104 lines
3.3 KiB
TypeScript
104 lines
3.3 KiB
TypeScript
/** 代理核心：鉴权透传、请求转发、SSE 流式透传与错误映射。
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* 照壁不拥有业务规则（service-boundaries.md §3）：能否看到的语义一律来自灵台；
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* 这里只做传输与形状处理——透传凭证/幂等/续传头，流式响应禁缓冲直通。
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*/
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import { Readable } from "node:stream";
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import type { FastifyReply, FastifyRequest } from "fastify";
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/** 需要原样透传的请求头（小写）。 */
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const FORWARD_REQUEST_HEADERS = [
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"authorization",
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"content-type",
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"accept",
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"idempotency-key",
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"last-event-id",
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"x-trace-id",
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] as const;
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/** 需要透传的响应头（SSE 关键头由流式分支显式设置）。 */
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const FORWARD_RESPONSE_HEADERS = ["content-type", "x-trace-id", "retry-after"] as const;
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export interface UpstreamError {
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statusCode: number;
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code: string;
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message: string;
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}
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/** 判定上游响应是否为 SSE 流。 */
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function isEventStream(contentType: string | null): boolean {
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return (contentType ?? "").includes("text/event-stream");
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}
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export async function proxyRequest(
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req: FastifyRequest,
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reply: FastifyReply,
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backendUrl: string,
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): Promise<void> {
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const headers: Record<string, string> = {};
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for (const name of FORWARD_REQUEST_HEADERS) {
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const value = req.headers[name];
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if (value != null) {
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headers[name] = Array.isArray(value) ? value.join(", ") : value;
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}
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}
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const method = req.method;
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const body = method === "GET" || method === "HEAD" ? undefined : (req.body as Buffer);
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let upstream: Response;
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try {
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upstream = await fetch(`${backendUrl}${req.url}`, {
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method,
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headers,
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body: body && body.length > 0 ? new Uint8Array(body) : undefined,
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redirect: "manual",
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});
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} catch (err) {
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// 上游不可达：HJ-3001（API 契约 §5 错误结构）
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req.log.warn({ err: String(err) }, "上游不可达");
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await reply.code(502).send({
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error: { code: "HJ-3001", message: "上游服务不可达", request_id: req.id },
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});
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return;
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}
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if (upstream.body === null) {
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await writeBuffered(reply, upstream);
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return;
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}
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if (isEventStream(upstream.headers.get("content-type"))) {
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writeEventStream(req, reply, upstream);
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return;
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}
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await writeBuffered(reply, upstream);
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}
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async function writeBuffered(reply: FastifyReply, upstream: Response): Promise<void> {
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for (const name of FORWARD_RESPONSE_HEADERS) {
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const value = upstream.headers.get(name);
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if (value != null) {
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reply.header(name, value);
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}
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}
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const payload = Buffer.from(await upstream.arrayBuffer());
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await reply.code(upstream.status).send(payload.length > 0 ? payload : null);
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}
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function writeEventStream(req: FastifyRequest, reply: FastifyReply, upstream: Response): void {
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// 禁缓冲直通：hijack 后绕过 Fastify 序列化，逐块写底层连接
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reply.hijack();
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const raw = reply.raw;
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raw.writeHead(upstream.status, {
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"content-type": upstream.headers.get("content-type") ?? "text/event-stream; charset=utf-8",
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"cache-control": "no-cache",
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"x-accel-buffering": "no",
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});
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const nodeStream = Readable.fromWeb(upstream.body as Parameters<typeof Readable.fromWeb>[0]);
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nodeStream.on("error", (err) => {
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req.log.warn({ err: String(err) }, "上游流中断");
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raw.end();
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});
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nodeStream.pipe(raw);
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}
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