Progressive Delivery with Flagger: Automated Canary Deployments

Manual canary deployments are tedious. Flagger automates the entire process: deploy canary, shift traffic gradually, analyze metrics, promote or rollback automatically.

TL;DR

• Flagger = automated canary/blue-green/A-B testing
• Metrics-based promotion (Prometheus, Datadog, etc.)
• Automatic rollback on failure
• Works with Istio, Linkerd, Nginx, Gateway API
• Full GitOps integration

Install Flagger

helm repo add flagger https://flagger.app
helm upgrade -i flagger flagger/flagger \
  --namespace flagger-system --create-namespace \
  --set meshProvider=istio \
  --set metricsServer=http://prometheus.monitoring:9090

Canary Resource

apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  name: api-server
  namespace: production
spec:
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: api-server
  
  progressDeadlineSeconds: 600
  
  service:
    port: 8080
    targetPort: 8080
    gateways:
      - production-gateway
    hosts:
      - api.company.com
  
  analysis:
    # Canary increment
    interval: 1m
    threshold: 5
    maxWeight: 50
    stepWeight: 10
    
    # Promotion metrics
    metrics:
      - name: request-success-rate
        thresholdRange:
          min: 99
        interval: 1m
      
      - name: request-duration
        thresholdRange:
          max: 500
        interval: 1m
    
    # Webhooks for custom checks
    webhooks:
      - name: load-test
        type: rollout
        url: http://loadtester.flagger-system/
        metadata:
          cmd: "hey -z 1m -q 10 -c 2 http://api-server-canary.production:8080/"

Metrics Templates

apiVersion: flagger.app/v1beta1
kind: MetricTemplate
metadata:
  name: request-success-rate
  namespace: flagger-system
spec:
  provider:
    type: prometheus
    address: http://prometheus.monitoring:9090
  query: |
    100 - (
      sum(
        rate(
          http_requests_total{
            namespace="{{ namespace }}",
            service=~"{{ target }}-canary",
            status=~"5.."
          }[{{ interval }}]
        )
      ) 
      / 
      sum(
        rate(
          http_requests_total{
            namespace="{{ namespace }}",
            service=~"{{ target }}-canary"
          }[{{ interval }}]
        )
      ) * 100
    )

---
apiVersion: flagger.app/v1beta1
kind: MetricTemplate
metadata:
  name: request-duration
  namespace: flagger-system
spec:
  provider:
    type: prometheus
    address: http://prometheus.monitoring:9090
  query: |
    histogram_quantile(0.99,
      sum(
        rate(
          http_request_duration_seconds_bucket{
            namespace="{{ namespace }}",
            service=~"{{ target }}-canary"
          }[{{ interval }}]
        )
      ) by (le)
    ) * 1000

Blue-Green Deployment

apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  name: api-server
  namespace: production
spec:
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: api-server
  
  service:
    port: 8080
  
  analysis:
    # Blue-green: 0% or 100%
    interval: 1m
    threshold: 5
    iterations: 10  # Run analysis 10 times before promoting
    
    metrics:
      - name: request-success-rate
        thresholdRange:
          min: 99
        interval: 1m
    
    webhooks:
      - name: acceptance-test
        type: pre-rollout
        url: http://loadtester.flagger-system/
        metadata:
          type: bash
          cmd: "curl -s http://api-server-canary.production:8080/health | grep ok"
      
      - name: load-test
        type: rollout
        url: http://loadtester.flagger-system/
        metadata:
          cmd: "hey -z 2m -q 50 -c 10 http://api-server-canary.production:8080/"

A/B Testing

apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  name: api-server
  namespace: production
spec:
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: api-server
  
  service:
    port: 8080
  
  analysis:
    interval: 1m
    threshold: 5
    iterations: 100
    
    # A/B testing by header
    match:
      - headers:
          x-user-type:
            exact: beta
    
    metrics:
      - name: request-success-rate
        thresholdRange:
          min: 99
        interval: 1m

Gateway API Integration

apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  name: api-server
  namespace: production
spec:
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: api-server
  
  service:
    port: 8080
  
  # Use Gateway API instead of Istio
  gatewayRefs:
    - name: production-gateway
      namespace: gateway-system
  
  analysis:
    interval: 1m
    threshold: 5
    maxWeight: 50
    stepWeight: 10
    
    metrics:
      - name: request-success-rate
        templateRef:
          name: request-success-rate
          namespace: flagger-system
        thresholdRange:
          min: 99

Alerting

apiVersion: flagger.app/v1beta1
kind: AlertProvider
metadata:
  name: slack
  namespace: flagger-system
spec:
  type: slack
  channel: deployments
  username: flagger
  secretRef:
    name: slack-url

---
apiVersion: v1
kind: Secret
metadata:
  name: slack-url
  namespace: flagger-system
stringData:
  address: https://hooks.slack.com/services/xxx/yyy/zzz

GitOps Workflow

# Argo CD triggers Flagger
apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  name: api-server
  namespace: argocd
spec:
  source:
    repoURL: https://github.com/company/app
    path: k8s
    targetRevision: HEAD
  destination:
    server: https://kubernetes.default.svc
    namespace: production
  syncPolicy:
    automated:
      prune: true
      selfHeal: true

# Deployment update triggers Flagger canary
# Flagger handles the progressive rollout

Monitoring Progress

# Watch canary status
kubectl get canary -n production -w

# Describe canary
kubectl describe canary api-server -n production

# Check events
kubectl get events -n production --field-selector involvedObject.name=api-server

Rollback

# Manual rollback
kubectl annotate canary api-server -n production flagger.app/rollback=true

# Or set status
kubectl patch canary api-server -n production \
  --type=merge -p '{"status":{"phase":"Failed"}}'

References

• Flagger Docs: https://docs.flagger.app
• Metrics: https://docs.flagger.app/usage/metrics
• Webhooks: https://docs.flagger.app/usage/webhooks

======================================== Flagger + Progressive Delivery

Deploy with confidence. Rollback automatically.