🚀 Kubernetes Namespaces & Services.

📌 Understanding Namespaces in Kubernetes

Namespaces in Kubernetes provide a way to create isolated environments within a cluster. They help organize and manage resources efficiently, especially in multi-team or multi-project scenarios.

🔹 Key Features of Namespaces:

• Isolation: Resources within a Namespace do not interfere with those in another.

• Logical Grouping: Makes managing large applications easier.

• Access Control: Helps in applying resource limits and security policies.

• Default Namespace: If no Namespace is specified, resources are created in the default Namespace.

👉 Create a Namespace using:

kubectl create namespace my-namespace

---

📌 Understanding Services in Kubernetes

A Service provides a stable way to access and communicate with Pods, ensuring connectivity even if Pods are restarted or rescheduled.

🔹 Types of Kubernetes Services:

1. ClusterIP (Default):

   • Exposes the Service within the cluster.

   • Used for internal communication between Pods.

2. NodePort:

   • Exposes the Service on a static port on each node.

   • Can be accessed externally using <NodeIP>:<NodePort>.

3. LoadBalancer:

   • Uses an external load balancer to expose the Service outside the cluster.

   • Common in cloud environments like AWS, GCP, and Azure.

4. ExternalName:

   • Maps the Service to an external DNS name.

   • Useful for connecting to external services.

5. Headless Service (No ClusterIP):

   • Used when direct Pod discovery is required instead of a single Service IP.

   • Does not assign a ClusterIP.

   • Kubernetes DNS returns the IP addresses of all matching Pods, allowing direct communication.

---

✅ Task 1: Create a Namespace for Your Deployment

1️⃣ Create a Namespace:

kubectl create namespace my-namespace

2️⃣ Update the deployment.yml file to include the Namespace:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-app
  namespace: my-namespace      # Specify the Namespace
spec:
  replicas: 2
  selector:
    matchLabels:
      app: my-app
  template:
    metadata:
      labels:
        app: my-app
    spec:
      containers:
      - name: my-container
        image: my-image:latest

3️⃣ Apply the updated deployment:

kubectl apply -f deployment.yml -n my-namespace

4️⃣ Verify the Namespace creation:

kubectl get namespaces

---

✅ Task 2: Learn About Services, Load Balancing & Networking

🔹 How Kubernetes Services Expose and Route Traffic to Pods

• Kubernetes Services act as a stable entry point to access Pods, even if Pods are restarted or rescheduled.

• They use labels and selectors to route traffic to the correct set of Pods.

• When a request comes to a Service, it distributes it across multiple Pods matching the selector.

• Example: A backend application with multiple replicas can be accessed via a single Service.

---

🔹 Networking in Kubernetes and How Pods Communicate

• Each Pod in Kubernetes has a unique IP address.

• Pods can communicate directly within the same Node or across Nodes using Kubernetes networking rules.

• Kube-proxy manages networking rules that allow traffic between Services and Pods.

• CNI (Container Network Interface) plugins like Calico, Flannel, and Cilium are used to define network policies.

📌 Common Network Scenarios:
✔ Pod-to-Pod Communication – Direct IP-based communication.
✔ Pod-to-Service Communication – Pods use the Service name (DNS) to connect to backend Pods.
✔ Ingress Communication – External traffic enters the cluster via an Ingress Controller.

---

🔹 Load Balancing Mechanisms in Kubernetes

Load balancing ensures that traffic is distributed efficiently across multiple Pods to improve availability and reliability.

✅ Types of Load Balancing in Kubernetes:

1. Internal Load Balancing:

   • Kubernetes Services distribute traffic among multiple Pods.

   • Uses ClusterIP (for internal traffic) and kube-proxy to route requests.

2. External Load Balancing:

   • Uses LoadBalancer Service (if running in a cloud environment).

   • The cloud provider creates an external Load Balancer to distribute traffic.

3. Ingress Load Balancing:

   • Manages HTTP/HTTPS traffic and routes requests to different Services.

   • Requires an Ingress Controller like Nginx or Traefik.

📌 Example of LoadBalancer Service:

apiVersion: v1
kind: Service
metadata:
  name: my-loadbalancer
spec:
  selector:
    app: my-app
  type: LoadBalancer
  ports:
    - port: 80
      targetPort: 8080

---

📌 Summary Table