# 构建 Cloudflare Worker API 代理的提示

> 复制粘贴 AI 提示，构建一个 Cloudflare Worker，用于代理外部 API 调用并限速、添加认证头以及缓存响应。

**Type:** Prompt  
**Tools:** Cursor, Claude Code, Codex, Windsurf  
**Stack:** Cloudflare, TypeScript  
**Difficulty:** medium  
**Updated:** 2026-06-08

---

使用此提示构建一个 Cloudflare Worker，它位于外部 API 之前，注入认证标头，通过 Workers KV 按 IP 进行速率限制，并缓存响应——这样客户端就永远看不到你的上游 API 密钥。

## 主要提示

```txt title="Main Prompt"
You are building a Cloudflare Worker using TypeScript and the Workers runtime (not Node.js).
The Worker will proxy requests to an upstream API (e.g., OpenAI at https://api.openai.com).

Task: create a production-ready API proxy Worker.

Requirements:
- Use `wrangler` v3 for local dev. Scaffold with `bun create cloudflare@latest` and choose
  "Hello World" Worker with TypeScript.
- Upstream URL: read from a Wrangler secret `UPSTREAM_URL` (string).
- Auth: inject `Authorization: Bearer ${env.UPSTREAM_API_KEY}` on every proxied request,
  where `UPSTREAM_API_KEY` is a Wrangler secret. Never expose this header to the client.
- CORS: allow only origins in `env.ALLOWED_ORIGINS` (comma-separated string secret).
  Return a `403` for disallowed origins. Handle preflight OPTIONS requests.
- Rate limiting: use Workers KV binding `RATE_LIMIT_KV`.
  - Key: `rl:${ip}` where ip is `request.headers.get('CF-Connecting-IP')`.
  - Value: request count for the current UTC minute (TTL = 60 s).
  - Limit: 60 requests/minute per IP. Return `429` with `Retry-After: 60` if exceeded.
- Caching: for GET requests, check `caches.default` before proxying upstream. Cache
  successful responses with `Cache-Control: public, max-age=300`.
- Strip the following headers from the upstream response before returning to the client:
  `x-powered-by`, `server`, `cf-ray`.
- Wrangler config: declare the KV namespace binding and all secrets in `wrangler.toml`.
- Do NOT use Node.js APIs (`fs`, `path`, `Buffer`) — Workers runtime only.

Stop and list all planned files before writing code.
```

## 实现说明

- Cloudflare Workers 接收 `Request` 并返回 `Response`——避免使用 `express` 风格的模式。
- `caches.default` 是 Cloudflare 边缘缓存；仅在生产环境中有效。在本地开发测试中使用 `MINIFLARE_CACHE` 或模拟缓存。
- `CF-Connecting-IP` 由 Cloudflare 注入——从公共互联网无法伪造，但在本地测试时使用硬编码的回退 IP。
- Wrangler 密钥通过 `wrangler secret put UPSTREAM_API_KEY` 设置——切勿将它们存储在 `wrangler.toml` 或已提交的 `.env` 文件中。

## 预期文件变更

```txt
wrangler.toml                  (new)
src/index.ts                   (new — Worker entrypoint)
src/cors.ts                    (new — CORS helper)
src/rate-limit.ts              (new — KV rate limiter)
package.json                   (new)
tsconfig.json                  (new)
.dev.vars                      (new — local dev secrets, gitignored)
.gitignore                     (edited — add .dev.vars)
```

## 验收标准

- `wrangler dev` 启动无错误，并将 `GET /` 代理到上游 URL。
- 一分钟内发送 61 次请求的 IP 在第 61 次请求时收到 `429`。
- 来自未允许来源的请求收到 `403`。
- `Authorization` 标头不出现在响应或任何客户端可见的标头中。
- `wrangler deploy` 成功，Worker 在 `workers.dev` 上运行。

## 测试命令

```bash
wrangler dev &
# test normal proxy
curl http://localhost:8787/ -H "Origin: https://myapp.com"
# test CORS rejection
curl http://localhost:8787/ -H "Origin: https://evil.com"
# test rate limit (requires 61 rapid requests)
for i in $(seq 1 62); do curl -s -o /dev/null -w "%{http_code}\n" http://localhost:8787/; done
```

## 常见 AI 错误

- 使用 `process.env` 而不是传递给 Worker `fetch` 处理程序的 `env` 参数。
- 忘记处理 `OPTIONS` 预检请求，导致 POST/PUT 调用的 CORS 失效。
- 将 `UPSTREAM_API_KEY` 作为普通变量存储在 `wrangler.toml` 中，而不是作为密钥。
- 使用 `node:buffer` 或其他 Node.js 内置模块，这些在 Workers 运行时中不可用。

## 修复提示

```txt title="Fix Prompt"
The Worker fails with a runtime error or leaks the API key. Fix in order:
1. Replace `process.env.X` with `env.X` everywhere — Workers use the `env` handler parameter.
2. Add an OPTIONS handler before the proxy logic that returns the CORS headers with a 204 status.
3. Move `UPSTREAM_API_KEY` from `wrangler.toml` [vars] to a secret: `wrangler secret put UPSTREAM_API_KEY`.
Show only the corrected diff.
```