What is Kubernetes LoadBalancer Service?

Question

Accepted Answer

**LoadBalancer** — expose Service externally via cloud load balancer.

```yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp-lb
  annotations:
    # AWS NLB
    service.beta.kubernetes.io/aws-load-balancer-type: "nlb"
    service.beta.kubernetes.io/aws-load-balancer-cross-zone-load-balancing-enabled: "true"
    service.beta.kubernetes.io/aws-load-balancer-scheme: "internet-facing"
    # GCP
    cloud.google.com/neg: '{"ingress": true}'
    # Azure
    service.beta.kubernetes.io/azure-load-balancer-resource-group: "my-rg"
spec:
  type: LoadBalancer
  selector:
    app: myapp
  ports:
  - name: http
    port: 80
    targetPort: 3000
    protocol: TCP
  - name: https
    port: 443
    targetPort: 3000
    protocol: TCP
  loadBalancerSourceRanges:
  - 10.0.0.0/8
  - 192.168.0.0/16
  externalTrafficPolicy: Local
  sessionAffinity: ClientIP
  sessionAffinityConfig:
    clientIP:
      timeoutSeconds: 10800
```

```bash
# Commands
kubectl get svc myapp-lb
kubectl describe svc myapp-lb

# Check external IP
kubectl get svc myapp-lb -o jsonpath='{.status.loadBalancer.ingress[0].ip}'
kubectl get svc myapp-lb -o jsonpath='{.status.loadBalancer.ingress[0].hostname}'

# Cloud-specific commands
aws elb describe-load-balancers | grep myapp
gcloud compute forwarding-rules list | grep myapp
az network lb list | grep myapp

# Wait for external IP
kubectl wait --for=condition=LoadBalancer svc/myapp-lb --timeout=300s
```

**External Traffic Policy:**
- Cluster: distribute across all nodes.
- Local: only nodes with Pod (preserves source IP).

**Load Balancer Types:**
- AWS: NLB (TCP) or ALB (HTTP).
- GCP: Network LB or HTTP(S) LB.
- Azure: Standard LB.

DevOps: What is Kubernetes LoadBalancer Service?