发布策略与渐进式交付

spec:
  replicas: 10
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxUnavailable: 25%     # 更新过程中最多允许几个副本不可用
      maxSurge: 25%           # 更新过程中最多允许超出期望副本数几个

发布前：  用户 ──> Service ──> 绿 Pod（v1.2）
发布中：  蓝 Pod（v1.3）部署完成，冒烟验证
切换后：  用户 ──> Service ──> 蓝 Pod（v1.3）     绿保留，随时切回

apiVersion: v1
kind: Service
metadata:
  name: web
spec:
  selector:
    version: green        # 切换 = 把这一行改成 blue（kubectl patch 或改清单）
  ports:
    - port: 80
      targetPort: 8080

apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: web
spec:
  replicas: 10
  strategy:
    canary:
      canaryService: web-canary        # 指向新版本的 Service
      stableService: web-stable
      trafficRouting:
        nginx:
          stableIngress: web-ingress   # 由 Ingress 层做比例切分
      steps:
        - setWeight: 5
        - pause: { duration: 10m }     # 人工或指标把关的观察期
        - analysis:                    # 指标分析：不达标自动中止回滚
            templates:
              - templateName: error-rate-check
        - setWeight: 30
        - pause: { duration: 10m }
        - setWeight: 100

apiVersion: argoproj.io/v1alpha1
kind: AnalysisTemplate
metadata:
  name: error-rate-check
spec:
  metrics:
    - name: http-error-rate
      interval: 1m
      failureLimit: 2                 # 连续 2 次采样超标即失败
      successCondition: result[0] < 0.01
      provider:
        prometheus:
          address: http://prometheus:9090
          query: |
            sum(rate(http_requests_total{version="canary",code=~"5.."}[2m]))
            / sum(rate(http_requests_total{version="canary"}[2m]))

1. Expand：加新列 name_full，写入双写（新旧两列都写），发布 v2 代码（只读新列）
2. Migrate：后台把存量数据从 name 拷到 name_full，校验一致性
3. Contract：确认 v1 彻底退役后，下一个版本删掉旧列与双写逻辑

apiVersion: argoproj.io/v1alpha1
kind: Rollout
metadata:
  name: myapp
spec:
  replicas: 10
  strategy:
    canary:
      steps:                       # 放量台阶：停够时间才继续
        - setWeight: 10
        - pause: { duration: 5m }
        - setWeight: 30
        - pause: { duration: 5m }
        - setWeight: 50
        - pause: { duration: 5m }
        - setWeight: 80
        - pause: { duration: 5m }
      canaryService: myapp-canary
      stableService: myapp-stable
      trafficRouting:              # 流量精确切分交给网格
        istio:
          virtualServices:
            - name: myapp-vsvc
              routes: [primary]
      analysis:                    # 每个台阶自动做指标验证
        templates:
          - templateName: success-rate
        args:
          - name: service-name
            value: myapp-canary
---
apiVersion: argoproj.io/v1alpha1
kind: AnalysisTemplate
metadata:
  name: success-rate
spec:
  args: [{ name: service-name }]
  metrics:
    - name: success-rate
      provider:
        prometheus:
          address: http://prometheus:9090
          query: |
            sum(rate(http_requests_total{service="{{args.service-name}}",status!~"5.."}[5m]))
            /
            sum(rate(http_requests_total{service="{{args.service-name}}"}[5m]))
      successCondition: result[0] >= 0.99   # 成功率跌破 99% 自动中止回滚
      interval: 30s
      count: 10

apiVersion: flagger.app/v1beta1
kind: Canary
metadata:
  name: myapp
spec:
  targetRef:
    apiVersion: apps/v1
    kind: Deployment
    name: myapp
  service:
    port: 8080
  analysis:
    interval: 1m
    threshold: 5            # 连续失败 5 次才回滚
    maxWeight: 50           # 金丝雀最多吃到 50% 流量
    stepWeight: 10          # 每分钟加 10%
    metrics:
      - name: request-success-rate
        thresholdRange: { min: 99 }
        interval: 1m
      - name: request-duration
        thresholdRange: { max: 500 }   # 延迟 500ms 红线
        interval: 1m
    webhooks:
      - name: load-test
        url: http://flagger-loadtester/
        timeout: 5s
        metadata:
          cmd: 'hey -z 1m -q 10 -c 2 http://myapp:8080/'

kubectl patch svc web -p '{"spec":{"selector":{"version":"blue"}}}'
kubectl get endpoints web -w        # 观察切换前后 Endpoints 变化
# 回滚就是把 version 改回 green——这就是「秒级」的来源

kubectl set image deployment/web nginx=nginx:does-not-exist
kubectl get pods -w                  # 对比新旧副本数量变化
kubectl rollout undo deployment/web  # 实验结束回滚