feat: add Pylon health relay for remote service health checks
DashCaddy Pylon is a lightweight probe agent that runs on remote
networks to relay health checks for services the main DashCaddy
instance can't reach directly (e.g., .sami domains, LAN IPs).
- Standalone zero-dependency Node.js script (pylon/dashcaddy-pylon.js)
- Optional API key auth, HEAD→GET fallback, batch probe support
- Health routes now try direct check first, fall back to pylon relay
- New endpoints: /health/probe (act as pylon), /health/pylon (status)
- Config: add "pylon": { "url": "...", "key": "..." } to config.json
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
232
dashcaddy-api/pylon/dashcaddy-pylon.js
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232
dashcaddy-api/pylon/dashcaddy-pylon.js
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#!/usr/bin/env node
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/**
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* DashCaddy Pylon — Lightweight Health Relay Agent
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*
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* Runs on a remote network to relay health checks for services
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* that the main DashCaddy instance can't reach directly.
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*
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* Zero dependencies — uses only Node.js built-ins.
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*
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* Usage:
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* node dashcaddy-pylon.js # port 3002, no auth
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* PYLON_PORT=3002 PYLON_KEY=secret node dashcaddy-pylon.js
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*
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* Endpoints:
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* GET /probe?url=<url> Health check a URL (returns status)
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* GET /health Pylon's own health
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* GET /info Pylon metadata
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*/
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const http = require('http');
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const https = require('https');
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const { URL } = require('url');
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const os = require('os');
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const PORT = parseInt(process.env.PYLON_PORT || '3002', 10);
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const API_KEY = process.env.PYLON_KEY || '';
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const PROBE_TIMEOUT = parseInt(process.env.PYLON_TIMEOUT || '8000', 10);
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const PYLON_NAME = process.env.PYLON_NAME || os.hostname();
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function json(res, status, data) {
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res.writeHead(status, { 'Content-Type': 'application/json' });
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res.end(JSON.stringify(data));
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}
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function probe(targetUrl) {
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return new Promise((resolve) => {
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let parsed;
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try {
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parsed = new URL(targetUrl);
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} catch (e) {
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return resolve({ status: 'error', reason: 'Invalid URL', url: targetUrl });
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}
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const mod = parsed.protocol === 'https:' ? https : http;
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const start = Date.now();
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const req = mod.request({
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hostname: parsed.hostname,
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port: parsed.port || (parsed.protocol === 'https:' ? 443 : 80),
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path: parsed.pathname + parsed.search,
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method: 'HEAD',
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timeout: PROBE_TIMEOUT,
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rejectUnauthorized: false,
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}, (res) => {
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// Consume the response so the socket is freed
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res.resume();
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const ms = Date.now() - start;
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// HEAD returned 501/405 — retry with GET
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if (res.statusCode === 501 || res.statusCode === 405) {
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const getReq = mod.request({
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hostname: parsed.hostname,
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port: parsed.port || (parsed.protocol === 'https:' ? 443 : 80),
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path: parsed.pathname + parsed.search,
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method: 'GET',
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timeout: PROBE_TIMEOUT,
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rejectUnauthorized: false,
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}, (getRes) => {
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getRes.resume();
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resolve({
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status: getRes.statusCode < 500 ? 'healthy' : 'unhealthy',
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statusCode: getRes.statusCode,
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responseTime: Date.now() - start,
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url: targetUrl,
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checkedAt: new Date().toISOString(),
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});
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});
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getReq.on('error', (e) => resolve({ status: 'unhealthy', reason: e.message, responseTime: Date.now() - start, url: targetUrl, checkedAt: new Date().toISOString() }));
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getReq.on('timeout', () => { getReq.destroy(); resolve({ status: 'unhealthy', reason: 'Timeout', responseTime: Date.now() - start, url: targetUrl, checkedAt: new Date().toISOString() }); });
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getReq.end();
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return;
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}
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const healthy = res.statusCode < 500;
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resolve({
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status: healthy ? 'healthy' : 'unhealthy',
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statusCode: res.statusCode,
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responseTime: ms,
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url: targetUrl,
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checkedAt: new Date().toISOString(),
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});
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});
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req.on('error', (err) => {
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// HEAD not supported — retry with GET
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if (err.code === 'ERR_HTTP_INVALID_STATUS_CODE' || err.message?.includes('HEAD')) {
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const getReq = mod.request({
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hostname: parsed.hostname,
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port: parsed.port || (parsed.protocol === 'https:' ? 443 : 80),
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path: parsed.pathname + parsed.search,
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method: 'GET',
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timeout: PROBE_TIMEOUT,
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rejectUnauthorized: false,
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}, (getRes) => {
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getRes.resume();
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const ms = Date.now() - start;
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resolve({
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status: getRes.statusCode < 500 ? 'healthy' : 'unhealthy',
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statusCode: getRes.statusCode,
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responseTime: ms,
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url: targetUrl,
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checkedAt: new Date().toISOString(),
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});
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});
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getReq.on('error', (getErr) => {
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resolve({
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status: 'unhealthy',
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reason: getErr.message,
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responseTime: Date.now() - start,
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url: targetUrl,
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checkedAt: new Date().toISOString(),
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});
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});
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getReq.on('timeout', () => {
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getReq.destroy();
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resolve({
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status: 'unhealthy',
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reason: 'Timeout',
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responseTime: Date.now() - start,
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url: targetUrl,
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checkedAt: new Date().toISOString(),
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});
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});
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getReq.end();
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return;
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}
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resolve({
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status: 'unhealthy',
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reason: err.message,
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responseTime: Date.now() - start,
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url: targetUrl,
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checkedAt: new Date().toISOString(),
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});
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});
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req.on('timeout', () => {
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req.destroy();
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resolve({
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status: 'unhealthy',
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reason: 'Timeout',
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responseTime: Date.now() - start,
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url: targetUrl,
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checkedAt: new Date().toISOString(),
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});
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});
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req.end();
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});
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}
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const server = http.createServer(async (req, res) => {
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const url = new URL(req.url, `http://localhost:${PORT}`);
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// API key check
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if (API_KEY) {
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const provided = url.searchParams.get('key') || req.headers['x-pylon-key'];
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if (provided !== API_KEY) {
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return json(res, 401, { error: 'Invalid API key' });
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}
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}
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// Routes
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if (url.pathname === '/health') {
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return json(res, 200, { status: 'ok', pylon: PYLON_NAME, uptime: process.uptime() });
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}
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if (url.pathname === '/info') {
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return json(res, 200, {
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pylon: PYLON_NAME,
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hostname: os.hostname(),
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platform: os.platform(),
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uptime: process.uptime(),
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version: '1.0.0',
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});
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}
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if (url.pathname === '/probe') {
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const targetUrl = url.searchParams.get('url');
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if (!targetUrl) {
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return json(res, 400, { error: 'Missing ?url= parameter' });
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}
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// Block obviously dangerous URLs (localhost probing from the pylon itself)
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const parsed = new URL(targetUrl);
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if (parsed.hostname === 'localhost' && parsed.port === String(PORT)) {
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return json(res, 400, { error: 'Cannot probe self' });
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}
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const result = await probe(targetUrl);
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return json(res, 200, result);
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}
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// Batch probe: POST /probe with JSON body { urls: [...] }
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if (url.pathname === '/probe' && req.method === 'POST') {
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let body = '';
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req.on('data', c => body += c);
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req.on('end', async () => {
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try {
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const { urls } = JSON.parse(body);
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if (!Array.isArray(urls) || urls.length === 0) {
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return json(res, 400, { error: 'Missing urls array' });
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}
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if (urls.length > 50) {
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return json(res, 400, { error: 'Max 50 URLs per batch' });
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}
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const results = await Promise.all(urls.map(u => probe(u)));
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return json(res, 200, { results });
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} catch (e) {
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return json(res, 400, { error: 'Invalid JSON body' });
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}
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});
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return;
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}
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json(res, 404, { error: 'Not found' });
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});
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server.listen(PORT, '0.0.0.0', () => {
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console.log(`[Pylon] ${PYLON_NAME} listening on port ${PORT}`);
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if (API_KEY) console.log('[Pylon] API key authentication enabled');
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});
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