nginx

app2=redis


Events:  <none>

root@masterk8s:/docker#


Now, the existing deployment should pickup the changes dynamically.


root@masterk8s:/docker# kubectl exec -it redis-d5675fbdc-29qqs -- cat /etc/cfg/cm.txt

app1=nginx

app2=redis

root@masterk8s:/docker#


root@masterk8s:/docker# kubectl exec -it nginx-5f8966bd76-mqnmq -- cat /etc/cfg/cm.txt

app1=nginx

app2=redis

root@masterk8s:/docker#





Comments

Post a Comment

Popular posts from this blog

SRE/DevOps Syllabus

-
Image
  DEVOPS/SRE Principles. Git What is Git? Architecture of Git. Working principle of Git. Create and cloning a repo. Version control branching. Version control commit. Version control managing workflows. Git hooks. Git Reflog. Git Stash. Git Cherry Picking. Undoing changes in different states of Git. Git based terraform template management. AWS CI/CD SDLC Automation. Code Commit. Code Build. Code Deployment. Code Pipeline. Elastic Beankstalk. Code Artifact. CodeGuru. Terraform Terraform Basics. Terraform State. Working with Terraform. Terraform with AWS. Remote State. Terraform Provisioners. Terraform Import, Tainting and Debugging. Terraform Modules. Terraform Functions and Conditional Expressions. Automation using Python - AWS AWS lambda. Automating EC2 with Lambda. Automating S3 with Lambda. Automating VPC with Lambda. Cost optimization with Lambda. SNS,SQS and SES with Python. Managing and Automating AWS Security with Python. Kubernetes - CKAD Application Developer. Kubernetes A...
Read more

AWS Code Commit - CI/CD Series Part 1

-
Image
  This is a multi-part series to show how to implement a CI/CD pipeline in AWS. In this post, We will see how to use AWS Code Commit. AWS CodeCommit is a fully managed source control service that allows you to store and manage your code securely in the cloud.  It provides a private Git repository for your code and supports all Git commands and workflows. CodeCommit also integrates with other AWS services like AWS CodePipeline and AWS CodeBuild, allowing you to automate your entire software release process. This can help you streamline your development workflows and improve the overall efficiency of your team. I created a repo from AWS CodeCommit -> Create Repository. And I begin with cloning the repo locally. So that I can make changes and push it. To clone the repo click on "HTTPS" under Clone URL. I make changes to index.html file. Now push it to AWS CodeCommit. Let’s verify the changes in AWS Code commit. Changes are reflected in AWS CodeCommit. We are done with Part ...
Read more

Docker - Preventing IP overlapping

-
Image
  What is IP address overlapping? When the container IP address overlaps with another IP external, then the application running on the container is not accessible from outside due to the IP address overlapping.  NOTE: This IP address overlapping can happen on the bridge interface IP or docker container IP. Let's see how to address this IP overlapping issue on the bridge interface. I already have a running container.  root@demo:~# docker run -d --name web --network mynet1 nginx:alpine 268647e11011d513d2357ce1c81e0f48787038a83d01d028d31a5b29dbdb885b root@demo:~# docker container ls CONTAINER ID   IMAGE          COMMAND                  CREATED         STATUS         PORTS     NAMES 268647e11011   nginx:alpine   "/docker-entrypoint.…"   4 seconds ago   Up 3 seconds   80/tcp  ...
Read more