Note_Tech

All technological notes.

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Argo Rollout - Traffic-Weighted Canary

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• Argo Rollout - Traffic-Weighted Canary
  • Header-based routing
  • Lab: Header-based routing
    • Deploy Stable Version
    • Deploy Preview Version

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Header-based routing

• Header-based routing
  • direct specific HTTP requests to a canary version of the application based on request headers, rather than a random percentage of traffic.
  • useful for A/B testing, session stickiness, or allowing internal testers to preview a new version by adding a specific header (e.g., x-canary: true).
• How it Works
  • header-based routing uses the setHeaderRoute action within the rollout steps.
  • When a request matches the specified header criteria, the traffic router (like Istio or Nginx) bypasses the weighted logic and sends that traffic directly to the canary service.

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Lab: Header-based routing

Deploy Stable Version

# 00-namespace.yaml
apiVersion: v1
kind: Namespace
metadata:
  name: gtw-canary
---
# 01-gateway.yaml
apiVersion: gateway.networking.k8s.io/v1
kind: Gateway
metadata:
  name: rollout-gtw
  namespace: gtw-canary
spec:
  gatewayClassName: traefik
  listeners:
    - name: http
      protocol: HTTP
      port: 80
      allowedRoutes:
        namespaces:
          from: Same
---
# 02-httproute.yaml
apiVersion: gateway.networking.k8s.io/v1
kind: HTTPRoute
metadata:
  name: rollout-gtw-route
  namespace: gtw-canary
spec:
  parentRefs:
    - name: rollout-gtw
  hostnames:
    - "app.localhost"
  rules:
    - backendRefs:
        - name: rollout-gtw-stable
          port: 80
          weight: 1
        - name: rollout-gtw-canary
          port: 80
          weight: 1
---
# 03-services.yaml
apiVersion: v1
kind: Service
metadata:
  name: rollout-gtw-stable
  namespace: gtw-canary
spec:
  ports:
    - name: http
      port: 80
      targetPort: 80
      protocol: TCP
  selector:
    app: rollout-gtw
---
apiVersion: v1
kind: Service
metadata:
  name: rollout-gtw-canary
  namespace: gtw-canary
spec:
  ports:
    - name: http
      port: 80
      targetPort: 80
      protocol: TCP
  selector:
    app: rollout-gtw
---
# 04-rollout.yaml
apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: rollout-gtw
  namespace: gtw-canary
spec:
  replicas: 5
  selector:
    matchLabels:
      app: rollout-gtw
  template:
    metadata:
      labels:
        app: rollout-gtw
    spec:
      containers:
        - name: rollout-gtw
          image: argoproj/rollouts-demo:yellow
          # image: argoproj/rollouts-demo:red
          ports:
            - name: http
              containerPort: 80
              protocol: TCP
  strategy:
    canary:
      dynamicStableScale: true
      canaryService: rollout-gtw-canary
      stableService: rollout-gtw-stable
      trafficRouting:
        managedRoutes:
          - name: qa-override
        plugins:
          argoproj-labs/gatewayAPI:
            httpRoute: rollout-gtw-route
            namespace: gtw-canary
      steps:
        - setWeight: 1 # set traffic %
        - pause:
            duration: 20s
        - setCanaryScale: # set pod %
            weight: 40
        - setHeaderRoute:
            name: qa-override
            match:
              - headerName: x-canary
                headerValue:
                  exact: "true"
        - pause: {}
        - setWeight: 30
        - pause: {}
        - setWeight: 40
        - pause:
            duration: 10s
        - setWeight: 60
        - pause:
            duration: 10s
        - setWeight: 80
        - pause:
            duration: 10s

kubectl apply -f .
# namespace/gtw-canary unchanged
# gateway.gateway.networking.k8s.io/rollout-gtw unchanged
# httproute.gateway.networking.k8s.io/rollout-gtw-route configured
# service/rollout-gtw-stable unchanged
# service/rollout-gtw-canary unchanged
# rollout.argoproj.io/rollout-gtw created

Deploy Preview Version

# confirm pod scale 40%
kubectl argo rollouts get rollout rollout-gtw -n gtw-canary
# Name:            rollout-gtw
# Namespace:       gtw-canary
# Status:          ॥ Paused
# Message:         CanaryPauseStep
# Strategy:        Canary
#   Step:          4/13
#   SetWeight:     1
#   ActualWeight:  1
# Images:          argoproj/rollouts-demo:red (canary)
#                  argoproj/rollouts-demo:yellow (stable)
# Replicas:
#   Desired:       5
#   Current:       7
#   Updated:       2
#   Ready:         7
#   Available:     7

# NAME                                     KIND        STATUS     AGE    INFO
# ⟳ rollout-gtw                            Rollout     ॥ Paused   7m
# ├──# revision:2
# │  └──⧉ rollout-gtw-78558b664b           ReplicaSet  ✔ Healthy  2m38s  canary
# │     ├──□ rollout-gtw-78558b664b-d98z9  Pod         ✔ Running  2m38s  ready:1/1
# │     └──□ rollout-gtw-78558b664b-q6g89  Pod         ✔ Running  2m17s  ready:1/1
# └──# revision:1
#    └──⧉ rollout-gtw-79d56bbcd5           ReplicaSet  ✔ Healthy  7m     stable
#       ├──□ rollout-gtw-79d56bbcd5-4xsq7  Pod         ✔ Running  7m     ready:1/1
#       ├──□ rollout-gtw-79d56bbcd5-p2572  Pod         ✔ Running  7m     ready:1/1
#       ├──□ rollout-gtw-79d56bbcd5-p8j4v  Pod         ✔ Running  7m     ready:1/1
#       ├──□ rollout-gtw-79d56bbcd5-vzxb2  Pod         ✔ Running  7m     ready:1/1
#       └──□ rollout-gtw-79d56bbcd5-zlmm4  Pod         ✔ Running  7m     ready:1/1

# confirm traffic 1%; header
kubectl describe httproute -n gtw-canary rollout-gtw-route
  # Rules:
  #   Backend Refs:
  #     Group:
  #     Kind:    Service
  #     Name:    rollout-gtw-stable
  #     Port:    80
  #     Weight:  99
  #     Group:
  #     Kind:    Service
  #     Name:    rollout-gtw-canary
  #     Port:    80
  #     Weight:  1
  #   Backend Refs:
  #     Group:
  #     Kind:    Service
  #     Name:    rollout-gtw-canary
  #     Port:    80
  #     Weight:  1
  #   Matches:
  #     Headers:
  #       Name:   x-canary
  #       Type:   Exact
  #       Value:  true
  #     Path:
  #       Type:   PathPrefix
  #       Value:  /
  #   Name:       qa-override