Introduction
A Deployment in Kubernetes (K8s) is a crucial resource that orchestrates the deployment and scaling of containerized applications. It offers a declarative approach to specifying the desired state of an application, including the number of instances (replicas) that should be actively running. This ensures applications are always available and responsive to user demands.
What is Deployment in K8s?
A Deployment provides a configuration for updates for Pods and ReplicaSets.
In Kubernetes, a deployment is a resource object that manages the deployment and scaling of a set of containerized applications. It provides a declarative way to define the desired state of an application, including the number of replicas (instances) that should be running.
Key characteristics of a Kubernetes deployment:
Desired State: It ensures that a specified number of replicas of a containerized application are running at any given time.
Rolling Updates: It supports updates to applications without downtime by gradually replacing old pods with new ones.
Rollback: If an update causes issues, a deployment can be rolled back to a previous version.
Scaling: It allows both manual and automatic scaling of the number of replicas to meet demand.
Self-healing: If a pod fails, Kubernetes automatically replaces it to maintain the desired state.
Task-1:
Create a Deployment file to demonstrate deploying an nginx image on K8s, showcasing "Auto-healing" and "Auto-Scaling" features.
Deploying a Simple Nginx Pod in Minikube: Step-by-Step Guide
To set up Minikube locally, refer to my ---> previous blog <--- post for detailed instructions.
Step 1: Start Minikube
minikube start
Step 2: Define a Deployment YAML File
Create a file named deployment.yaml and add the following content:
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx-deployment
namespace: nginx
labels:
app: nginx
spec:
replicas: 2
selector:
matchLabels:
app: nginx
template:
metadata:
namespace: nginx
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:latest
ports:
- containerPort: 80
Step 3: Apply the YAML File
Apply the YAML file to create the deployment:
kubectl apply -f first-deployment.yaml
Step 4: Check the Status of the Deployment
kubectl get deployments -n nginx
2nd and 3rd are pods that are created now
After completing these steps, you will have successfully deployed an Nginx deployment with two replicas and checked its status.
Task-2:
Create one Deployment file to deploy a sample todo-app on K8s using "Auto-healing" and "Auto-Scaling" feature
Step 1: Clone the Repository from GitHub
- GitHub Repo Link: Git Hub
Step 2: Build the Image
docker build -t <dockerhub_username>/node-todo:latest .
Step 3: Push the Docker Image to Docker Hub
docker login
docker push <dockerhub_username>/node-todo:latest
Step 4: Add a deployment.yaml File
apiVersion: apps/v1
kind: Deployment
metadata:
name: todo-deployment
labels:
name: todo
spec:
replicas: 2
selector:
matchLabels:
app: todo
template:
metadata:
labels:
app: todo
spec:
containers:
- name: todo-container
image: simbaa815/node-todo:latest
ports:
- containerPort: 8000
Step 5: Apply the Deployment to Your K8s (Minikube) Cluster
kubectl apply -f deployment.yaml
Step 6: Get Pods
kubectl get pods
Step 7: Delete a Pod for Testing Auto Healing
kubectl delete pod <pod_name>
As you can see, a new pod will be automatically created, demonstrating the concept of Auto Healing.
Conclusion:
Kubernetes Deployments streamline application management, ensuring seamless updates and scaling.
Stay tuned for more in-depth Kubernetes insights in our upcoming blogs. Keep learning and stay ahead! 🚀
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