DNS in Kubernetes

1. Introduction

DNS (Domain Name System) is a critical component in Kubernetes, enabling the discovery of services and facilitating communication between pods. The Kubernetes DNS system allows users to access services by name rather than by IP address.

2. Key Concepts

3. DNS Resolution in Kubernetes

Kubernetes uses CoreDNS as the default DNS server which runs as a pod within the cluster. It listens for DNS queries and resolves service names to their corresponding IP addresses.

DNS Resolution Flow

        graph TD;
            A[Pod] -->|DNS Query| B[CoreDNS];
            B -->|Service Name| C[Service];
            C -->|IP Address| D[Pod];
            D -->|Response| A;
    

4. Configuring DNS

To configure DNS in Kubernetes, you typically define services that will be accessible by name. Below is an example of creating a service:

apiVersion: v1
kind: Service
metadata:
  name: my-service
spec:
  selector:
    app: my-app
  ports:
    - protocol: TCP
      port: 80
      targetPort: 8080
  type: ClusterIP

This YAML file defines a service named `my-service` that routes traffic to pods labeled with `app: my-app` on port 80.

5. Best Practices

• Use meaningful service names to simplify identification.
• Regularly monitor CoreDNS performance and logs for issues.
• Implement health checks for your services to ensure proper routing.

6. FAQ