kubectl cluster-info , Core DNS functionalities

Kubernetes control plane is running at https://127.0.0.1:64053

CoreDNS is running at https://127.0.0.1:64053/api/v1/namespaces/kube-system/services/kube-dns:dns/proxy

What it is:

The "control plane" is the brain of your Kubernetes cluster. It's a collection of processes that manage the overall state of the cluster.

Components of Control Plane:

kube-apiserver: Front-end that exposes Kubernetes API (what you're connecting to)

etcd: Distributed key-value store (cluster database)

kube-scheduler: Assigns pods to nodes

kube-controller-manager: Runs controller processes

cloud-controller-manager: Manages cloud provider specifics

What "running at https://127.0.0.1:64053" means:

Your Kubernetes API server is accessible locally on port 64053

kubectl commands communicate with this endpoint

This is your gateway to manage the cluster

2. CoreDNS

What it is:

CoreDNS is the DNS server for your Kubernetes cluster. It provides service discovery and DNS resolution within the cluster.

Why Kubernetes Needs DNS:

Service Discovery Example:

# Without DNS - you'd need to know IP addresses

apiVersion: v1

kind: Pod

metadata:

  name: frontend

spec:

  containers:

  - name: app

    image: nginx

    env:

    - name: BACKEND_URL

      value: "10.244.1.5:8080"  # Hard-coded IP - BAD!

# With DNS - use service names

apiVersion: v1

kind: Pod

metadata:

  name: frontend

spec:

  containers:

  - name: app

    image: nginx

    env:

    - name: BACKEND_URL

      value: "backend-service.dev.svc.cluster.local:8080"  # DNS name - GOOD!

Real-world Examples of CoreDNS in Action

Example 1: Service-to-Service Communication

# Database Service

apiVersion: v1

kind: Service

metadata:

  name: database

  namespace: dev

spec:

  selector:

    app: postgres

  ports:

  - port: 5432

---

# Application Pod that connects to database

apiVersion: v1

kind: Pod

metadata:

  name: web-app

  namespace: dev

spec:

  containers:

  - name: app

    image: my-app:latest

    env:

    - name: DB_HOST

      value: "database.dev.svc.cluster.local"  # CoreDNS resolves this!

    - name: DB_PORT

      value: "5432"

Example 2: Pods Finding Each Other

# From inside any pod, you can resolve services:

nslookup database.dev.svc.cluster.local

# CoreDNS resolves this to the service IP

DNS Resolution Hierarchy in Kubernetes

CoreDNS resolves names in this order:

Pod-name.namespace.pod.cluster.local (individual pods)

service.namespace.svc.cluster.local (services)

External DNS names (google.com, etc.)

How CoreDNS Works with Your FastAPI Application

apiVersion: v1

kind: Service

metadata:

  name: app-svc

  namespace: dev

spec:

  selector:

    app: llm-api

  ports:

  - port: 8000

CoreDNS allows:

Pods in dev namespace to find your service via app-svc.dev.svc.cluster.local

Other services to communicate with your FastAPI app

Ingress controller to route traffic to your service