# 08-keda-event-driven — Kafka-lag-driven scaling on a Deployment, VPA orthogonal.

integrations:
  monitoring:
    defaults:
      enabled: true
      provider: prometheus
      discovery: crd
      type: service
      exposeService:
        enabled: true                 # auto metrics-only Service for service-less workloads
        port: 9090
        targetPort: 9090

deployments:

  worker:
    enabled: true
    image:
      repository: ghcr.io/example/orders-worker
      tag: v0.9.0
      pullPolicy: IfNotPresent

    service:
      enabled: false                  # no inbound traffic; metrics-only Service auto-emitted

    metrics:
      enabled: true
      type: pod                       # PodMonitor scrapes pod IPs directly

    keda:
      enabled: true
      minReplicas: 1
      maxReplicas: 30
      pollingInterval: 30             # seconds between metric polls
      cooldownPeriod: 300             # seconds without load before scaling to min
      triggers:
        - type: kafka
          metadata:
            bootstrapServers: kafka.kafka:9092
            consumerGroup: orders-worker
            topic: orders
            lagThreshold: "100"       # one replica per 100 messages of lag
            offsetResetPolicy: earliest
      # Tames the HPA that KEDA creates. Passed through verbatim.
      advanced:
        restoreToOriginalReplicaCount: true
        horizontalPodAutoscalerConfig:
          behavior:
            # One pod a minute up; the HPA default doubles every 15s.
            scaleUp:
              stabilizationWindowSeconds: 60
              policies:
                - type: Pods
                  value: 1
                  periodSeconds: 60
            # 15 minutes of quiet before giving a replica back.
            scaleDown:
              stabilizationWindowSeconds: 900
              policies:
                - type: Pods
                  value: 1
                  periodSeconds: 300

    # VPA is orthogonal to KEDA — VPA touches resources.requests, KEDA touches replicas.
    # Initial mode applies the recommendation only on pod creation; it doesn't evict.
    verticalPodAutoscaler:
      enabled: true
      updateMode: Initial
      resourcePolicy:
        containerPolicies:
          - containerName: "*"
            minAllowed:
              cpu: 50m
              memory: 128Mi
            maxAllowed:
              cpu: "2"
              memory: 1Gi

    env:
      LOG_LEVEL:
        value: info

    resources:
      requests:
        cpu: 100m
        memory: 256Mi
      limits:
        memory: 512Mi

# A modest PDB so KEDA's scale-down doesn't take everything at once.
podDisruptionBudget:
  enabled: true
  minAvailable: 1