## 21.7 实战案例：Go/Rust/数据库/微服务

本节通过实际项目案例演示如何为不同类型的应用构建最优化的 Docker 镜像，以及如何使用 Docker Compose 构建完整的开发和生产环境。

### 21.7.1 Go 应用的最小化镜像构建

Go 语言因其编译为静态二进制和快速启动而特别适合容器化。以下展示如何构建极小的 Go 应用镜像。

#### 超小 Go Web 服务

**应用代码（main.go）：**

```go
package main

import (
	"fmt"
	"log"
	"net/http"
	"os"
)

func healthHandler(w http.ResponseWriter, r *http.Request) {
	w.Header().Set("Content-Type", "application/json")
	fmt.Fprintf(w, `{"status":"healthy","version":"1.0.0"}`)
}

func helloHandler(w http.ResponseWriter, r *http.Request) {
	hostname, _ := os.Hostname()
	w.Header().Set("Content-Type", "application/json")
	fmt.Fprintf(w, `{"message":"Hello from %s","version":"1.0.0"}`, hostname)
}

func main() {
	http.HandleFunc("/health", healthHandler)
	http.HandleFunc("/hello", helloHandler)
	http.HandleFunc("/", helloHandler)

	port := ":8080"
	log.Printf("Server starting on %s", port)

	if err := http.ListenAndServe(port, nil); err != nil {
		log.Fatalf("Server failed: %v", err)
	}
}
```

**多阶段 Dockerfile：**

```dockerfile
# Stage 1: 构建阶段
FROM golang:1.20-alpine AS builder

WORKDIR /build

# 安装构建依赖
RUN apk add --no-cache git ca-certificates tzdata

# 复制模块文件（利用缓存）
COPY go.mod go.sum ./
RUN go mod download

# 复制源代码
COPY . .

# 构建静态二进制
# -ldflags="-w -s" 去除调试符号减小体积
RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 go build \
    -a -installsuffix cgo \
    -ldflags="-w -s -X main.Version=1.0.0 -X main.BuildTime=$(date -u +'%Y-%m-%dT%H:%M:%SZ')" \
    -o app .

# Stage 2: 运行阶段（scratch 镜像）
FROM scratch

# 复制 CA 证书（用于 HTTPS）
COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/

# 复制时区数据（用于时间处理）
COPY --from=builder /usr/share/zoneinfo /usr/share/zoneinfo

# 复制应用二进制
COPY --from=builder /build/app /app

EXPOSE 8080

# 使用绝对路径作为 ENTRYPOINT
ENTRYPOINT ["/app"]
```

**构建和测试：**

```bash
# 构建镜像
docker build -t go-app:latest .

# 检查镜像大小
docker images go-app

# 运行容器
docker run -d -p 8080:8080 --name go-demo go-app:latest

# 测试应用
curl http://localhost:8080/health | jq .

# 进入容器验证
docker exec go-demo ls -la /
# 只包含 /app 和系统必要文件

# 镜像大小通常 < 10MB（相比 golang:1.20-alpine 的 ~1GB）
docker history go-app:latest
```

**go.mod 和 go.sum 示例：**

```
module github.com/example/go-app

go 1.20

require (
    // 如果需要依赖
)
```

#### 带依赖的 Go 应用

**应用代码（使用 Gin 框架）：**

```go
package main

import (
	"github.com/gin-gonic/gin"
	"log"
)

func main() {
	router := gin.Default()

	router.GET("/health", func(c *gin.Context) {
		c.JSON(200, gin.H{
			"status": "ok",
		})
	})

	router.GET("/api/users", func(c *gin.Context) {
		c.JSON(200, gin.H{
			"users": []string{"alice", "bob"},
		})
	})

	log.Fatal(router.Run(":8080"))
}
```

**优化的 Dockerfile：**

```dockerfile
FROM golang:1.20-alpine AS builder

WORKDIR /src

RUN apk add --no-cache git ca-certificates tzdata

COPY go.mod go.sum ./
RUN go mod download

COPY . .

RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
    go build -a -installsuffix cgo \
    -ldflags="-w -s" \
    -o app .

# 最终镜像
FROM alpine:3.17

RUN apk add --no-cache ca-certificates tzdata

WORKDIR /root/

COPY --from=builder /src/app .

EXPOSE 8080

CMD ["./app"]
```

### 21.7.2 Rust 应用的最小化镜像构建

Rust 因其性能和安全性在系统级应用中备受青睐。

**应用代码（main.rs）：**

```rust
use actix_web::{web, App, HttpServer, HttpResponse};
use std::sync::Mutex;

#[actix_web::main]
async fn main() -> std::io::Result<()> {
    println!("Starting server on 0.0.0.0:8080");

    HttpServer::new(|| {
        App::new()
            .route("/health", web::get().to(health))
            .route("/hello", web::get().to(hello))
    })
    .bind("0.0.0.0:8080")?
    .run()
    .await
}

async fn health() -> HttpResponse {
    HttpResponse::Ok().json(serde_json::json!({
        "status": "healthy"
    }))
}

async fn hello() -> HttpResponse {
    HttpResponse::Ok().json(serde_json::json!({
        "message": "Hello from Rust"
    }))
}
```

**Cargo.toml：**

```toml
[package]
name = "rust-app"
version = "0.1.0"
edition = "2021"

[[bin]]
name = "rust-app"
path = "src/main.rs"

[dependencies]
actix-web = "4.4"
tokio = { version = "1.35", features = ["full"] }
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"
```

**多阶段构建 Dockerfile：**

```dockerfile
# Stage 1: 编译
FROM rust:1.75-alpine AS builder

RUN apk add --no-cache musl-dev

WORKDIR /src

COPY Cargo.* ./
COPY src ./src

# 构建优化的发布版本
RUN cargo build --release

# Stage 2: 运行镜像
FROM alpine:3.17

RUN apk add --no-cache ca-certificates

COPY --from=builder /src/target/release/rust-app /app

EXPOSE 8080

CMD ["/app"]
```

**构建和验证：**

```bash
docker build -t rust-app:latest .
docker run -d -p 8080:8080 rust-app:latest
curl http://localhost:8080/health | jq .

# Rust 应用通常比 Go 更小：5-20MB（取决于依赖）
docker images rust-app
```

### 21.7.3 数据库容器化最佳实践

#### PostgreSQL 生产部署

**自定义 PostgreSQL 镜像：**

```dockerfile
FROM postgres:16-alpine

# 安装额外工具
RUN apk add --no-cache \
    postgresql-contrib \
    pg-stat-monitor \
    curl

# 复制初始化脚本
COPY init-db.sql /docker-entrypoint-initdb.d/
COPY health-check.sh /

RUN chmod +x /health-check.sh

HEALTHCHECK --interval=10s --timeout=5s --start-period=40s --retries=3 \
    CMD /health-check.sh

EXPOSE 5432
```

**初始化脚本（init-db.sql）：**

```sql
-- 创建自定义用户
CREATE USER appuser WITH PASSWORD 'secure_password';

-- 创建数据库
CREATE DATABASE myappdb OWNER appuser;

-- 创建扩展
\c myappdb

CREATE EXTENSION IF NOT EXISTS uuid-ossp;
CREATE EXTENSION IF NOT EXISTS hstore;
CREATE EXTENSION IF NOT EXISTS pg_trgm;

-- 创建表
CREATE TABLE users (
    id UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
    username VARCHAR(255) NOT NULL UNIQUE,
    email VARCHAR(255) NOT NULL UNIQUE,
    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

-- 创建索引
CREATE INDEX idx_users_username ON users (username);
CREATE INDEX idx_users_email ON users (email);

-- 授予权限
GRANT CONNECT ON DATABASE myappdb TO appuser;
GRANT USAGE ON SCHEMA public TO appuser;
GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO appuser;
GRANT ALL PRIVILEGES ON ALL SEQUENCES IN SCHEMA public TO appuser;
```

**健康检查脚本（health-check.sh）：**

```bash
#!/bin/bash

PGPASSWORD=$POSTGRES_PASSWORD pg_isready \
  -h localhost \
  -U $POSTGRES_USER \
  -d $POSTGRES_DB \
  -p 5432 > /dev/null 2>&1

exit $?
```

**Docker Compose 配置：**

```yaml
version: '3.9'

services:
  postgres:
    build:
      context: .
      dockerfile: Dockerfile.postgres
    container_name: postgres-db
    environment:
      POSTGRES_DB: myappdb
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: postgres_password
      POSTGRES_INITDB_ARGS: "--encoding=UTF8 --locale=en_US.UTF-8"
    volumes:
      - postgres_data:/var/lib/postgresql/data
      - ./backups:/backups
    ports:
      - "5432:5432"
    networks:
      - backend
    restart: unless-stopped
    logging:
      driver: "json-file"
      options:
        max-size: "10m"
        max-file: "3"

  # 备份服务
  backup:
    image: postgres:16-alpine
    depends_on:
      - postgres
    environment:
      PGPASSWORD: postgres_password
    volumes:
      - ./backups:/backups
    command: |
      sh -c 'while true; do
        pg_dump -h postgres -U postgres -d myappdb > /backups/backup_$$(date +%Y%m%d_%H%M%S).sql
        echo "Backup completed at $$(date)"
        sleep 86400
      done'
    networks:
      - backend

volumes:
  postgres_data:
    driver: local

networks:
  backend:
    driver: bridge
```

**性能优化配置：**

```yaml
version: '3.9'

services:
  postgres:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: myappdb
    command:
      - "postgres"
      - "-c"
      - "max_connections=200"
      - "-c"
      - "shared_buffers=256MB"
      - "-c"
      - "effective_cache_size=1GB"
      - "-c"
      - "maintenance_work_mem=64MB"
      - "-c"
      - "checkpoint_completion_target=0.9"
      - "-c"
      - "wal_buffers=16MB"
      - "-c"
      - "default_statistics_target=100"
      - "-c"
      - "random_page_cost=1.1"
      - "-c"
      - "effective_io_concurrency=200"
      - "-c"
      - "work_mem=1310kB"
      - "-c"
      - "min_wal_size=1GB"
      - "-c"
      - "max_wal_size=4GB"
      - "-c"
      - "max_worker_processes=4"
      - "-c"
      - "max_parallel_workers_per_gather=2"
      - "-c"
      - "max_parallel_workers=4"
      - "-c"
      - "max_parallel_maintenance_workers=2"
    volumes:
      - postgres_data:/var/lib/postgresql/data
    ports:
      - "5432:5432"

volumes:
  postgres_data:
```

#### MySQL/MariaDB 部署

```dockerfile
FROM mariadb:11

# 复制自定义配置
COPY my.cnf /etc/mysql/conf.d/custom.cnf

# 初始化脚本
COPY init.sql /docker-entrypoint-initdb.d/

EXPOSE 3306

HEALTHCHECK --interval=30s --timeout=10s --retries=3 \
    CMD mariadb-admin ping -h localhost || exit 1
```

**自定义 my.cnf：**

```ini
[mysqld]
# 性能优化
max_connections = 200
default_storage_engine = InnoDB
innodb_buffer_pool_size = 1GB
innodb_log_file_size = 256MB
query_cache_type = 0
query_cache_size = 0

# 日志配置
log_error = /var/log/mysql/error.log
slow_query_log = 1
slow_query_log_file = /var/log/mysql/slow.log
long_query_time = 2

# 复制配置
server_id = 1
log_bin = mysql-bin
binlog_format = ROW
```

#### Redis 缓存部署

```dockerfile
FROM redis:7-alpine

# 复制 Redis 配置
COPY redis.conf /usr/local/etc/redis/redis.conf

# 使用配置文件启动
CMD ["redis-server", "/usr/local/etc/redis/redis.conf"]

EXPOSE 6379

HEALTHCHECK --interval=5s --timeout=3s --retries=5 \
    CMD redis-cli ping || exit 1
```

**redis.conf 配置：**

```conf
# 绑定地址
bind 0.0.0.0

# 端口
port 6379

# 密码保护
requirepass your_secure_password

# 内存管理
maxmemory 512mb
maxmemory-policy allkeys-lru

# 持久化
save 900 1
save 300 10
save 60 10000

# AOF 持久化
appendonly yes
appendfsync everysec

# 日志
loglevel notice
logfile ""

# 客户端输出缓冲限制
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit slave 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60
```

### 21.7.4 微服务架构的 Docker Compose 编排

**三层微服务架构示例：**

```yaml
version: '3.9'

services:
  # 前端服务
  frontend:
    build:
      context: ./frontend
      dockerfile: Dockerfile
    container_name: frontend
    ports:
      - "3000:3000"
    environment:
      REACT_APP_API_URL: http://localhost:8000
      NODE_ENV: production
    depends_on:
      - api
    networks:
      - frontend-network
    restart: unless-stopped
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:3000"]
      interval: 30s
      timeout: 10s
      retries: 3

  # API 服务
  api:
    build:
      context: ./api
      dockerfile: Dockerfile
    container_name: api
    ports:
      - "8000:8000"
    environment:
      DATABASE_URL: postgresql://appuser:password@postgres:5432/myappdb
      REDIS_URL: redis://redis:6379
      LOG_LEVEL: info
    depends_on:
      postgres:
        condition: service_healthy
      redis:
        condition: service_healthy
    networks:
      - frontend-network
      - backend-network
    restart: unless-stopped
    healthcheck:
      test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
      interval: 30s
      timeout: 10s
      retries: 3
    deploy:
      resources:
        limits:
          cpus: '1'
          memory: 512M
        reservations:
          cpus: '0.5'
          memory: 256M

  # PostgreSQL 数据库
  postgres:
    image: postgres:16-alpine
    container_name: postgres
    environment:
      POSTGRES_DB: myappdb
      POSTGRES_USER: appuser
      POSTGRES_PASSWORD: password
    volumes:
      - postgres_data:/var/lib/postgresql/data
      - ./db/init.sql:/docker-entrypoint-initdb.d/init.sql
    networks:
      - backend-network
    restart: unless-stopped
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U appuser -d myappdb"]
      interval: 10s
      timeout: 5s
      retries: 5

  # Redis 缓存
  redis:
    image: redis:7-alpine
    container_name: redis
    command: redis-server --appendonly yes --requirepass redispass
    volumes:
      - redis_data:/data
    networks:
      - backend-network
    restart: unless-stopped
    healthcheck:
      test: ["CMD", "redis-cli", "--raw", "incr", "ping"]
      interval: 10s
      timeout: 5s
      retries: 5

  # Nginx 反向代理
  nginx:
    image: nginx:alpine
    container_name: nginx
    ports:
      - "80:80"
      - "443:443"
    volumes:
      - ./nginx/nginx.conf:/etc/nginx/nginx.conf:ro
      - ./nginx/conf.d:/etc/nginx/conf.d:ro
      - ./ssl:/etc/nginx/ssl:ro
    depends_on:
      - frontend
      - api
    networks:
      - frontend-network
    restart: unless-stopped
    healthcheck:
      test: ["CMD", "wget", "--quiet", "--tries=1", "--spider", "http://localhost/health"]
      interval: 30s
      timeout: 10s
      retries: 3

volumes:
  postgres_data:
    driver: local
  redis_data:
    driver: local

networks:
  frontend-network:
    driver: bridge
  backend-network:
    driver: bridge
```

**nginx.conf 配置：**

```nginx
upstream frontend {
    server frontend:3000;
}

upstream api {
    server api:8000;
}

server {
    listen 80;
    server_name localhost;
    client_max_body_size 100M;

    # 健康检查端点
    location /health {
        access_log off;
        return 200 "OK\n";
        add_header Content-Type text/plain;
    }

    # 前端应用
    location / {
        proxy_pass http://frontend;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
    }

    # API 接口
    location /api/ {
        proxy_pass http://api/;
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_redirect off;

        # WebSocket 支持
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }

    # 静态资源缓存
    location ~* ^.+\.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
        proxy_pass http://frontend;
        expires 30d;
        add_header Cache-Control "public, immutable";
    }
}
```

### 21.7.5 使用 VS Code Dev Containers

Dev Containers 让整个开发环境容器化，提升团队一致性。

**.devcontainer/devcontainer.json：**

```json
{
  "name": "Python Dev Environment",
  "image": "mcr.microsoft.com/devcontainers/python:3.11",

  "features": {
    "ghcr.io/devcontainers/features/docker-in-docker:2": {},
    "ghcr.io/devcontainers/features/git:1": {}
  },

  "customizations": {
    "vscode": {
      "extensions": [
        "ms-python.python",
        "ms-python.vscode-pylance",
        "ms-python.pylint",
        "charliermarsh.ruff",
        "ms-vscode-remote.remote-containers"
      ],
      "settings": {
        "python.linting.enabled": true,
        "python.linting.pylintEnabled": true,
        "python.formatting.provider": "black",
        "[python]": {
          "editor.formatOnSave": true,
          "editor.defaultFormatter": "ms-python.python"
        }
      }
    }
  },

  "postCreateCommand": "pip install -r requirements.txt && pip install pytest black pylint",

  "forwardPorts": [8000, 5432, 6379],
  "portsAttributes": {
    "8000": {
      "label": "Application",
      "onAutoForward": "notify"
    },
    "5432": {
      "label": "PostgreSQL",
      "onAutoForward": "ignore"
    },
    "6379": {
      "label": "Redis",
      "onAutoForward": "ignore"
    }
  },

  "mounts": [
    "source=${localEnv:HOME}/.ssh,target=/home/vscode/.ssh,readonly"
  ],

  "remoteUser": "vscode"
}
```

**.devcontainer/Dockerfile：**

```dockerfile
FROM mcr.microsoft.com/devcontainers/python:3.11

# 安装额外工具
RUN apt-get update && apt-get install -y \
    postgresql-client \
    redis-tools \
    curl \
    git \
    && rm -rf /var/lib/apt/lists/*

# 创建虚拟环境
RUN python -m venv /opt/venv
ENV PATH="/opt/venv/bin:$PATH"

WORKDIR /workspace
```

**docker-compose 用于 Dev Containers：**

```yaml
# .devcontainer/docker-compose.yml
version: '3.9'

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
    environment:
      DATABASE_URL: postgresql://dev:dev@postgres:5432/myapp
      REDIS_URL: redis://redis:6379
    volumes:
      - ..:/workspace:cached
    ports:
      - "8000:8000"
    depends_on:
      - postgres
      - redis

  postgres:
    image: postgres:16-alpine
    environment:
      POSTGRES_USER: dev
      POSTGRES_PASSWORD: dev
      POSTGRES_DB: myapp
    volumes:
      - postgres_data:/var/lib/postgresql/data

  redis:
    image: redis:7-alpine

volumes:
  postgres_data:
```