backend-patterns

# 后端开发模式 可扩展服务器端应用的后端架构模式和最佳实践。 ## 何时激活 - 设计 REST 或 GraphQL API 端点 - 实现存储库、服务或控制器层 - 优化数据库查询（N+1、索引、连接池） - 添加缓存（Redis、内存、HTTP 缓存头） - 设置后台作业或异步处理 - 构建 API 的错误处理和验证结构 - 构建中间件（身份验证、日志记录、速率限制） ## API 设计模式 ### RESTful API 结构 ```typescript // PASS：基于资源的 URL GET /api/markets # 列出资源 GET /api/markets/:id # 获取单个资源 POST /api/markets # 创建资源 PUT /api/markets/:id # 替换资源 PATCH /api/markets/:id # 更新资源 DELETE /api/markets/:id # 删除资源 // PASS：用于过滤、排序、分页的查询参数 GET /api/markets?status=active&sort=volume&limit=20&offset=0 ``` ### 存储库模式 ```typescript // 抽象数据访问逻辑 interface MarketRepository { findAll(filters?: MarketFilters): Promise<Market[]> findById(id: string): Promise<Market | null> create(data: CreateMarketDto): Promise<Market> update(id: string, data: UpdateMarketDto): Promise<Market> delete(id: string): Promise<void> } class SupabaseMarketRepository implements MarketRepository { async findAll(filters?: MarketFilters): Promise<Market[]> { let query = supabase.from('markets').select('*') if (filters?.status) { query = query.eq('status', filters.status) } if (filters?.limit) { query = query.limit(filters.limit) } const { data, error } = await query if (error) throw new Error(error.message) return data } // 其他方法... } ``` ### 服务层模式 ```typescript // 与数据访问分离的业务逻辑 class MarketService { constructor(private marketRepo: MarketRepository) {} async searchMarkets(query: string, limit: number = 10): Promise<Market[]> { // 业务逻辑 const embedding = await generateEmbedding(query) const results = await this.vectorSearch(embedding, limit) // 获取完整数据 const markets = await this.marketRepo.findByIds(results.map(r => r.id)) // 按相似度排序 return markets.sort((a, b) => { const scoreA = results.find(r => r.id === a.id)?.score || 0 const scoreB = results.find(r => r.id === b.id)?.score || 0 return scoreA - scoreB }) } private async vectorSearch(embedding: number[], limit: number) { // 向量搜索实现 } } ``` ### 中间件模式 ```typescript // 请求/响应处理管道 export function withAuth(handler: NextApiHandler): NextApiHandler { return async (req, res) => { const token = req.headers.authorization?.replace('Bearer ', '') if (!token) { return res.status(401).json({ error: 'Unauthorized' }) } try { const user = await verifyToken(token) req.user = user return handler(req, res) } catch (error) { return res.status(401).json({ error: 'Invalid token' }) } } } // 使用 export default withAuth(async (req, res) => { // 处理程序可以访问 req.user }) ``` ## 数据库模式 ### 查询优化 ```typescript // PASS：GOOD：仅选择所需列 const { data } = await supabase .from('markets') .select('id, name, status, volume') .eq('status', 'active') .order('volume', { ascending: false }) .limit(10) // FAIL：BAD：选择所有内容 const { data } = await supabase .from('markets') .select('*') ``` ### N+1 查询预防 ```typescript // FAIL：BAD：N+1 查询问题 const markets = await getMarkets() for (const market of markets) { market.creator = await getUser(market.creator_id) // N 个查询 } // PASS：GOOD：批量获取 const markets = await getMarkets() const creatorIds = markets.map(m => m.creator_id) const creators = await getUsers(creatorIds) // 1 个查询 const creatorMap = new Map(creators.map(c => [c.id, c])) markets.forEach(market => { market.creator = creatorMap.get(market.creator_id) }) ``` ### 事务模式 ```typescript async function createMarketWithPosition( marketData: CreateMarketDto, positionData: CreatePositionDto ) { // 使用 Supabase 事务 const { data, error } = await supabase.rpc('create_market_with_position', { market_data: marketData, position_data: positionData }) if (error) throw new Error('Transaction failed') return data } // Supabase 中的 SQL 函数 CREATE OR REPLACE FUNCTION create_market_with_position( market_data jsonb, position_data jsonb ) RETURNS jsonb LANGUAGE plpgsql AS $$ BEGIN -- 自动启动事务 INSERT INTO markets VALUES (market_data); INSERT INTO positions VALUES (position_data); RETURN jsonb_build_object('success', true); EXCEPTION WHEN OTHERS THEN -- 自动回滚 RETURN jsonb_build_object('success', false, 'error', SQLERRM); END; $$; ``` ## 缓存策略 ### Redis 缓存层 ```typescript class CachedMarketRepository implements MarketRepository { constructor( private baseRepo: MarketRepository, private redis: RedisClient ) {} async findById(id: string): Promise<Market | null> { // 首先检查缓存 const cached = await this.redis.get(`market:${id}`) if (cached) { return JSON.parse(cached) } // 缓存未命中 — 从数据库获取 const market = await this.baseRepo.findById(id) if (market) { // 缓存 5 分钟 await this.redis.setex(`market:${id}`, 300, JSON.stringify(market)) } return market } async invalidateCache(id: string): Promise<void> { await this.redis.del(`market:${id}`) } } ``` ### Cache-Aside 模式 ```typescript async function getMarketWithCache(id: string): Promise<Market> { const cacheKey = `market:${id}` // 尝试缓存 const cached = await redis.get(cacheKey) if (cached) return JSON.parse(cached) // 缓存未命中 — 从 DB 获取 const market = await db.markets.findUnique({ where: { id } }) if (!market) throw new Error('Market not found') // 更新缓存 await redis.setex(cacheKey, 300, JSON.stringify(market)) return market } ``` ## 错误处理模式 ### 集中式错误处理程序 ```typescript class ApiError extends Error { constructor( public statusCode: number, public message: string, public isOperational = true ) { super(message) Object.setPrototypeOf(this, ApiError.prototype) } } export function errorHandler(error: unknown, req: Request): Response { if (error instanceof ApiError) { return NextResponse.json({ success: false, error: error.message }, { status: error.statusCode }) } if (error instanceof z.ZodError) { return NextResponse.json({ success: false, error: 'Validation failed', details: error.errors }, { status: 400 }) } // 记录意外错误 console.error('Unexpected error:', error) return NextResponse.json({ success: false, error: 'Internal server error' }, { status: 500 }) } // 使用 export async function GET(request: Request) { try { const data = await fetchData() return NextResponse.json({ success: true, data }) } catch (error) { return errorHandler(error, request) } } ``` ### 指数退避重试 ```typescript async function fetchWithRetry<T>( fn: () => Promise<T>, maxRetries = 3 ): Promise<T> { let lastError: Error for (let i = 0; i < maxRetries; i++) { try { return await fn() } catch (error) { lastError = error as Error if (i < maxRetries - 1) { // 指数退避：1s、2s、4s const delay = Math.pow(2, i) * 1000 await new Promise(resolve => setTimeout(resolve, delay)) } } } throw lastError! } // 使用 const data = await fetchWithRetry(() => fetchFromAPI()) ``` ## 身份验证和授权 ### JWT 令牌验证 ```typescript import jwt from 'jsonwebtoken' interface JWTPayload { userId: string email: string role: 'admin' | 'user' } export function verifyToken(token: string): JWTPayload { try { const payload = jwt.verify(token, process.env.JWT_SECRET!) as JWTPayload return payload } catch (error) { throw new ApiError(401, 'Invalid token') } } export async function requireAuth(request: Request) { const token = request.headers.get('authorization')?.replace('Bearer ', '') if (!token) { throw new ApiError(401, 'Missing authorization token') } return verifyToken(token) } // 在 API 路由中使用 export async function GET(request: Request) { const user = await requireAuth(request) const data = await getDataForUser(user.userId) return NextResponse.json({ success: true, data }) } ``` ### 基于角色的访问控制 ```typescript type Permission = 'read' | 'write' | 'delete' | 'admin' interface User { id: string role: 'admin' | 'moderator' | 'user' } const rolePermissions: Record<User['role'], Permission[]> = { admin: ['read', 'write', 'delete', 'admin'], moderator: ['read', 'write', 'delete'], user: ['read', 'write'] } export function hasPermission(user: User, permission: Permission): boolean { return rolePermissions[user.role].includes(permission) } export function requirePermission(permission: Permission) { return (handler: (request: Request, user: User) => Promise<Response>) => { return async (request: Request) => { const user = await requireAuth(request) if (!hasPermission(user, permission)) { throw new ApiError(403, 'Insufficient permissions') } return handler(request, user) } } } // 使用 - HOF 包装处理程序 export const DELETE = requirePermission('delete')( async (request: Request, user: User) => { // 处理程序接收具有已验证权限的已认证用户 return new Response('Deleted', { status: 200 }) } ) ``` ## 速率限制 ### 简单内存速率限制器 ```typescript class RateLimiter { private requests = new Map<string, number[]>() async checkLimit( identifier: string, maxRequests: number, windowMs: number ): Promise<boolean> { const now = Date.now() const requests = this.requests.get(identifier) || [] // 删除窗口外的旧请求 const recentRequests = requests.filter(time => now - time < windowMs) if (recentRequests.length >= maxRequests) { return false // 超过速率限制 } // 添加当前请求 recentRequests.push(now) this.requests.set(identifier, recentRequests) return true } } const limiter = new RateLimiter() export async function GET(request: Request) { const ip = request.headers.get('x-forwarded-for') || 'unknown' const allowed = await limiter.checkLimit(ip, 100, 60000) // 100 次/分钟 if (!allowed) { return NextResponse.json({ error: 'Rate limit exceeded' }, { status: 429 }) } // 继续处理请求 } ``` ## 后台作业和队列 ### 简单队列模式 ```typescript class JobQueue<T> { private queue: T[] = [] private processing = false async add(job: T): Promise<void> { this.queue.push(job) if (!this.processing) { this.process() } } private async process(): Promise<void> { this.processing = true while (this.queue.length > 0) { const job = this.queue.shift()! try { await this.execute(job) } catch (error) { console.error('Job failed:', error) } } this.processing = false } private async execute(job: T): Promise<void> { // 作业执行逻辑 } } // 用于索引市场的使用 interface IndexJob { marketId: string } const indexQueue = new JobQueue<IndexJob>() export async function POST(request: Request) { const { marketId } = await request.json()