PLAN-configurable-service-names.md

Plan: Configurable Headless Service Names

Objective

Make headless service names configurable via environment variables across all Kubernetes manifests.

Tasks

1. Update Configuration System

• Verify current appsettings.json has ServiceName configuration
• Update appsettings.json to support env var fallback pattern
• Verify PodCoordinator.cs properly reads from IConfiguration

2. Add Environment Variables to Deployments

• Add SERVICE_NAME env var to all app deployments
• Ensure consistency with headless service names

3. Add Missing Headless Services

• Review which manifests need headless services
• Add headless services where missing
• Ensure naming consistency

4. Files to Update

Base Workloads (already have headless services)

• k8s/hpa/step-01-base-workload.yaml - Added SERVICE_NAME env var
• k8s/vpa/step-01-base-workload.yaml - Added SERVICE_NAME env var
• k8s/qos/step-01-guaranteed-qos.yaml - Added SERVICE_NAME and POD_NAMESPACE env vars
• k8s/combined/step-01-hpa-with-guaranteed-qos.yaml - Added SERVICE_NAME and POD_NAMESPACE env vars
• k8s/deployment.yaml - Added SERVICE_NAME env var

Need Headless Services Added

• k8s/combined/step-02-vpa-with-burstable-qos.yaml - Added backend-burstable-headless
• k8s/combined/step-03-complete-demo.yaml - Added 3 headless services
• k8s/qos/step-02-burstable-qos.yaml - Added burstable-qos-headless
• k8s/qos/step-03-besteffort-qos.yaml - Added besteffort-qos-headless
• k8s/qos/step-04-mixed-qos-eviction-demo.yaml - Added 3 headless services
• k8s/qos/step-05-priority-classes.yaml - Added 2 headless services

VPA Steps (reference base workload)

• Reference step-01-base-workload.yaml via VPA resources

Implementation Details

Environment Variable Pattern

env:
- name: SERVICE_NAME
  value: "k8s-demo-app-headless"

Headless Service Pattern

apiVersion: v1
kind: Service
metadata:
  name: k8s-demo-app-headless
  namespace: [appropriate-namespace]
spec:
  clusterIP: None
  selector:
    app: k8s-demo-app
  ports:
  - port: 80
    targetPort: 8080

Configuration Pattern

{
  "ServiceName": "k8s-demo-app-headless"
}

Validation

• All deployments with app containers have SERVICE_NAME env var
• All namespaces with deployments have corresponding headless services
• Service names match between env vars and service definitions
• PodCoordinator can discover pods via configurable service name