What is Progressive Delivery?

Question

Accepted Answer

**Progressive Delivery** — gradual delivery of changes with automatic feedback.

**Stages:**
1. **Deploy** — new code in staging.
2. **Canary** — 5% traffic to production.
3. **Analysis** — monitoring metrics (errors, latency).
4. **Promote** — increase to 100%.
5. **Rollback** — on anomalies.

**Tools:** Argo Rollouts, Flagger, Flagger + Istio/Cilium.

**Flagger + Istio:**
```yaml
apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  name: myapp
  namespace: production
spec:
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: myapp
  service:
    port: 8080
    targetPort: 8080
  analysis:
    interval: 1m
    threshold: 5
    maxWeight: 50
    stepWeight: 10
    metrics:
      - name: request-success-rate
        thresholdRange:
          min: 99
        interval: 1m
      - name: request-duration
        thresholdRange:
          max: 500
        interval: 30s
    webhooks:
      - name: load-test
        type: rollout
        url: http://flagger-loadtester.test/
        metadata:
          cmd: "hey -z 1m -q 10 -c 2 http://myapp-canary:8080/"
```

**Flagger + Cilium (without Istio):**
```yaml
spec:
  service:
    port: 8080
  analysis:
    metrics:
      - name: request-success-rate
```
Flagger uses Cilium TrafficSplit for routing.

**Automatic Rollback:** if metrics fail analysis 5 times → rollback.

DevOps: What is Progressive Delivery?