feat: initial vps-health-api service

Zero-dependency Node.js health endpoint exposing CPU, RAM, disk and
uptime metrics. Bearer token auth, Docker-ready (node:22-alpine).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.env.example

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+PORT=3001
+HEALTH_TOKEN=change-me-to-a-strong-secret

.gitignore

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+node_modules/
+.env
+.env.local

Dockerfile

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+FROM node:22-alpine
+WORKDIR /app
+COPY package.json index.js ./
+EXPOSE 3001
+USER node
+CMD ["node", "index.js"]

index.js

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+const http = require("node:http");
+const os = require("node:os");
+const { execSync } = require("node:child_process");
+
+const PORT = parseInt(process.env.PORT || "3001", 10);
+const TOKEN = process.env.HEALTH_TOKEN;
+
+function readProcStat() {
+  try {
+    const line = execSync("head -1 /proc/stat", { encoding: "utf-8" }).trim();
+    const parts = line.split(/\s+/).slice(1).map(Number);
+    const idle = parts[3] + parts[4];
+    const total = parts.reduce((a, b) => a + b, 0);
+    return { idle, total };
+  } catch {
+    return null;
+  }
+}
+
+function getCpuPercent() {
+  const t1 = readProcStat();
+  if (!t1) return 0;
+  const { idle: idle1, total: total1 } = t1;
+
+  // Sample over 500ms
+  execSync("sleep 0.5");
+
+  const t2 = readProcStat();
+  if (!t2) return 0;
+  const dIdle = t2.idle - idle1;
+  const dTotal = t2.total - total1;
+  if (dTotal === 0) return 0;
+  return Math.round((1 - dIdle / dTotal) * 100);
+}
+
+function getDisk() {
+  try {
+    const out = execSync("df / --output=size,used,avail -B1", {
+      encoding: "utf-8",
+    });
+    const parts = out.trim().split("\n")[1].trim().split(/\s+/).map(Number);
+    const totalGB = +(parts[0] / 1e9).toFixed(1);
+    const usedGB = +(parts[1] / 1e9).toFixed(1);
+    const freeGB = +(parts[2] / 1e9).toFixed(1);
+    const usagePercent = totalGB > 0 ? Math.round((usedGB / totalGB) * 100) : 0;
+    return { totalGB, usedGB, freeGB, usagePercent };
+  } catch {
+    return { totalGB: 0, usedGB: 0, freeGB: 0, usagePercent: 0 };
+  }
+}
+
+function getHealth() {
+  const cpus = os.cpus();
+  const totalMem = os.totalmem();
+  const freeMem = os.freemem();
+  const usedMem = totalMem - freeMem;
+
+  return {
+    timestamp: new Date().toISOString(),
+    hostname: os.hostname(),
+    uptime: Math.floor(os.uptime()),
+    cpu: {
+      model: cpus[0]?.model?.trim() || "unknown",
+      cores: cpus.length,
+      loadAvg: os.loadavg().map((l) => +l.toFixed(2)),
+      usagePercent: getCpuPercent(),
+    },
+    memory: {
+      totalGB: +(totalMem / 1e9).toFixed(1),
+      usedGB: +(usedMem / 1e9).toFixed(1),
+      freeGB: +(freeMem / 1e9).toFixed(1),
+      usagePercent: Math.round((usedMem / totalMem) * 100),
+    },
+    disk: getDisk(),
+  };
+}
+
+const server = http.createServer((req, res) => {
+  res.setHeader("Content-Type", "application/json");
+
+  if (req.url !== "/health" || req.method !== "GET") {
+    res.writeHead(404);
+    res.end(JSON.stringify({ error: "Not found" }));
+    return;
+  }
+
+  if (TOKEN) {
+    const auth = req.headers["authorization"];
+    if (auth !== `Bearer ${TOKEN}`) {
+      res.writeHead(401);
+      res.end(JSON.stringify({ error: "Unauthorized" }));
+      return;
+    }
+  }
+
+  const data = getHealth();
+  res.writeHead(200);
+  res.end(JSON.stringify(data));
+});
+
+server.listen(PORT, () => {
+  console.log(`vps-health-api listening on :${PORT}`);
+});

package.json

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+{
+  "name": "vps-health-api",
+  "version": "1.0.0",
+  "description": "Lightweight VPS health monitoring endpoint",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index.js"
+  }
+}