firstgold/.agents/skills/devops-engineer/references/deployment-strategies.md

Deployment Strategies

Strategy Comparison

Strategy	Use When	Rollback	Risk
Rolling	Standard updates, can tolerate mixed versions	Automatic via health checks	Low
Blue-Green	Zero downtime, instant rollback needed	Switch traffic to old env	Medium
Canary	Risk mitigation, gradual rollout	Scale down canary	Low
Recreate	Stateful apps, breaking changes	Redeploy previous version	High

Rolling Deployment (Kubernetes)

apiVersion: apps/v1
kind: Deployment
spec:
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 25%        # Max pods above desired
      maxUnavailable: 25%  # Max pods unavailable

Blue-Green with Ingress

# Blue deployment (current)
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-blue
  labels:
    version: blue
---
# Green deployment (new)
apiVersion: apps/v1
kind: Deployment
metadata:
  name: app-green
  labels:
    version: green
---
# Service pointing to active version
apiVersion: v1
kind: Service
metadata:
  name: app
spec:
  selector:
    version: blue  # Switch to 'green' for cutover

Canary with Istio

apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: app
spec:
  hosts:
    - app
  http:
    - match:
        - headers:
            canary:
              exact: "true"
      route:
        - destination:
            host: app-canary
    - route:
        - destination:
            host: app-stable
          weight: 90
        - destination:
            host: app-canary
          weight: 10

Rollback Procedures

Kubernetes Rollback

# View rollout history
kubectl rollout history deployment/app

# Rollback to previous
kubectl rollout undo deployment/app

# Rollback to specific revision
kubectl rollout undo deployment/app --to-revision=2

# Check status
kubectl rollout status deployment/app

ArgoCD Rollback

argocd app rollback app-prod --revision=123

Terraform Rollback

# Identify previous state
terraform state list

# Import previous configuration
git checkout HEAD~1 -- main.tf
terraform apply

Pre-deployment Checklist

• Database migrations are backward compatible
• Feature flags for new functionality
• Monitoring dashboards updated
• Alert thresholds reviewed
• Rollback procedure documented
• Staging tested and approved
• Team notified of deployment window

Post-deployment Verification

# Check pod status
kubectl get pods -l app=app

# Check logs for errors
kubectl logs -l app=app --tail=100 | grep -i error

# Verify endpoints
curl -f https://app.example.com/health

# Check metrics
# - Error rate < 1%
# - Latency p99 < 500ms
# - No memory/CPU spikes

Deployment Metrics (DORA)

Track four key metrics:

• Deployment Frequency: Target 10+/day
• Lead Time for Changes: Target <1 hour
• Change Failure Rate: Target <5%
• MTTR: Target <30 minutes

# Prometheus metrics for DORA tracking
- record: deployment:frequency:1d
  expr: count_over_time(deployment_completed[1d])

- record: deployment:lead_time:p95
  expr: histogram_quantile(0.95,
    rate(commit_to_deploy_seconds_bucket[1h]))

- record: deployment:failure_rate
  expr: |
    sum(rate(deployment_failed[1h]))
    / sum(rate(deployment_total[1h]))

Advanced Canary with Automated Analysis

# Flagger: Automated canary with rollback
apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  name: api
spec:
  provider: istio
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: api
  progressDeadlineSeconds: 60
  service:
    port: 8080
    trafficPolicy:
      tls:
        mode: ISTIO_MUTUAL
  analysis:
    interval: 30s
    threshold: 5
    maxWeight: 50
    stepWeight: 10
    metrics:
      - name: error-rate
        templateRef:
          name: error-rate
        thresholdRange:
          max: 1
      - name: latency
        templateRef:
          name: latency
        thresholdRange:
          max: 500
    webhooks:
      - name: acceptance-test
        type: pre-rollout
        url: http://test-runner/
      - name: load-test
        url: http://loadtester/
        timeout: 5s
        metadata:
          type: bash
          cmd: "hey -z 1m -q 10 http://api-canary:8080/"

Shadow Deployment

# Mirror traffic to shadow deployment
apiVersion: networking.istio.io/v1beta1
kind: VirtualService
metadata:
  name: api
spec:
  hosts:
    - api
  http:
    - match:
        - headers:
            x-test-version:
              exact: "v2"
      route:
        - destination:
            host: api
            subset: v2
      mirror:
        host: api
        subset: v2-shadow
      mirrorPercentage:
        value: 100
    - route:
        - destination:
            host: api
            subset: v1