Kubernetes核心资源

1. Pod

1.1 Pod 概念

Pod 是 Kubernetes 最小调度单元，包含一个或多个容器，共享网络和存储。

1.2 Pod 生命周期

1.3 Pod 配置

apiVersion: v1
kind: Pod
metadata:
  name: web-app
spec:
  containers:
    - name: app
      image: nginx:1.25
      ports:
        - containerPort: 80
      resources:
        requests:
          cpu: 100m
          memory: 128Mi
        limits:
          cpu: 500m
          memory: 512Mi
      livenessProbe:
        httpGet:
          path: /healthz
          port: 80
        initialDelaySeconds: 15
        periodSeconds: 10
      readinessProbe:
        httpGet:
          path: /ready
          port: 80
        initialDelaySeconds: 5
        periodSeconds: 5
      env:
        - name: DB_HOST
          valueFrom:
            configMapKeyRef:
              name: app-config
              key: database_host
      volumeMounts:
        - name: data
          mountPath: /data
  volumes:
    - name: data
      persistentVolumeClaim:
        claimName: app-data

1.4 探针类型

2. Deployment

2.1 概念

管理无状态应用，维护 Pod 副本数和滚动更新。

2.2 配置示例

apiVersion: apps/v1
kind: Deployment
metadata:
  name: web-deployment
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 0
  selector:
    matchLabels:
      app: web
  template:
    metadata:
      labels:
        app: web
    spec:
      containers:
        - name: web
          image: nginx:1.25
          ports:
            - containerPort: 80

2.3 更新策略

2.4 常用操作

# 查看滚动更新状态
kubectl rollout status deployment/web

# 查看历史版本
kubectl rollout history deployment/web

# 回滚
kubectl rollout undo deployment/web

# 回滚到指定版本
kubectl rollout undo deployment/web --to-revision=2

# 暂停/恢复更新
kubectl rollout pause deployment/web
kubectl rollout resume deployment/web

3. Service

3.1 概念

Service 为一组 Pod 提供稳定的访问入口和负载均衡。

3.2 Service 类型

3.3 配置示例

apiVersion: v1
kind: Service
metadata:
  name: web-service
spec:
  type: ClusterIP
  selector:
    app: web
  ports:
    - port: 80
      targetPort: 8080

3.4 服务发现

# 集群内访问
web-service.default.svc.cluster.local

# 简写（同命名空间）
web-service

4. StatefulSet

4.1 概念

管理有状态应用，提供稳定的网络标识和持久化存储。

4.2 与 Deployment 区别

4.3 配置示例

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: mysql
spec:
  serviceName: mysql
  replicas: 3
  selector:
    matchLabels:
      app: mysql
  template:
    metadata:
      labels:
        app: mysql
    spec:
      containers:
        - name: mysql
          image: mysql:8.0
          volumeMounts:
            - name: data
              mountPath: /var/lib/mysql
  volumeClaimTemplates:
    - metadata:
        name: data
      spec:
        accessModes: ['ReadWriteOnce']
        resources:
          requests:
            storage: 10Gi

5. ConfigMap 与 Secret

5.1 ConfigMap

apiVersion: v1
kind: ConfigMap
metadata:
  name: app-config
data:
  database_host: 'mysql.default.svc.cluster.local'
  database_port: '3306'
  app.properties: |
    key1=value1
    key2=value2

5.2 Secret

apiVersion: v1
kind: Secret
metadata:
  name: db-secret
type: Opaque
data:
  username: YWRtaW4= # base64(admin)
  password: cGFzc3dvcmQ= # base64(password)

注意：Secret 默认仅 Base64 编码，建议启用加密存储或使用外部密钥管理（Vault）。

6. DaemonSet 与 Job

6.1 DaemonSet

每个节点运行一个 Pod 副本，适用于日志采集、监控代理等。

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: fluentd
spec:
  selector:
    matchLabels:
      app: fluentd
  template:
    metadata:
      labels:
        app: fluentd
    spec:
      containers:
        - name: fluentd
          image: fluentd:latest

6.2 Job 与 CronJob

# 一次性任务
apiVersion: batch/v1
kind: Job
metadata:
  name: data-migration
spec:
  completions: 1
  backoffLimit: 3
  template:
    spec:
      containers:
        - name: migrate
          image: myapp:migrate
      restartPolicy: Never

# 定时任务
apiVersion: batch/v1
kind: CronJob
metadata:
  name: daily-backup
spec:
  schedule: '0 2 * * *'
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: backup
              image: myapp:backup
          restartPolicy: OnFailure