Solutions for Service Tasks

This document contains the solutions and verification steps for the Service practice questions.

---

Solution 1: ClusterIP — Basic Service (CKA)

Manifest:

apiVersion: v1
kind: Namespace
metadata:
  name: marketing
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-app
  namespace: marketing
spec:
  replicas: 2
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
      - name: nginx
        image: nginx:alpine
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: internal-web
  namespace: marketing
spec:
  type: ClusterIP
  selector:
    app: web
  ports:
  - port: 80
    targetPort: 80

Commands:

# Apply manifest
kubectl apply -f solution1.yaml

# Verify endpoints
kubectl get endpoints internal-web -n marketing

# Test connectivity from a pod
kubectl run test --rm -it --image=busybox -n marketing -- wget -qO- internal-web:80

---

Solution 2: NodePort — Basic Exposure (CKA)

Manifest:

apiVersion: v1
kind: Namespace
metadata:
  name: public-access
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: front-door
  namespace: public-access
spec:
  replicas: 2
  selector:
    matchLabels:
      app: front-door
  template:
    metadata:
      labels:
        app: front-door
    spec:
      containers:
      - name: nginx
        image: nginx
---
apiVersion: v1
kind: Service
metadata:
  name: global-entry
  namespace: public-access
spec:
  type: NodePort
  selector:
    app: front-door
  ports:
  - port: 80
    targetPort: 80
    nodePort: 31050

Commands:

# Apply manifest
kubectl apply -f solution2.yaml

# Verify NodePort assignment
kubectl get svc global-entry -n public-access

# Access from external (replace <node-ip> with actual node IP)
curl http://<node-ip>:31050

---

Solution 3: Imperative Commands

Commands:

# 1. Create the pod
kubectl run manual-pod --image=httpd:alpine --labels="app=manual"

# 2. Expose imperatively
kubectl expose pod manual-pod --name=fast-svc --port=80 --target-port=8080

# 3. Generate YAML without creation
kubectl expose pod manual-pod --name=nodeport-svc --type=NodePort --port=80 --dry-run=client -o yaml > nodeport.yaml

---

Solution 4: Multi-Port & Named Ports (CKA)

Manifest:

apiVersion: v1
kind: Namespace
metadata:
  name: services-test
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-gateway
  namespace: services-test
spec:
  replicas: 2
  selector:
    matchLabels:
      app: gateway
  template:
    metadata:
      labels:
        app: gateway
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - name: http-port
          containerPort: 8080
        - name: metrics-port
          containerPort: 9090
---
apiVersion: v1
kind: Service
metadata:
  name: multi-svc
  namespace: services-test
spec:
  type: ClusterIP
  selector:
    app: gateway
  ports:
  - name: http
    port: 80
    targetPort: http-port
  - name: metrics
    port: 9090
    targetPort: metrics-port

Commands:

# Apply manifest
kubectl apply -f solution4.yaml

# Verify both ports are exposed
kubectl get svc multi-svc -n services-test

# Test connectivity for both ports
kubectl run test --rm -it --image=busybox -n services-test -- wget -qO- multi-svc:80
kubectl run test --rm -it --image=busybox -n services-test -- wget -qO- multi-svc:9090

---

Solution 5: Multi-Protocol Service

Manifest:

apiVersion: v1
kind: Service
metadata:
  name: app-gateway
spec:
  selector:
    app: gateway
  ports:
  - name: tcp-web
    protocol: TCP
    port: 80
    targetPort: 8080
  - name: udp-dns
    protocol: UDP
    port: 53
    targetPort: 5353

---

Solution 6: Troubleshooting Selectors

Analysis: The issue is a mismatch between the Service selector and the Pod labels.

Fix: Ensure the Deployment pod template has the label tier: backend.

# Corrected Pod Template in Deployment
template:
  metadata:
    labels:
      app: myapp
      tier: backend  # Added this line

---

Solution 7: Service DNS & Resolution (CKA)

Commands:

# 1. Create namespaces
kubectl create ns alpha
kubectl create ns beta

# 2. Deploy in alpha
kubectl create deployment web --image=nginx --replicas=2 -n alpha
kubectl expose deployment web --name=alpha-svc --port=80 -n alpha

# 3. Test from beta namespace
kubectl run test --rm -it --image=busybox -n beta -- nslookup alpha-svc.alpha.svc.cluster.local

# 4. Verify connectivity with short and full FQDN
kubectl run test --rm -it --image=busybox -n beta -- wget -qO- alpha-svc.alpha:80
kubectl run test --rm -it --image=busybox -n beta -- wget -qO- alpha-svc.alpha.svc.cluster.local:80

Key Concepts:

• Same namespace: <service>
• Cross-namespace short: <service>.<namespace>
• Full FQDN: <service>.<namespace>.svc.cluster.local

---

Solution 8: Service Selectors & Endpoints (CKA)

Commands:

# 1. Create namespace
kubectl create ns testing

# 2. Create deployment
kubectl create deployment backend --image=nginx --replicas=2 -n testing
kubectl set labels deployment backend app=backend -n testing

# Alternative: Declarative approach
kubectl apply -f - <<EOF
apiVersion: apps/v1
kind: Deployment
metadata:
  name: backend
  namespace: testing
spec:
  replicas: 2
  selector:
    matchLabels:
      app: backend
  template:
    metadata:
      labels:
        app: backend
    spec:
      containers:
      - name: nginx
        image: nginx
---
apiVersion: v1
kind: Service
metadata:
  name: backend-svc
  namespace: testing
spec:
  selector:
    app: backend
  ports:
  - port: 80
EOF

# 3. Verify endpoints
kubectl get endpoints backend-svc -n testing
kubectl describe svc backend-svc -n testing

# 4. Test connectivity
kubectl run test --rm -it --image=busybox -n testing -- wget -qO- backend-svc:80

---

Solution 9: Manual Endpoints

Manifest:

apiVersion: v1
kind: Service
metadata:
  name: legacy-db
spec:
  ports:
  - port: 3306
---
apiVersion: v1
kind: Endpoints
metadata:
  name: legacy-db
subsets:
- addresses:
  - ip: 192.168.1.50
  ports:
  - port: 3306

---

Solution 10: Patching Service Types

Commands:

# 1. Create NodePort
kubectl create service nodeport upgrade-svc --tcp=80:80

# 2. Patch to ClusterIP (removing NodePort config)
# Note: Simply changing type to ClusterIP usually works, but explicit cleanup is cleaner
kubectl patch svc upgrade-svc -p '{"spec":{"type":"ClusterIP", "nodePort": null}}'