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系统设计 ​

📖 概述 ​

系统设计是构建大规模、高性能、可靠系统的方法论。它涵盖了从需求分析到架构设计，从技术选型到容量规划的完整过程，是软件工程师必须掌握的核心技能。

🎯 学习目标 ​

  • 掌握系统设计的基本原则和方法论
  • 理解大规模系统的架构模式和技术选型
  • 学习容量规划和性能优化技术
  • 实现可扩展、高可用的系统架构

🏗️ 系统设计框架 ​

1. 设计方法论 ​

javascript
// 系统设计框架
class SystemDesignFramework {
  constructor() {
    this.requirementAnalyzer = new RequirementAnalyzer()
    this.architectureDesigner = new ArchitectureDesigner()
    this.technologySelector = new TechnologySelector()
    this.capacityPlanner = new CapacityPlanner()
    this.performanceOptimizer = new PerformanceOptimizer()
    this.reliabilityEngineer = new ReliabilityEngineer()
  }
  
  // 需求分析器
  class RequirementAnalyzer {
    constructor() {
      this.functionalRequirements = []
      this.nonFunctionalRequirements = {}
      this.constraints = []
      this.assumptions = []
    }
    
    // 分析功能需求
    analyzeFunctionalRequirements(userStories) {
      const requirements = []
      
      userStories.forEach(story => {
        const requirement = {
          id: this.generateRequirementId(),
          title: story.title,
          description: story.description,
          acceptanceCriteria: story.acceptanceCriteria,
          priority: story.priority || 'medium',
          complexity: this.estimateComplexity(story),
          dependencies: story.dependencies || [],
          estimatedEffort: this.estimateEffort(story)
        }
        
        requirements.push(requirement)
      })
      
      this.functionalRequirements = requirements
      return requirements
    }
    
    // 分析非功能需求
    analyzeNonFunctionalRequirements(nfrSpec) {
      this.nonFunctionalRequirements = {
        performance: {
          responseTime: nfrSpec.performance?.responseTime || '< 200ms',
          throughput: nfrSpec.performance?.throughput || '1000 req/s',
          concurrency: nfrSpec.performance?.concurrency || 1000
        },
        scalability: {
          userLoad: nfrSpec.scalability?.userLoad || '100k users',
          dataVolume: nfrSpec.scalability?.dataVolume || '1TB',
          growthRate: nfrSpec.scalability?.growthRate || '50% yearly'
        },
        availability: {
          uptime: nfrSpec.availability?.uptime || '99.9%',
          mtbf: nfrSpec.availability?.mtbf || '720 hours',
          mttr: nfrSpec.availability?.mttr || '4 hours'
        },
        reliability: {
          errorRate: nfrSpec.reliability?.errorRate || '< 0.1%',
          dataConsistency: nfrSpec.reliability?.dataConsistency || 'eventual',
          faultTolerance: nfrSpec.reliability?.faultTolerance || 'graceful degradation'
        },
        security: {
          authentication: nfrSpec.security?.authentication || 'multi-factor',
          authorization: nfrSpec.security?.authorization || 'role-based',
          dataProtection: nfrSpec.security?.dataProtection || 'encryption at rest/transit',
          compliance: nfrSpec.security?.compliance || []
        },
        usability: {
          userExperience: nfrSpec.usability?.userExperience || 'intuitive',
          accessibility: nfrSpec.usability?.accessibility || 'WCAG 2.1',
          supportedDevices: nfrSpec.usability?.supportedDevices || ['web', 'mobile']
        }
      }
      
      return this.nonFunctionalRequirements
    }
    
    // 识别约束条件
    identifyConstraints(projectContext) {
      this.constraints = [
        {
          type: 'budget',
          description: `预算限制: ${projectContext.budget || '待定'}`,
          impact: 'high'
        },
        {
          type: 'timeline',
          description: `时间约束: ${projectContext.timeline || '6个月'}`,
          impact: 'high'
        },
        {
          type: 'technology',
          description: `技术栈限制: ${projectContext.techStack?.join(', ') || '无限制'}`,
          impact: 'medium'
        },
        {
          type: 'team',
          description: `团队规模: ${projectContext.teamSize || '5-10人'}`,
          impact: 'medium'
        },
        {
          type: 'compliance',
          description: `合规要求: ${projectContext.compliance?.join(', ') || '无'}`,
          impact: 'high'
        }
      ]
      
      return this.constraints
    }
    
    estimateComplexity(story) {
      // 简化的复杂度评估
      const factors = {
        dataComplexity: story.dataEntities?.length || 1,
        integrationPoints: story.integrations?.length || 0,
        businessLogicComplexity: story.rules?.length || 1,
        userInterfaceComplexity: story.screens?.length || 1
      }
      
      const totalScore = Object.values(factors).reduce((sum, score) => sum + score, 0)
      
      if (totalScore <= 5) return 'low'
      if (totalScore <= 10) return 'medium'
      return 'high'
    }
    
    estimateEffort(story) {
      const complexityMultiplier = {
        low: 1,
        medium: 2,
        high: 4
      }
      
      const baseEffort = 8 // 8小时基础工作量
      const complexity = this.estimateComplexity(story)
      
      return baseEffort * complexityMultiplier[complexity]
    }
    
    generateRequirementId() {
      return `REQ_${Date.now()}_${Math.random().toString(36).substr(2, 4).toUpperCase()}`
    }
    
    // 生成需求文档
    generateRequirementDocument() {
      return {
        functional: this.functionalRequirements,
        nonFunctional: this.nonFunctionalRequirements,
        constraints: this.constraints,
        assumptions: this.assumptions,
        summary: {
          totalRequirements: this.functionalRequirements.length,
          complexityDistribution: this.getComplexityDistribution(),
          estimatedEffort: this.getTotalEstimatedEffort()
        }
      }
    }
    
    getComplexityDistribution() {
      const distribution = { low: 0, medium: 0, high: 0 }
      
      this.functionalRequirements.forEach(req => {
        distribution[req.complexity]++
      })
      
      return distribution
    }
    
    getTotalEstimatedEffort() {
      return this.functionalRequirements.reduce((total, req) => total + req.estimatedEffort, 0)
    }
  }
  
  // 架构设计器
  class ArchitectureDesigner {
    constructor() {
      this.architecturePatterns = new Map()
      this.componentRegistry = new Map()
      this.initializePatterns()
    }
    
    initializePatterns() {
      // 注册常见架构模式
      this.architecturePatterns.set('monolith', {
        name: '单体架构',
        description: '所有功能部署在单一应用中',
        pros: ['简单部署', '开发效率高', '易于测试'],
        cons: ['难以扩展', '技术栈锁定', '单点故障'],
        suitableFor: ['小型应用', 'MVP', '团队规模小']
      })
      
      this.architecturePatterns.set('microservices', {
        name: '微服务架构',
        description: '应用拆分为多个独立的服务',
        pros: ['独立部署', '技术多样性', '故障隔离'],
        cons: ['复杂度高', '网络延迟', '数据一致性'],
        suitableFor: ['大型应用', '高并发', '大团队']
      })
      
      this.architecturePatterns.set('serverless', {
        name: '无服务器架构',
        description: '基于函数即服务的架构',
        pros: ['按需付费', '自动扩展', '运维简化'],
        cons: ['冷启动', '厂商锁定', '调试困难'],
        suitableFor: ['事件驱动', '轻量计算', '初创企业']
      })
      
      this.architecturePatterns.set('layered', {
        name: '分层架构',
        description: '按职责分层的架构模式',
        pros: ['职责清晰', '易于理解', '可维护性好'],
        cons: ['性能开销', '层间耦合', '变更影响大'],
        suitableFor: ['企业应用', '复杂业务逻辑', '传统系统']
      })
    }
    
    // 选择架构模式
    selectArchitecturePattern(requirements, constraints) {
      const analysis = {
        recommendedPatterns: [],
        reasoning: []
      }
      
      // 基于需求分析推荐架构模式
      const userLoad = this.parseUserLoad(requirements.nonFunctional?.scalability?.userLoad)
      const teamSize = this.parseTeamSize(constraints)
      const complexity = this.assessSystemComplexity(requirements)
      
      if (userLoad < 10000 && teamSize <= 5 && complexity === 'low') {
        analysis.recommendedPatterns.push({
          pattern: 'monolith',
          score: 90,
          reason: '小规模应用，团队较小，适合单体架构'
        })
      }
      
      if (userLoad > 50000 || teamSize > 10 || complexity === 'high') {
        analysis.recommendedPatterns.push({
          pattern: 'microservices',
          score: 85,
          reason: '大规模应用，需要微服务架构支持'
        })
      }
      
      if (requirements.functional.some(req => req.title.includes('事件') || req.title.includes('触发'))) {
        analysis.recommendedPatterns.push({
          pattern: 'serverless',
          score: 75,
          reason: '事件驱动场景，适合无服务器架构'
        })
      }
      
      // 排序推荐
      analysis.recommendedPatterns.sort((a, b) => b.score - a.score)
      
      return analysis
    }
    
    // 设计系统架构
    designSystemArchitecture(pattern, requirements) {
      const architecture = {
        pattern: pattern,
        components: [],
        dataFlow: [],
        integrationPoints: [],
        deploymentModel: {},
        scalingStrategy: {}
      }
      
      switch (pattern) {
        case 'microservices':
          architecture.components = this.designMicroservicesComponents(requirements)
          architecture.dataFlow = this.designMicroservicesDataFlow(architecture.components)
          architecture.integrationPoints = this.designMicroservicesIntegrations(architecture.components)
          break
          
        case 'monolith':
          architecture.components = this.designMonolithComponents(requirements)
          architecture.dataFlow = this.designMonolithDataFlow(architecture.components)
          break
          
        case 'serverless':
          architecture.components = this.designServerlessComponents(requirements)
          architecture.dataFlow = this.designServerlessDataFlow(architecture.components)
          break
      }
      
      return architecture
    }
    
    designMicroservicesComponents(requirements) {
      const components = []
      
      // API网关
      components.push({
        name: 'API Gateway',
        type: 'gateway',
        responsibilities: ['路由', '认证', '限流', '监控'],
        technology: 'Kong/Nginx',
        scalability: 'horizontal'
      })
      
      // 根据功能需求设计微服务
      const serviceGroups = this.groupRequirementsByDomain(requirements.functional)
      
      serviceGroups.forEach(group => {
        components.push({
          name: `${group.domain} Service`,
          type: 'microservice',
          responsibilities: group.responsibilities,
          technology: 'Node.js/Express',
          database: this.selectDatabase(group.dataRequirements),
          scalability: 'horizontal'
        })
      })
      
      // 共享组件
      components.push(
        {
          name: 'Authentication Service',
          type: 'microservice',
          responsibilities: ['用户认证', '授权', 'JWT管理'],
          technology: 'Node.js/Passport',
          scalability: 'horizontal'
        },
        {
          name: 'Notification Service',
          type: 'microservice',
          responsibilities: ['邮件通知', '短信通知', '推送通知'],
          technology: 'Node.js/Nodemailer',
          scalability: 'horizontal'
        },
        {
          name: 'File Storage Service',
          type: 'microservice',
          responsibilities: ['文件上传', '文件存储', '文件访问'],
          technology: 'Node.js/AWS S3',
          scalability: 'horizontal'
        }
      )
      
      return components
    }
    
    groupRequirementsByDomain(requirements) {
      // 简化的领域划分逻辑
      const domains = new Map()
      
      requirements.forEach(req => {
        const domain = this.extractDomain(req.title)
        
        if (!domains.has(domain)) {
          domains.set(domain, {
            domain,
            responsibilities: [],
            dataRequirements: []
          })
        }
        
        domains.get(domain).responsibilities.push(req.description)
      })
      
      return Array.from(domains.values())
    }
    
    extractDomain(title) {
      // 简化的领域提取
      if (title.includes('用户') || title.includes('账户')) return 'User'
      if (title.includes('订单') || title.includes('购买')) return 'Order'
      if (title.includes('产品') || title.includes('商品')) return 'Product'
      if (title.includes('支付') || title.includes('付款')) return 'Payment'
      return 'Core'
    }
    
    selectDatabase(dataRequirements) {
      // 简化的数据库选择逻辑
      return 'PostgreSQL' // 默认选择
    }
    
    parseUserLoad(userLoadStr) {
      if (!userLoadStr) return 1000
      
      const match = userLoadStr.match(/(\d+)([k|m]?)/i)
      if (!match) return 1000
      
      const [, number, unit] = match
      const base = parseInt(number)
      
      switch (unit?.toLowerCase()) {
        case 'k': return base * 1000
        case 'm': return base * 1000000
        default: return base
      }
    }
    
    parseTeamSize(constraints) {
      const teamConstraint = constraints.find(c => c.type === 'team')
      if (!teamConstraint) return 5
      
      const match = teamConstraint.description.match(/(\d+)/)
      return match ? parseInt(match[1]) : 5
    }
    
    assessSystemComplexity(requirements) {
      const complexCount = requirements.functional.filter(req => req.complexity === 'high').length
      const totalCount = requirements.functional.length
      
      if (complexCount / totalCount > 0.5) return 'high'
      if (complexCount / totalCount > 0.2) return 'medium'
      return 'low'
    }
    
    designMicroservicesDataFlow(components) {
      const dataFlows = []
      
      // 设计典型的数据流
      dataFlows.push({
        source: 'Client',
        target: 'API Gateway',
        type: 'HTTP Request',
        data: 'User Request'
      })
      
      dataFlows.push({
        source: 'API Gateway',
        target: 'Authentication Service',
        type: 'HTTP Request',
        data: 'Token Validation'
      })
      
      // 添加更多数据流...
      
      return dataFlows
    }
    
    designMicroservicesIntegrations(components) {
      const integrations = []
      
      // 服务间通信
      integrations.push({
        type: 'synchronous',
        protocol: 'REST API',
        pattern: 'Request-Response',
        services: components.filter(c => c.type === 'microservice').map(c => c.name)
      })
      
      // 异步消息传递
      integrations.push({
        type: 'asynchronous',
        protocol: 'Message Queue',
        pattern: 'Publish-Subscribe',
        technology: 'RabbitMQ/Kafka'
      })
      
      return integrations
    }
    
    designMonolithComponents(requirements) {
      return [{
        name: 'Monolithic Application',
        type: 'monolith',
        layers: [
          'Presentation Layer',
          'Business Logic Layer',
          'Data Access Layer'
        ],
        technology: 'Node.js/Express',
        database: 'PostgreSQL'
      }]
    }
    
    designMonolithDataFlow(components) {
      return [{
        source: 'Client',
        target: 'Monolithic Application',
        type: 'HTTP Request',
        layers: ['Presentation', 'Business', 'Data']
      }]
    }
    
    designServerlessComponents(requirements) {
      const functions = []
      
      requirements.functional.forEach(req => {
        functions.push({
          name: `${req.title} Function`,
          type: 'lambda',
          trigger: this.determineTrigger(req),
          technology: 'AWS Lambda/Node.js',
          timeout: '30s',
          memory: '512MB'
        })
      })
      
      return functions
    }
    
    determineTrigger(requirement) {
      if (requirement.title.includes('API')) return 'API Gateway'
      if (requirement.title.includes('定时') || requirement.title.includes('调度')) return 'CloudWatch Events'
      if (requirement.title.includes('文件') || requirement.title.includes('上传')) return 'S3 Event'
      return 'API Gateway'
    }
    
    designServerlessDataFlow(components) {
      return components.map(comp => ({
        source: comp.trigger,
        target: comp.name,
        type: 'Event',
        processing: 'Serverless Function'
      }))
    }
  }
  
  // 技术选型器
  class TechnologySelector {
    constructor() {
      this.technologyMatrix = new Map()
      this.initializeTechnologyMatrix()
    }
    
    initializeTechnologyMatrix() {
      // 编程语言
      this.technologyMatrix.set('programming_languages', [
        {
          name: 'Node.js',
          pros: ['JavaScript生态', '高并发', '快速开发'],
          cons: ['单线程限制', 'CPU密集型弱'],
          suitableFor: ['API服务', 'Web应用', '微服务'],
          maturity: 'high',
          community: 'excellent',
          performance: 'good'
        },
        {
          name: 'Java',
          pros: ['企业级', '生态丰富', '性能优秀'],
          cons: ['冗长语法', '内存占用大'],
          suitableFor: ['企业应用', '大型系统', '金融系统'],
          maturity: 'very_high',
          community: 'excellent',
          performance: 'excellent'
        },
        {
          name: 'Python',
          pros: ['简洁语法', 'AI/ML生态', '快速原型'],
          cons: ['性能较慢', 'GIL限制'],
          suitableFor: ['数据分析', '机器学习', '脚本应用'],
          maturity: 'high',
          community: 'excellent',
          performance: 'fair'
        },
        {
          name: 'Go',
          pros: ['高并发', '快速编译', '简洁设计'],
          cons: ['生态较新', '泛型支持弱'],
          suitableFor: ['系统软件', '云原生', '微服务'],
          maturity: 'medium',
          community: 'good',
          performance: 'excellent'
        }
      ])
      
      // 数据库
      this.technologyMatrix.set('databases', [
        {
          name: 'PostgreSQL',
          type: 'relational',
          pros: ['ACID支持', '功能丰富', '扩展性好'],
          cons: ['复杂查询优化难'],
          suitableFor: ['复杂查询', '事务处理', '数据完整性'],
          scalability: 'vertical',
          consistency: 'strong'
        },
        {
          name: 'MongoDB',
          type: 'document',
          pros: ['灵活架构', '水平扩展', 'JSON原生'],
          cons: ['一致性较弱', '内存占用大'],
          suitableFor: ['快速开发', '灵活数据', '内容管理'],
          scalability: 'horizontal',
          consistency: 'eventual'
        },
        {
          name: 'Redis',
          type: 'key-value',
          pros: ['极高性能', '数据结构丰富', '持久化'],
          cons: ['内存限制', '单线程模型'],
          suitableFor: ['缓存', '会话存储', '实时计算'],
          scalability: 'horizontal',
          consistency: 'strong'
        }
      ])
      
      // 消息队列
      this.technologyMatrix.set('message_queues', [
        {
          name: 'RabbitMQ',
          pros: ['功能丰富', '可靠性高', '管理界面'],
          cons: ['性能中等', '集群复杂'],
          suitableFor: ['企业集成', '复杂路由', '可靠消息'],
          throughput: 'medium',
          latency: 'low'
        },
        {
          name: 'Apache Kafka',
          pros: ['高吞吐', '持久化', '流处理'],
          cons: ['复杂度高', '延迟较高'],
          suitableFor: ['大数据', '流处理', '事件溯源'],
          throughput: 'very_high',
          latency: 'medium'
        }
      ])
    }
    
    // 选择技术栈
    selectTechnologyStack(requirements, architecture, constraints) {
      const selection = {
        programming_language: null,
        database: [],
        message_queue: null,
        caching: null,
        monitoring: null,
        reasoning: []
      }
      
      // 选择编程语言
      selection.programming_language = this.selectProgrammingLanguage(requirements, constraints)
      selection.reasoning.push(`选择 ${selection.programming_language.name}: ${selection.programming_language.reason}`)
      
      // 选择数据库
      selection.database = this.selectDatabases(requirements, architecture)
      selection.database.forEach(db => {
        selection.reasoning.push(`选择 ${db.name}: ${db.reason}`)
      })
      
      // 选择消息队列
      if (architecture.pattern === 'microservices') {
        selection.message_queue = this.selectMessageQueue(requirements)
        selection.reasoning.push(`选择 ${selection.message_queue.name}: ${selection.message_queue.reason}`)
      }
      
      // 选择缓存
      selection.caching = { name: 'Redis', reason: '高性能缓存需求' }
      selection.reasoning.push(`选择 ${selection.caching.name}: ${selection.caching.reason}`)
      
      return selection
    }
    
    selectProgrammingLanguage(requirements, constraints) {
      const languages = this.technologyMatrix.get('programming_languages')
      
      // 技术栈约束
      const techConstraint = constraints.find(c => c.type === 'technology')
      if (techConstraint && techConstraint.description.includes('Node.js')) {
        return {
          ...languages.find(l => l.name === 'Node.js'),
          reason: '项目技术栈约束'
        }
      }
      
      // 性能要求
      const performanceReq = requirements.nonFunctional?.performance
      if (performanceReq && this.parseResponseTime(performanceReq.responseTime) < 100) {
        return {
          ...languages.find(l => l.name === 'Go'),
          reason: '高性能要求'
        }
      }
      
      // 默认选择
      return {
        ...languages.find(l => l.name === 'Node.js'),
        reason: '快速开发和JavaScript生态优势'
      }
    }
    
    selectDatabases(requirements, architecture) {
      const databases = this.technologyMatrix.get('databases')
      const selection = []
      
      // 主数据库
      if (requirements.nonFunctional?.reliability?.dataConsistency === 'strong') {
        selection.push({
          ...databases.find(db => db.name === 'PostgreSQL'),
          role: 'primary',
          reason: '强一致性要求'
        })
      } else {
        selection.push({
          ...databases.find(db => db.name === 'MongoDB'),
          role: 'primary',
          reason: '灵活数据模型和水平扩展'
        })
      }
      
      // 缓存数据库
      selection.push({
        ...databases.find(db => db.name === 'Redis'),
        role: 'cache',
        reason: '高性能缓存和会话存储'
      })
      
      return selection
    }
    
    selectMessageQueue(requirements) {
      const queues = this.technologyMatrix.get('message_queues')
      
      const throughput = this.parseThroughput(requirements.nonFunctional?.performance?.throughput)
      
      if (throughput > 10000) {
        return {
          ...queues.find(q => q.name === 'Apache Kafka'),
          reason: '高吞吐量要求'
        }
      }
      
      return {
        ...queues.find(q => q.name === 'RabbitMQ'),
        reason: '企业级可靠性和功能丰富'
      }
    }
    
    parseResponseTime(responseTimeStr) {
      if (!responseTimeStr) return 1000
      
      const match = responseTimeStr.match(/(\d+)/)
      return match ? parseInt(match[1]) : 1000
    }
    
    parseThroughput(throughputStr) {
      if (!throughputStr) return 1000
      
      const match = throughputStr.match(/(\d+)/)
      return match ? parseInt(match[1]) : 1000
    }
  }
  
  // 系统设计主流程
  async designSystem(projectSpec) {
    console.log('开始系统设计流程...')
    
    const design = {
      id: this.generateDesignId(),
      timestamp: new Date(),
      projectSpec,
      requirements: null,
      architecture: null,
      technologyStack: null,
      capacityPlan: null,
      performanceOptimization: null,
      reliabilityPlan: null
    }
    
    try {
      // 1. 需求分析
      console.log('1. 分析需求...')
      design.requirements = this.requirementAnalyzer.generateRequirementDocument()
      
      // 2. 架构设计
      console.log('2. 设计架构...')
      const patternAnalysis = this.architectureDesigner.selectArchitecturePattern(
        design.requirements,
        projectSpec.constraints || []
      )
      
      const selectedPattern = patternAnalysis.recommendedPatterns[0]?.pattern || 'monolith'
      design.architecture = this.architectureDesigner.designSystemArchitecture(
        selectedPattern,
        design.requirements
      )
      
      // 3. 技术选型
      console.log('3. 选择技术栈...')
      design.technologyStack = this.technologySelector.selectTechnologyStack(
        design.requirements,
        design.architecture,
        projectSpec.constraints || []
      )
      
      // 4. 容量规划
      console.log('4. 容量规划...')
      design.capacityPlan = this.capacityPlanner.createCapacityPlan(
        design.requirements,
        design.architecture
      )
      
      // 5. 性能优化
      console.log('5. 性能优化策略...')
      design.performanceOptimization = this.performanceOptimizer.createOptimizationPlan(
        design.requirements,
        design.architecture,
        design.technologyStack
      )
      
      // 6. 可靠性设计
      console.log('6. 可靠性设计...')
      design.reliabilityPlan = this.reliabilityEngineer.createReliabilityPlan(
        design.requirements,
        design.architecture
      )
      
      console.log('系统设计完成')
      
      return design
      
    } catch (error) {
      console.error('系统设计失败:', error)
      throw error
    }
  }
  
  generateDesignId() {
    return `design_${Date.now()}_${Math.random().toString(36).substr(2, 8)}`
  }
  
  // 生成设计文档
  generateDesignDocument(design) {
    return {
      executiveSummary: this.generateExecutiveSummary(design),
      requirements: design.requirements,
      architecture: this.generateArchitectureDocument(design.architecture),
      technologyStack: design.technologyStack,
      capacityPlanning: design.capacityPlan,
      performanceStrategy: design.performanceOptimization,
      reliabilityStrategy: design.reliabilityPlan,
      implementationPlan: this.generateImplementationPlan(design),
      riskAssessment: this.generateRiskAssessment(design)
    }
  }
  
  generateExecutiveSummary(design) {
    return {
      projectOverview: `采用${design.architecture.pattern}架构模式的系统设计`,
      keyDecisions: [
        `架构模式: ${design.architecture.pattern}`,
        `主要技术: ${design.technologyStack.programming_language.name}`,
        `数据库: ${design.technologyStack.database.map(db => db.name).join(', ')}`,
        `预计容量: ${design.capacityPlan?.estimatedCapacity || '待评估'}`
      ],
      estimatedTimeline: this.estimateImplementationTimeline(design),
      budgetConsiderations: this.estimateBudget(design)
    }
  }
  
  generateArchitectureDocument(architecture) {
    return {
      overview: `${architecture.pattern}架构`,
      components: architecture.components,
      dataFlow: architecture.dataFlow,
      integrations: architecture.integrationPoints,
      deploymentStrategy: architecture.deploymentModel,
      scalingStrategy: architecture.scalingStrategy
    }
  }
  
  estimateImplementationTimeline(design) {
    const baselineWeeks = {
      monolith: 12,
      microservices: 24,
      serverless: 8
    }
    
    const complexityMultiplier = design.requirements.summary.complexityDistribution.high * 0.5 + 1
    const baseline = baselineWeeks[design.architecture.pattern] || 16
    
    return Math.ceil(baseline * complexityMultiplier)
  }
  
  estimateBudget(design) {
    // 简化的预算估算
    const teamCost = 10000 // 每周团队成本
    const timeline = this.estimateImplementationTimeline(design)
    const infrastructureCost = 5000 // 基础设施成本
    
    return {
      development: teamCost * timeline,
      infrastructure: infrastructureCost,
      total: teamCost * timeline + infrastructureCost,
      currency: 'USD'
    }
  }
  
  generateImplementationPlan(design) {
    const phases = []
    
    // MVP阶段
    phases.push({
      phase: 1,
      name: 'MVP开发',
      duration: '6-8周',
      deliverables: ['核心功能', '基础架构', 'MVP部署'],
      requirements: design.requirements.functional.filter(req => req.priority === 'high')
    })
    
    // 功能完善阶段
    phases.push({
      phase: 2,
      name: '功能完善',
      duration: '4-6周',
      deliverables: ['次要功能', '性能优化', '用户体验'],
      requirements: design.requirements.functional.filter(req => req.priority === 'medium')
    })
    
    // 上线准备阶段
    phases.push({
      phase: 3,
      name: '上线准备',
      duration: '2-4周',
      deliverables: ['生产部署', '监控告警', '文档完善'],
      requirements: design.requirements.functional.filter(req => req.priority === 'low')
    })
    
    return phases
  }
  
  generateRiskAssessment(design) {
    const risks = []
    
    // 技术风险
    if (design.architecture.pattern === 'microservices') {
      risks.push({
        category: 'technical',
        risk: '微服务复杂度',
        impact: 'high',
        probability: 'medium',
        mitigation: '充分的服务治理和监控'
      })
    }
    
    // 性能风险
    if (design.requirements.nonFunctional.performance.responseTime.includes('< 100ms')) {
      risks.push({
        category: 'performance',
        risk: '极高性能要求',
        impact: 'high',
        probability: 'medium',
        mitigation: '充分的性能测试和优化'
      })
    }
    
    // 团队风险
    risks.push({
      category: 'team',
      risk: '技术栈学习曲线',
      impact: 'medium',
      probability: 'low',
      mitigation: '技术培训和知识分享'
    })
    
    return risks
  }
}

// 使用示例
async function demonstrateSystemDesign() {
  console.log('=== 系统设计演示 ===')
  
  const framework = new SystemDesignFramework()
  
  // 项目规格
  const projectSpec = {
    userStories: [
      {
        title: '用户注册',
        description: '用户可以通过邮箱注册账户',
        priority: 'high',
        acceptanceCriteria: ['邮箱验证', '密码强度检查'],
        dependencies: []
      },
      {
        title: '用户登录',
        description: '用户可以使用邮箱和密码登录',
        priority: 'high',
        acceptanceCriteria: ['认证成功', '会话管理'],
        dependencies: ['用户注册']
      },
      {
        title: '产品浏览',
        description: '用户可以浏览产品目录',
        priority: 'high',
        acceptanceCriteria: ['分页显示', '搜索过滤'],
        dependencies: []
      },
      {
        title: '购物车管理',
        description: '用户可以添加商品到购物车',
        priority: 'medium',
        acceptanceCriteria: ['添加商品', '数量调整', '删除商品'],
        dependencies: ['用户登录', '产品浏览']
      },
      {
        title: '订单结算',
        description: '用户可以提交订单并支付',
        priority: 'high',
        acceptanceCriteria: ['订单生成', '支付处理', '库存扣减'],
        dependencies: ['购物车管理']
      }
    ],
    nonFunctionalRequirements: {
      performance: {
        responseTime: '< 200ms',
        throughput: '5000 req/s',
        concurrency: 10000
      },
      scalability: {
        userLoad: '100k users',
        dataVolume: '10TB',
        growthRate: '100% yearly'
      },
      availability: {
        uptime: '99.9%',
        mtbf: '720 hours',
        mttr: '2 hours'
      }
    },
    constraints: [
      {
        type: 'budget',
        description: '预算限制: $500k',
        impact: 'high'
      },
      {
        type: 'timeline',
        description: '时间约束: 6个月',
        impact: 'high'
      },
      {
        type: 'team',
        description: '团队规模: 8-12人',
        impact: 'medium'
      }
    ]
  }
  
  // 执行系统设计
  const design = await framework.designSystem(projectSpec)
  
  // 生成设计文档
  const designDocument = framework.generateDesignDocument(design)
  
  console.log('设计摘要:')
  console.log('- 架构模式:', design.architecture.pattern)
  console.log('- 组件数量:', design.architecture.components.length)
  console.log('- 技术选型:', design.technologyStack.programming_language.name)
  console.log('- 预估时间:', designDocument.executiveSummary.estimatedTimeline, '周')
  console.log('- 预估预算:', designDocument.executiveSummary.budgetConsiderations.total, 'USD')
  
  return { framework, design, designDocument }
}

module.exports = {
  SystemDesignFramework
}

📚 最佳实践总结 ​

  1. 需求驱动设计：基于功能和非功能需求进行架构设计
  2. 架构模式选择：根据系统规模和复杂度选择合适的架构模式
  3. 技术选型原则：平衡性能、成本、团队技能和生态成熟度
  4. 容量规划：基于预期负载进行系统容量设计
  5. 性能优化：从架构层面考虑性能优化策略
  6. 可靠性设计：内置容错、监控和恢复机制
  7. 渐进式实施：分阶段实施降低风险
  8. 持续演进：设计支持未来扩展和演进的架构

通过掌握系统设计方法论，您将能够设计出满足业务需求的大规模系统架构。