# Istio VirtualService + DestinationRule for blue/green traffic switching.
#
# Traffic flow:
#   Client → Istio Ingress Gateway → VirtualService → DestinationRule subset → Pod
#
# Two releases coexist at all times:
#   veylant-proxy-blue  (helm release, slot=blue label)
#   veylant-proxy-green (helm release, slot=green label)
#
# Switch traffic atomically (rollback < 5s):
#   # Switch to green:
#   kubectl patch vs veylant-proxy -n veylant --type merge \
#     -p '{"spec":{"http":[{"route":[{"destination":{"host":"veylant-proxy","subset":"green"},"weight":100}]}]}}'
#   # Roll back to blue:
#   kubectl patch vs veylant-proxy -n veylant --type merge \
#     -p '{"spec":{"http":[{"route":[{"destination":{"host":"veylant-proxy","subset":"blue"},"weight":100}]}]}}'
#
# Managed automatically by deploy/scripts/blue-green.sh.
---
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: veylant-proxy
  namespace: veylant
spec:
  hosts:
    - veylant-proxy
    - api.veylant.ai          # external hostname (TLS terminated at Gateway)
  gateways:
    - veylant-gateway
    - mesh                    # also applies to in-cluster traffic
  http:
    - match:
        - uri:
            prefix: /
      route:
        # Default: 100% to blue slot.
        # blue-green.sh patches this to switch slots atomically.
        - destination:
            host: veylant-proxy
            subset: blue
          weight: 100
      timeout: 35s             # slightly > proxy WriteTimeout (30s)
      retries:
        attempts: 2
        perTryTimeout: 15s
        retryOn: gateway-error,connect-failure,retriable-4xx
---
apiVersion: networking.istio.io/v1beta1
kind: DestinationRule
metadata:
  name: veylant-proxy
  namespace: veylant
spec:
  host: veylant-proxy
  trafficPolicy:
    connectionPool:
      http:
        h2UpgradePolicy: UPGRADE
        idleTimeout: 90s
    outlierDetection:
      consecutiveGatewayErrors: 5
      interval: 10s
      baseEjectionTime: 30s
  subsets:
    - name: blue
      labels:
        app.kubernetes.io/slot: blue
    - name: green
      labels:
        app.kubernetes.io/slot: green