What is Kubernetes Service Topology?

Question

Accepted Answer

**Topology** — route traffic based on node/zone topology.

```yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp
spec:
  type: ClusterIP
  selector:
    app: myapp
  ports:
  - port: 80
    targetPort: 3000
  topologyKeys:
  - topology.kubernetes.io/zone
  - kubernetes.io/hostname
  - "*"
---
# TopologyAwareHints (preferred)
apiVersion: v1
kind: Service
metadata:
  name: myapp-hints
  annotations:
    service.kubernetes.io/topology-mode: Auto
spec:
  type: ClusterIP
  selector:
    app: myapp
  ports:
  - port: 80
    targetPort: 3000
  internalTrafficPolicy: Local
---
apiVersion: v1
kind: Endpoints
metadata:
  name: myapp-hints
subsets:
- addresses:
  - ip: 10.0.1.5
    nodeName: node-1
    zone: us-west-2a
  - ip: 10.0.2.8
    nodeName: node-2
    zone: us-west-2b
  ports:
  - port: 3000
```

```bash
# Check topology hints
kubectl get endpoints myapp-hints -o yaml | grep hints

# Verify node zones
kubectl get nodes -o custom-columns=NAME:.metadata.name,ZONE:.metadata.labels.topology\.kubernetes\.io/zone

# Check internal traffic policy
kubectl get svc myapp-hints -o jsonpath='{.spec.internalTrafficPolicy}'
```

**Options:**
- topologyKeys: prefer specific topology level.
- TopologyAwareHints: automatic zone routing.
- internalTrafficPolicy: Local or Cluster.

**Benefits:**
- Reduce cross-zone traffic.
- Lower latency.
- Cost optimization.

DevOps: What is Kubernetes Service Topology?