Do Storage 设计模式

# DO 存储模式与最佳实践 ## 模式迁移 typescript export class MyDurableObject extends DurableObject { constructor(ctx: DurableObjectState, env: Env) { super(ctx, env); this.sql = ctx.storage.sql; // 使用 SQLite 内置的 user_version pragma const ver = this.sql.exec("PRAGMA user_version").one()?.user_version || 0; if (ver === 0) { this.sql.exec(`CREATE TABLE users(id INTEGER PRIMARY KEY, name TEXT)`); this.sql.exec("PRAGMA user_version = 1"); } if (ver === 1) { this.sql.exec(`ALTER TABLE users ADD COLUMN email TEXT`); this.sql.exec("PRAGMA user_version = 2"); } } } ## 内存缓存 typescript export class UserCache extends DurableObject { cache = new Map(); async getUser(id: string): Promise { if (this.cache.has(id)) { const cached = this.cache.get(id); if (cached) return cached; } const user = await this.ctx.storage.get(`user:${id}`); if (user) this.cache.set(id, user); return user; } async updateUser(id: string, data: Partial) { const updated = { ...await this.getUser(id), ...data }; this.cache.set(id, updated); await this.ctx.storage.put(`user:${id}`, updated); return updated; } } ## 速率限制 typescript export class RateLimiter extends DurableObject { async checkLimit(key: string, limit: number, window: number): Promise { const now = Date.now(); this.sql.exec('DELETE FROM requests WHERE key = ? AND timestamp = limit) return false; this.sql.exec('INSERT INTO requests (key, timestamp) VALUES (?, ?)', key, now); return true; } } ## 使用闹钟进行批处理 typescript export class BatchProcessor extends DurableObject { pending: string[] = []; async addItem(item: string) { this.pending.push(item); if (!await this.ctx.storage.getAlarm()) await this.ctx.storage.setAlarm(Date.now() + 5000); } async alarm() { const items = [...this.pending]; this.pending = []; this.sql.exec(`INSERT INTO processed_items (item, timestamp) VALUES ${items.map(() => "(?, ?)").join(", ")}`, ...items.flatMap(item => [item, Date.now()])); } } ## 初始化模式 typescript export class Counter extends DurableObject { value: number;