Kubernetes Pod深入：多容器与生命周期

Pod设计模式

Sidecar模式

Sidecar容器与主容器共享网络和存储，提供辅助功能：

# sidecar-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: app-with-logging
spec:
  containers:
  - name: app
    image: myapp:1.0
    volumeMounts:
    - name: log-volume
      mountPath: /var/log/app
  - name: log-agent
    image: fluentd:latest
    volumeMounts:
    - name: log-volume
      mountPath: /var/log/app
    - name: fluentd-config
      mountPath: /fluentd/etc
  volumes:
  - name: log-volume
    emptyDir: {}
  - name: fluentd-config
    configMap:
      name: fluentd-config

Init Container

Init容器在主容器启动前运行：

# init-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: app-with-init
spec:
  initContainers:
  - name: init-db
    image: busybox:1.36
    command: ['sh', '-c', 'until nslookup mysql-service; do echo waiting for mysql; sleep 2; done']
  - name: init-config
    image: busybox:1.36
    command: ['sh', '-c', 'wget -O /config/app.yaml http://config-server/config']
    volumeMounts:
    - name: config-volume
      mountPath: /config
  containers:
  - name: app
    image: myapp:1.0
    volumeMounts:
    - name: config-volume
      mountPath: /config
  volumes:
  - name: config-volume
    emptyDir: {}

Pod生命周期

生命周期钩子

# lifecycle-pod.yaml
apiVersion: v1
kind: Pod
metadata:
  name: app-with-lifecycle
spec:
  containers:
  - name: app
    image: myapp:1.0
    lifecycle:
      postStart:
        exec:
          command: ["/bin/sh", "-c", "echo 'App started' > /var/log/lifecycle.log"]
      preStop:
        exec:
          command: ["/bin/sh", "-c", "nginx -s quit; sleep 5"]
    readinessProbe:
      httpGet:
        path: /health
        port: 8080
      initialDelaySeconds: 10
      periodSeconds: 5
    livenessProbe:
      httpGet:
        path: /health
        port: 8080
      initialDelaySeconds: 15
      periodSeconds: 10
    startupProbe:
      httpGet:
        path: /health
        port: 8080
      failureThreshold: 30
      periodSeconds: 10

探针类型

# 就绪探针（Readiness）
readinessProbe:
  httpGet:
    path: /ready
    port: 8080
  initialDelaySeconds: 5
  periodSeconds: 10
  successThreshold: 1
  failureThreshold: 3

# 存活探针（Liveness）
livenessProbe:
  tcpSocket:
    port: 8080
  initialDelaySeconds: 15
  periodSeconds: 20

# 启动探针（Startup）
startupProbe:
  exec:
    command:
    - cat
    - /tmp/healthy
  failureThreshold: 30
  periodSeconds: 10

Pod调度

节点选择器

apiVersion: v1
kind: Pod
metadata:
  name: gpu-pod
spec:
  nodeSelector:
    accelerator: nvidia-tesla-k80
  containers:
  - name: gpu-app
    image: myapp:gpu

亲和性

apiVersion: v1
kind: Pod
metadata:
  name: app-with-affinity
spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
        - matchExpressions:
          - key: zone
            operator: In
            values:
            - zone1
    podAntiAffinity:
      preferredDuringSchedulingIgnoredDuringExecution:
      - weight: 100
        podAffinityTerm:
          labelSelector:
            matchExpressions:
            - key: app
              operator: In
              values:
              - web
          topologyKey: kubernetes.io/hostname
  containers:
  - name: app
    image: myapp:1.0

污点与容忍

apiVersion: v1
kind: Pod
metadata:
  name: pod-with-toleration
spec:
  tolerations:
  - key: "dedicated"
    operator: "Equal"
    value: "special-user"
    effect: "NoSchedule"
  containers:
  - name: app
    image: myapp:1.0

资源管理

apiVersion: v1
kind: Pod
metadata:
  name: resource-pod
spec:
  containers:
  - name: app
    image: myapp:1.0
    resources:
      requests:
        memory: "256Mi"
        cpu: "500m"
        ephemeral-storage: "1Gi"
      limits:
        memory: "512Mi"
        cpu: "1000m"
        ephemeral-storage: "2Gi"

Pod模板示例

# 完整的Pod模板
apiVersion: v1
kind: Pod
metadata:
  name: production-app
  labels:
    app: myapp
    version: v1
    environment: production
spec:
  restartPolicy: Always
  terminationGracePeriodSeconds: 30
  containers:
  - name: app
    image: myapp:1.0:latest
    ports:
    - containerPort: 8080
      name: http
    env:
    - name: APP_ENV
      value: "production"
    - name: DB_PASSWORD
      valueFrom:
        secretKeyRef:
          name: db-secret
          key: password
    volumeMounts:
    - name: config
      mountPath: /app/config
    resources:
      requests:
        memory: "256Mi"
        cpu: "250m"
      limits:
        memory: "512Mi"
        cpu: "500m"
  volumes:
  - name: config
    configMap:
      name: app-config

调试技巧

# 查看Pod状态
kubectl get pods -o wide
kubectl get pods -o yaml

# 查看Pod日志
kubectl logs <pod-name>
kubectl logs <pod-name> -c <container-name>
kubectl logs <pod-name> --previous

# 进入Pod
kubectl exec -it <pod-name> -- sh
kubectl exec -it <pod-name> -c <container-name> -- sh

# 端口转发
kubectl port-forward <pod-name> 8080:80

总结

Pod是Kubernetes中最核心的概念。理解Pod的设计模式、生命周期和调度策略，是编写高质量Kubernetes应用的基础。