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与 K8s 部署衔接：Deployment、Service、Ingress ​

随着容器化应用的普及，Kubernetes（K8s）已成为容器编排的事实标准。Docker 容器作为 K8s 的基本部署单元，需要与 K8s 的核心概念如 Deployment、Service 和 Ingress 紧密衔接。本篇文章将深入探讨如何将 Docker 容器与 K8s 部署进行有效整合，实现生产级的容器化应用部署。

一、Kubernetes 核心概念 ​

在深入具体配置之前，我们需要理解 K8s 的几个核心概念：

1. Pod ​

Pod 是 K8s 中最小的部署单元，可以包含一个或多个容器：

yaml
# 简单的 Pod 配置
apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: myapp:latest
    ports:
    - containerPort: 3000

2. Deployment ​

Deployment 管理 Pod 的部署和更新，提供声明式的更新能力：

yaml
# Deployment 配置示例
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
  labels:
    app: myapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myapp:latest
        ports:
        - containerPort: 3000

3. Service ​

Service 为 Pod 提供稳定的网络访问入口：

yaml
# Service 配置示例
apiVersion: v1
kind: Service
metadata:
  name: myapp-service
spec:
  selector:
    app: myapp
  ports:
    - protocol: TCP
      port: 80
      targetPort: 3000
  type: ClusterIP

4. Ingress ​

Ingress 管理外部访问集群服务的 HTTP 和 HTTPS 路由：

yaml
# Ingress 配置示例
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /
spec:
  rules:
  - host: myapp.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: myapp-service
            port:
              number: 80

二、从 Docker 到 K8s 的迁移 ​

将 Docker 容器部署迁移到 K8s 需要考虑多个方面：

1. 镜像准备 ​

确保 Docker 镜像符合 K8s 的要求：

dockerfile
# 优化的 Dockerfile 用于 K8s 部署
FROM node:18-alpine

# 创建非 root 用户
RUN addgroup -g 1001 -S nodejs && \
    adduser -S nextjs -u 1001

WORKDIR /app

# 复制依赖文件
COPY package*.json ./
RUN npm ci --only=production && npm cache clean --force

# 复制应用代码
COPY . .

# 更改文件所有权
RUN chown -R nextjs:nodejs /app
USER nextjs

# 健康检查
HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
  CMD curl -f http://localhost:3000/health || exit 1

EXPOSE 3000
CMD ["node", "server.js"]

2. Deployment 配置 ​

创建适合生产环境的 Deployment 配置：

yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
  labels:
    app: myapp
    version: v1.0.0
spec:
  replicas: 3
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
        version: v1.0.0
    spec:
      containers:
      - name: myapp
        image: myapp:latest
        imagePullPolicy: Always
        ports:
        - containerPort: 3000
          name: http
        env:
        - name: NODE_ENV
          value: "production"
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: myapp-secrets
              key: database-url
        resources:
          requests:
            memory: "128Mi"
            cpu: "250m"
          limits:
            memory: "256Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /health
            port: 3000
          initialDelaySeconds: 60
          periodSeconds: 30
        readinessProbe:
          httpGet:
            path: /ready
            port: 3000
          initialDelaySeconds: 30
          periodSeconds: 10

3. Service 配置 ​

创建 Service 以暴露应用：

yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp-service
  labels:
    app: myapp
spec:
  selector:
    app: myapp
  ports:
  - name: http
    protocol: TCP
    port: 80
    targetPort: 3000
  type: ClusterIP

三、高级 K8s 配置 ​

1. ConfigMap 和 Secret ​

外部化配置和敏感信息：

yaml
# ConfigMap 示例
apiVersion: v1
kind: ConfigMap
metadata:
  name: myapp-config
data:
  NODE_ENV: "production"
  LOG_LEVEL: "info"
  API_TIMEOUT: "5000"

---
# Secret 示例
apiVersion: v1
kind: Secret
metadata:
  name: myapp-secrets
type: Opaque
data:
  database-url: <base64-encoded-database-url>
  api-key: <base64-encoded-api-key>

在 Deployment 中使用 ConfigMap 和 Secret：

yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
spec:
  template:
    spec:
      containers:
      - name: myapp
        # ... 其他配置
        envFrom:
        - configMapRef:
            name: myapp-config
        env:
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: myapp-secrets
              key: database-url

2. PersistentVolume 和 PersistentVolumeClaim ​

处理持久化存储：

yaml
# PersistentVolume 示例
apiVersion: v1
kind: PersistentVolume
metadata:
  name: myapp-pv
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  storageClassName: manual
  hostPath:
    path: /data/myapp

---
# PersistentVolumeClaim 示例
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: myapp-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
  storageClassName: manual

在 Deployment 中使用 PVC：

yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
spec:
  template:
    spec:
      containers:
      - name: myapp
        # ... 其他配置
        volumeMounts:
        - name: data
          mountPath: /app/data
      volumes:
      - name: data
        persistentVolumeClaim:
          claimName: myapp-pvc

四、Ingress 配置和路由 ​

1. 基本 Ingress 配置 ​

yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp-ingress
  annotations:
    kubernetes.io/ingress.class: nginx
    nginx.ingress.kubernetes.io/ssl-redirect: "true"
spec:
  tls:
  - hosts:
    - myapp.example.com
    secretName: myapp-tls
  rules:
  - host: myapp.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: myapp-service
            port:
              number: 80

2. 多路径路由 ​

yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp-ingress
  annotations:
    nginx.ingress.kubernetes.io/rewrite-target: /$2
spec:
  rules:
  - host: myapp.example.com
    http:
      paths:
      - path: /api(/|$)(.*)
        pathType: Prefix
        backend:
          service:
            name: myapp-api-service
            port:
              number: 80
      - path: /admin(/|$)(.*)
        pathType: Prefix
        backend:
          service:
            name: myapp-admin-service
            port:
              number: 80
      - path: /(.*)
        pathType: Prefix
        backend:
          service:
            name: myapp-frontend-service
            port:
              number: 80

五、监控和日志 ​

1. 健康检查配置 ​

yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
spec:
  template:
    spec:
      containers:
      - name: myapp
        # ... 其他配置
        livenessProbe:
          httpGet:
            path: /healthz
            port: 3000
          initialDelaySeconds: 60
          periodSeconds: 30
          timeoutSeconds: 10
          failureThreshold: 3
        readinessProbe:
          httpGet:
            path: /ready
            port: 3000
          initialDelaySeconds: 30
          periodSeconds: 10
          timeoutSeconds: 5
          failureThreshold: 3

2. 资源限制和请求 ​

yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
spec:
  template:
    spec:
      containers:
      - name: myapp
        # ... 其他配置
        resources:
          requests:
            memory: "128Mi"
            cpu: "250m"
          limits:
            memory: "256Mi"
            cpu: "500m"

六、完整的部署示例 ​

以下是一个完整的 K8s 部署示例：

yaml
# namespace.yaml
apiVersion: v1
kind: Namespace
metadata:
  name: myapp

---
# configmap.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: myapp-config
  namespace: myapp
data:
  NODE_ENV: "production"
  LOG_LEVEL: "info"

---
# secret.yaml
apiVersion: v1
kind: Secret
metadata:
  name: myapp-secrets
  namespace: myapp
type: Opaque
data:
  database-url: <base64-encoded-value>

---
# deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
  namespace: myapp
  labels:
    app: myapp
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp
        image: myapp:latest
        ports:
        - containerPort: 3000
        envFrom:
        - configMapRef:
            name: myapp-config
        env:
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: myapp-secrets
              key: database-url
        resources:
          requests:
            memory: "128Mi"
            cpu: "250m"
          limits:
            memory: "256Mi"
            cpu: "500m"
        livenessProbe:
          httpGet:
            path: /health
            port: 3000
          initialDelaySeconds: 60
          periodSeconds: 30
        readinessProbe:
          httpGet:
            path: /ready
            port: 3000
          initialDelaySeconds: 30
          periodSeconds: 10

---
# service.yaml
apiVersion: v1
kind: Service
metadata:
  name: myapp-service
  namespace: myapp
spec:
  selector:
    app: myapp
  ports:
  - port: 80
    targetPort: 3000
  type: ClusterIP

---
# ingress.yaml
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp-ingress
  namespace: myapp
  annotations:
    kubernetes.io/ingress.class: nginx
spec:
  rules:
  - host: myapp.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: myapp-service
            port:
              number: 80

一句话总结 ​

将 Docker 容器与 Kubernetes 部署衔接需要理解 K8s 的核心概念如 Deployment、Service 和 Ingress，并通过合理的资源配置、健康检查、存储管理和网络策略来实现生产级的容器化应用部署。

通过这种方式，我们可以充分利用 Docker 的容器化优势和 K8s 的编排能力，构建高可用、可扩展的现代化应用架构。在实际部署中，还需要考虑监控、日志、安全和备份等运维方面的要求。

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