Hooks 生命周期

Hook 类型与执行时机

Hook 通过在 K8s 资源的 annotations 中添加 helm.sh/hook 来声明。Helm 在特定时间点执行这些资源，并等待它们完成后再继续。

helm upgrade 执行流程（含 Hooks）

  ① 渲染模板
       │
  ② 执行 pre-upgrade Hooks   ← 等待 Job/Pod 完成
       │
  ③ 更新 K8s 资源（apply）
       │
  ④ 等待资源 Ready
       │
  ⑤ 执行 post-upgrade Hooks  ← 等待 Job/Pod 完成
       │
  ⑥ 升级成功

Hook 权重：控制执行顺序

当同一时间点有多个 Hook 时，通过 helm.sh/hook-weight 控制执行顺序（从小到大，负数合法）。

# Hook 权重示例：先备份数据库，再运行迁移

--- backup-job.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: "{{ .Release.Name }}-backup"
  annotations:
    helm.sh/hook: pre-upgrade
    helm.sh/hook-weight: "-10"     # 权重越小越先执行
    helm.sh/hook-delete-policy: before-hook-creation
spec:
  template:
    spec:
      restartPolicy: Never
      containers:
      - name: backup
        image: postgres:15
        command: ["pg_dump", "-h", "$(DB_HOST)", "-U", "postgres", "-f", "/backup/dump.sql"]

--- migrate-job.yaml（权重 0，在 backup 之后执行）
annotations:
  helm.sh/hook: pre-upgrade
  helm.sh/hook-weight: "0"       # 权重 0，在 -10 之后执行
  helm.sh/hook-delete-policy: before-hook-creation

Hook 删除策略

# 同时使用多个删除策略（逗号分隔）
annotations:
  helm.sh/hook: pre-upgrade,pre-install      # 同一 Hook 可应用于多个时间点
  helm.sh/hook-weight: "5"
  helm.sh/hook-delete-policy: before-hook-creation,hook-succeeded

实战：数据库迁移 Job（pre-upgrade Hook）

# templates/hooks/db-migrate.yaml
apiVersion: batch/v1
kind: Job
metadata:
  name: "{{ include "myapp.fullname" . }}-db-migrate"
  namespace: {{ .Release.Namespace }}
  labels:
    {{- include "myapp.labels" . | nindent 4 }}
  annotations:
    "helm.sh/hook": pre-upgrade,pre-install
    "helm.sh/hook-weight": "0"
    "helm.sh/hook-delete-policy": before-hook-creation
spec:
  backoffLimit: 3
  template:
    metadata:
      labels:
        app.kubernetes.io/component: db-migrate
    spec:
      restartPolicy: Never
      initContainers:
      - name: wait-for-db             # 等待数据库就绪
        image: busybox:1.35
        command:
        - sh
        - -c
        - |
            until nc -z $DB_HOST $DB_PORT; do
              echo "Waiting for database..."; sleep 2
            done
            echo "Database is ready"
        env:
        - name: DB_HOST
          value: {{ .Values.database.host | quote }}
        - name: DB_PORT
          value: {{ .Values.database.port | quote }}
      containers:
      - name: migrate
        image: "{{ .Values.image.repository }}:{{ .Values.image.tag | default .Chart.AppVersion }}"
        command: ["python", "manage.py", "migrate"]
        env:
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: {{ include "myapp.fullname" . }}-secrets
              key: database-url

实战：Smoke Test（test Hook）

# templates/tests/test-connection.yaml
apiVersion: v1
kind: Pod
metadata:
  name: "{{ include "myapp.fullname" . }}-test-connection"
  annotations:
    "helm.sh/hook": test
    "helm.sh/hook-delete-policy": before-hook-creation
spec:
  restartPolicy: Never
  containers:
  - name: wget
    image: busybox:1.35
    command:
    - wget
    args:
    - "--spider"
    - "-T"
    - "10"
    - "http://{{ include "myapp.fullname" . }}:{{ .Values.service.port }}/health"

# 执行测试（helm test 命令）
helm test myapp

# 查看测试 Pod 的日志
helm test myapp --logs

# 带超时的测试
helm test myapp --timeout 5m

# 在 CI/CD 中使用（安装后立即测试）
helm upgrade --install myapp ./chart -f values-ci.yaml \
  --wait --timeout 5m
helm test myapp --timeout 3m