Working with Namespaces and Services in Kubernetes

Author: Vaishnavi Shivde

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In the dynamic realm of Kubernetes (K8s), mastering foundational concepts like Namespaces and Services is crucial for orchestrating containerized applications effectively. Let’s embark on a journey to explore the significance of Namespaces and Services within the Kubernetes ecosystem.

Namespaces in Kubernetes:

In Kubernetes, Namespaces are used to create isolated environments for resources. Each Namespace is like a separate cluster within the same physical cluster.

Use Cases for Namespaces

• Multi-Tenancy: Support multiple users or teams within the same cluster by isolating resources.
• Environment Segmentation: Separate development, testing, and production environments within the same cluster.
• Resource Quotas: Apply resource limits and quotas to specific namespaces to control resource usage.
• Access Control: Implement role-based access control (RBAC) to manage permissions at the namespace level.
• Organizational Structure: Reflect the organizational hierarchy by creating namespaces for different departments or projects.

Default Namespaces 🛠️

• default: The default namespace for resources without an explicit namespace.
• kube-system: Contains Kubernetes system components.
• kube-public: A special namespace readable by all users, typically used for cluster information.
• kube-node-lease: Used for node lease objects for heartbeats.

Service in Kubernetes:

In Kubernetes (k8s), a “Service” is an abstraction that defines a logical set of Pods and a policy by which to access them, sometimes called a microservice. Kubernetes Services enable Pods to communicate with each other and with other parts of the system, ensuring reliable network connectivity and load balancing.

Use Cases:

• Microservices Communication: Services enable different microservices within a cluster to communicate with each other reliably.
• External API Exposure: Exposing an internal API to external users via a LoadBalancer service.
• Internal Load Balancing: Distributing requests among backend Pods for a scalable web application.

Task:01

In this section, we will deploy a Nginx web server within a Kubernetes Namespace and expose it as a Service.

1. Create a Namespace for your Deployment

 kubectl create namespace nginx

You should see something like this:

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

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

3. Apply the updated deployment using the command:

 kubectl apply -f deployment.yml

4. Verify that the Deployment is created by running:

 kubectl get deployments -n nginx

You should see something like this:

5. Verify that the Pods are running by running:

kubectl get pods -n nginx

You should see something like this:

Task:02

Read about Services, Load Balancing, and Networking in Kubernetes.

Types of Services 🧩

1. ClusterIP (Default) 🌐
   • Description: Exposes the Service on an internal IP in the cluster, accessible only within the cluster.
   • Use Case: Internal communication between services within the same cluster.
   • Example:

apiVersion: v1
  kind: Service
  metadata:
    name: my-service
  spec:
    selector:
      app: MyApp
    ports:
      - protocol: TCP
        port: 80
        targetPort: 9376
    type: ClusterIP

2. NodePort 🔓

• Description: Exposes the Service on each Node’s IP at a static port (the NodePort). Accessible externally using <NodeIP>:<NodePort>.
• Use Case: Direct access to a service from outside the cluster without a load balancer.
• Example:

apiVersion: v1
  kind: Service
  metadata:
    name: my-service
  spec:
    selector:
      app: MyApp
    ports:
      - protocol: TCP
        port: 80
        targetPort: 9376
        nodePort: 30007
    type: NodePort

1. LoadBalancer ⚖️
   • Description: Exposes the Service externally using a cloud provider’s load balancer.
   • Use Case: Automatically provision a load balancer for your service in a cloud environment.
   • Example:

apiVersion: v1
  kind: Service
  metadata:
    name: my-service
  spec:
    selector:
      app: MyApp
    ports:
      - protocol: TCP
        port: 80
        targetPort: 9376
    type: LoadBalancer

4. ExternalName 🌏

• Description: Maps a Service to the contents of the externalName field (e.g., a CNAME record), without proxying any traffic.
• Use Case: Redirects requests to an external service (e.g., an external database or third-party service).
• Example:

apiVersion: v1
  kind: Service
  metadata:
    name: my-service
  spec:
    type: ExternalName
    externalName: my.external.service.com

Conclusion:

Namespaces and Services are fundamental pillars of Kubernetes, empowering users to organize resources efficiently and streamline networking within the cluster. By understanding the roles and functionalities of Namespaces and Services, Kubernetes enthusiasts can navigate the intricate landscape of container orchestration with confidence and agility.

Embrace the power of Namespaces and Services in Kubernetes, and embark on a transformative journey towards scalable, resilient, and dynamically orchestrated applications.

Let me know if you need further insights or have any questions! 🚀

Author: Vaishnavi Shivde

• LinkedIn