Snowz
07d9afdce5
当 mShots 返回无效图片或失败时，自动降级尝试使用 thum.io 获取截图。主要修改包括： - 新增 fallback 请求处理逻辑 - 扩展缓存元数据记录来源信息 - 在响应头中添加 X-Source 标识备用接口
340 lines
11 KiB
JavaScript
340 lines
11 KiB
JavaScript
const express = require('express');
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const axios = require('axios');
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const fs = require('fs');
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const path = require('path');
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const crypto = require('crypto');
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const net = require('net');
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require('dotenv').config();
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const app = express();
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const PORT = Number(process.env.PORT) || 11489;
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const UPSTREAM_HOST = 'https://s0.wp.com';
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const FALLBACK_HOST_BASE = 'https://image.thum.io/get/width/1024/crop/768/noanimate';
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const CACHE_DIR = path.join(process.cwd(), 'cache');
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fs.mkdirSync(CACHE_DIR, { recursive: true });
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/**
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* 计算 SHA1 哈希
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* @param {string} input
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* @returns {string}
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*/
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function sha1(input) {
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return crypto.createHash('sha1').update(input).digest('hex');
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}
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/**
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* 获取缓存文件路径
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* @param {string} key
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* @returns {{data: string, meta: string}}
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*/
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function getCachePaths(key) {
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return {
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data: path.join(CACHE_DIR, `${key}.data`),
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meta: path.join(CACHE_DIR, `${key}.json`),
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};
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}
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/**
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* 验证响应是否为有效的图片
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* @param {number} status
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* @param {object} headers
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* @param {any} data
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* @returns {boolean}
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*/
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function isValidImageResponse(status, headers, data) {
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const ct = (headers['content-type'] || '').toLowerCase();
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const lenHeader = headers['content-length'];
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const len = Array.isArray(data) ? data.length : (data?.byteLength || 0);
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const hasPositiveLength = (lenHeader ? parseInt(lenHeader, 10) > 0 : len > 0);
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// 过滤掉 GIF 图片 (通常是 mShots 的 "Generating" 占位图，约 9KB)
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// 我们不缓存这些图片，以便下次请求时能再次尝试获取真实截图
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if (ct.includes('image/gif') && len < 15000) {
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return false;
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}
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return status === 200 && ct.startsWith('image/') && hasPositiveLength;
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}
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/**
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* 检查主机是否开放 443 端口 (简单的 SSL 判断)
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* @param {string} host
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* @returns {Promise<boolean>}
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*/
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function checkPort443(host) {
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return new Promise(resolve => {
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// 默认超时 1.5 秒，避免阻塞太久
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const socket = net.connect(443, host);
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socket.setTimeout(1500);
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socket.on('connect', () => {
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socket.end();
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resolve(true);
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});
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socket.on('error', () => {
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resolve(false);
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});
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socket.on('timeout', () => {
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socket.destroy();
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resolve(false);
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});
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});
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}
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/**
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* 解析目标 URL，支持自动补全协议
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* @param {string} rawPath
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* @returns {Promise<string>}
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*/
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async function resolveTargetUrl(rawPath) {
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// 去除开头的 /
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let target = rawPath.startsWith('/') ? rawPath.slice(1) : rawPath;
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// 如果已经包含协议，直接返回
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if (target.startsWith('http://') || target.startsWith('https://')) {
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return target;
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}
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// 提取主机名
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let host = target.split('/')[0].split('?')[0];
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// 去除端口号（如果存在）
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const colonIndex = host.indexOf(':');
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if (colonIndex !== -1) {
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host = host.substring(0, colonIndex);
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}
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// 尝试检测 SSL
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const isHttps = await checkPort443(host);
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if (!isHttps) {
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console.log(`[protocol-detect] ${host} : 443 port closed or timeout, falling back to HTTP.`);
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}
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return isHttps ? `https://${target}` : `http://${target}`;
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}
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/**
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* 请求上游并处理重试
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* @param {string} upstreamUrl
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* @param {number} tries
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* @returns {Promise<any>}
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*/
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async function fetchUpstreamWithRetry(upstreamUrl, tries = 2) {
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let lastErr = null;
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for (let i = 0; i < tries; i++) {
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try {
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return await axios.get(upstreamUrl, {
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responseType: 'arraybuffer',
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headers: {
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'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120 Safari/537.36',
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'Accept': 'image/avif,image/webp,image/apng,image/*;q=0.8,*/*;q=0.5',
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'Host': 's0.wp.com',
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},
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maxRedirects: 5,
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timeout: 20000,
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// 禁用代理环境变量的干扰
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proxy: false,
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// 明确允许非 2xx 也返回给上层判断
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validateStatus: () => true,
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});
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} catch (err) {
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lastErr = err;
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console.error(`[upstream-error] try=${i + 1} url=${upstreamUrl} msg=${err.message}`);
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// 简单退避
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await new Promise(r => setTimeout(r, 300));
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}
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}
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if (lastErr) throw lastErr;
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}
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/**
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* 请求备用接口 (thum.io)
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* @param {string} targetUrl
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* @returns {Promise<any>}
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*/
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async function fetchFallbackWithRetry(targetUrl) {
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// thum.io 格式: https://image.thum.io/get/<options>/<url>
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const fallbackUrl = `${FALLBACK_HOST_BASE}/${targetUrl}`;
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console.log(`[fallback-request] trying fallback: ${fallbackUrl}`);
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try {
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return await axios.get(fallbackUrl, {
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responseType: 'arraybuffer',
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headers: {
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'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64)',
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},
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timeout: 30000,
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validateStatus: () => true,
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});
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} catch (err) {
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console.error(`[fallback-error] msg=${err.message}`);
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return null;
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}
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}
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/**
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* 核心处理逻辑：检查缓存 -> 回源 -> (失败则) 备用接口 -> 写入缓存 -> 返回响应
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* @param {object} res
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* @param {string} upstreamUrl
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* @param {string} targetUrl
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*/
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async function handleProxyRequest(res, upstreamUrl, targetUrl) {
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const key = sha1(upstreamUrl);
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const { data: dataPath, meta: metaPath } = getCachePaths(key);
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try {
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// 1. 尝试读取缓存
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if (fs.existsSync(dataPath) && fs.existsSync(metaPath)) {
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try {
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const metaRaw = fs.readFileSync(metaPath, 'utf8');
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const meta = JSON.parse(metaRaw);
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if (meta.contentType && meta.contentType.toLowerCase().startsWith('image/')) {
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res.set('Cache-Control', 'public, max-age=315360000, immutable');
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res.type(meta.contentType);
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const stream = fs.createReadStream(dataPath);
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stream.on('error', () => {
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if (!res.headersSent) res.status(500).send('Cache read error');
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});
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return stream.pipe(res);
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}
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} catch (e) {
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// 缓存元数据损坏，忽略，继续回源
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}
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}
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// 2. 回源请求
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const resp = await fetchUpstreamWithRetry(upstreamUrl);
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// 3. 检查响应是否有效
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let finalResp = resp;
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let isFallback = false;
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if (!isValidImageResponse(resp.status, resp.headers, resp.data)) {
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console.log(`[upstream-invalid] url=${upstreamUrl} status=${resp.status} len=${resp.data.byteLength}, trying fallback...`);
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const fallbackResp = await fetchFallbackWithRetry(targetUrl);
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if (fallbackResp && isValidImageResponse(fallbackResp.status, fallbackResp.headers, fallbackResp.data)) {
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console.log(`[fallback-success] url=${targetUrl}`);
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finalResp = fallbackResp;
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isFallback = true;
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} else {
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console.log(`[fallback-failed] url=${targetUrl}, returning original response`);
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}
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}
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// 4. 仅缓存有效图片 (无论是回源还是备用)
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if (isValidImageResponse(finalResp.status, finalResp.headers, finalResp.data)) {
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const contentType = finalResp.headers['content-type'] || 'image/jpeg';
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const meta = {
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url: isFallback ? `fallback:${targetUrl}` : upstreamUrl,
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contentType,
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size: finalResp.data.byteLength,
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createdAt: new Date().toISOString(),
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source: isFallback ? 'thum.io' : 'mshots'
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};
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try {
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fs.writeFileSync(dataPath, finalResp.data);
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fs.writeFileSync(metaPath, JSON.stringify(meta));
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} catch (e) {
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// 写盘失败也继续返回
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}
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res.type(contentType);
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res.set('Cache-Control', 'public, max-age=315360000, immutable');
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if (isFallback) {
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res.set('X-Source', 'fallback-thum.io');
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}
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return res.send(finalResp.data);
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}
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// 5. 非图片或非200：兜底策略
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// 若本地已有有效缓存（可能是旧的但有效），优先返回缓存
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if (fs.existsSync(dataPath) && fs.existsSync(metaPath)) {
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try {
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const metaRaw = fs.readFileSync(metaPath, 'utf8');
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const meta = JSON.parse(metaRaw);
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if (meta.contentType && meta.contentType.toLowerCase().startsWith('image/')) {
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res.set('Cache-Control', 'public, max-age=315360000, immutable');
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res.type(meta.contentType);
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const stream = fs.createReadStream(dataPath);
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stream.on('error', () => {
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if (!res.headersSent) res.status(500).send('Cache read error');
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});
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return stream.pipe(res);
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}
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} catch (_) {}
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}
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// 否则透传上游响应
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res.status(resp.status);
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if (resp.headers['content-type']) res.type(resp.headers['content-type']);
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return res.send(resp.data);
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} catch (err) {
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// 5. 回源彻底失败
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// 若本地有缓存可兜底
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if (fs.existsSync(dataPath) && fs.existsSync(metaPath)) {
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try {
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const metaRaw = fs.readFileSync(metaPath, 'utf8');
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const meta = JSON.parse(metaRaw);
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if (meta.contentType && meta.contentType.toLowerCase().startsWith('image/')) {
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res.set('Cache-Control', 'public, max-age=315360000, immutable');
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res.type(meta.contentType);
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const stream = fs.createReadStream(dataPath);
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stream.on('error', () => {
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if (!res.headersSent) res.status(500).send('Cache read error');
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});
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return stream.pipe(res);
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}
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} catch (_) {}
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}
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console.error(`[upstream-failed] url=${upstreamUrl} err=${err.message}`);
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return res.status(502).type('text/plain').send('Upstream error');
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}
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}
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// 反代 mShots，路径 /mshots/v1/...
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app.use('/mshots/v1', async (req, res) => {
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if (req.method !== 'GET') {
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return res.status(405).type('text/plain').send('Method Not Allowed');
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}
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// 这里的 req.originalUrl 包含 /mshots/v1 前缀
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// 我们假设用户可能访问 /mshots/v1/www.baidu.com
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// 需要提取出后面的部分进行解析
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const prefix = '/mshots/v1';
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let pathPart = req.originalUrl;
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if (pathPart.startsWith(prefix)) {
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pathPart = pathPart.slice(prefix.length);
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}
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// 解析目标 URL（补全协议）
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const targetUrl = await resolveTargetUrl(pathPart);
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// 拼接完整上游 URL
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const upstreamUrl = UPSTREAM_HOST + '/mshots/v1/' + targetUrl;
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return handleProxyRequest(res, upstreamUrl, targetUrl);
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});
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// 根路径处理：/https://example.com 或 /www.baidu.com
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app.use(async (req, res) => {
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if (req.method !== 'GET') {
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return res.status(405).type('text/plain').send('Method Not Allowed');
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}
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if (req.path === '/') {
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return res.type('text/plain').send('mShots proxy is running. Try /https://www.baidu.com or /www.baidu.com');
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}
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// 解析目标 URL（补全协议）
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const targetUrl = await resolveTargetUrl(req.originalUrl);
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// 拼接完整上游 URL
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const upstreamUrl = UPSTREAM_HOST + '/mshots/v1/' + targetUrl;
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return handleProxyRequest(res, upstreamUrl, targetUrl);
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});
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// 简单根路由健康检查
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// 根路径健康由上面的 app.use 处理
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app.listen(PORT, () => {
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console.log(`Proxy running at http://localhost:${PORT}`);
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}); |