Kubernetes Pod详解

Pod概念

Pod是Kubernetes中最小的可部署单元，是一组共享网络和存储的容器。

Pod生命周期

Pending → Running → Succeeded/Failed
    ↓
  等待调度  运行中    完成/失败

Pod状态

状态	说明
Pending	等待调度或拉取镜像
Running	至少一个容器运行中
Succeeded	所有容器成功退出
Failed	至少一个容器失败
Unknown	状态未知

Pod配置详解

apiVersion: v1
kind: Pod
metadata:
  name: myapp
  labels:
    app: myapp
    env: production
spec:
  # 容器配置
  containers:
    - name: myapp
      image: myapp:v1
      ports:
        - containerPort: 8080
          protocol: TCP
      
      # 资源限制
      resources:
        requests:
          cpu: "100m"
          memory: "128Mi"
        limits:
          cpu: "500m"
          memory: "512Mi"
      
      # 环境变量
      env:
        - name: DB_HOST
          value: "mysql-service"
        - name: DB_PASSWORD
          valueFrom:
            secretKeyRef:
              name: db-secret
              key: password
      
      # 挂载卷
      volumeMounts:
        - name: config
          mountPath: /etc/config
        - name: data
          mountPath: /data
      
      # 健康检查
      livenessProbe:
        httpGet:
          path: /healthz
          port: 8080
        initialDelaySeconds: 30
        periodSeconds: 10
      
      readinessProbe:
        httpGet:
          path: /ready
          port: 8080
        initialDelaySeconds: 5
        periodSeconds: 5
  
  # 卷配置
  volumes:
    - name: config
      configMap:
        name: myapp-config
    - name: data
      persistentVolumeClaim:
        claimName: myapp-data
  
  # 调度配置
  nodeSelector:
    disk: ssd
  
  # 重启策略
  restartPolicy: Always

多容器Pod模式

Sidecar模式

apiVersion: v1
kind: Pod
metadata:
  name: app-with-logging
spec:
  containers:
    - name: app
      image: myapp:v1
    - name: log-collector
      image: fluentd:latest
      volumeMounts:
        - name: logs
          mountPath: /var/log
  volumes:
    - name: logs
      emptyDir: {}

Init容器

apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  initContainers:
    - name: init-db
      image: busybox
      command: ['sh', '-c', 'until nslookup mysql-service; do sleep 2; done']
  
  containers:
    - name: myapp
      image: myapp:v1

Pod调度

亲和性

spec:
  affinity:
    nodeAffinity:
      requiredDuringSchedulingIgnoredDuringExecution:
        nodeSelectorTerms:
          - matchExpressions:
              - key: disktype
                operator: In
                values:
                  - ssd

污点和容忍

spec:
  tolerations:
    - key: "dedicated"
      operator: "Equal"
      value: "special-user"
      effect: "NoSchedule"

实践：部署应用Pod

# 快速创建Pod
kubectl run nginx --image=nginx --port=80

# 查看Pod
kubectl get pods -o wide

# 查看Pod详情
kubectl describe pod nginx

# 进入Pod
kubectl exec -it nginx -- /bin/bash

# 查看Pod日志
kubectl logs nginx

# 删除Pod
kubectl delete pod nginx

Pod调试

# 查看Pod事件
kubectl describe pod pod_name

# 查看Pod日志
kubectl logs pod_name
kubectl logs pod_name -c container_name

# 调试命令
kubectl exec -it pod_name -- sh

# 创建调试Pod
kubectl run debug --image=busybox --rm -it -- /bin/sh

总结

Pod是Kubernetes的核心概念。理解Pod的生命周期、配置和调度机制，是掌握Kubernetes的关键。