Surplus brings JSX directly to the real DOM using S.js fine-grained reactivity — no virtual DOM, no diffing, just precise signal-driven updates. But raw rendering precision means nothing if your app is down or your API is silently failing. Vigilmon gives you the visibility layer your production Surplus app needs: continuous HTTP monitoring, heartbeat checks, and instant alerts routed to email or Slack.
What You'll Build
- A health API endpoint for your Surplus application backend
- Vigilmon HTTP monitors for your Surplus SPA and backend API
- A heartbeat for scheduled background tasks
- Alert channels (email and Slack)
- An uptime badge embedded in your Surplus UI
Prerequisites
- A Surplus project (built with the
surplusands-jspackages) - Node.js backend for the health endpoint
- A free Vigilmon account
Step 1: Add a Health Endpoint
Surplus optimizes client-side reactivity; your backend remains a conventional Node service. Add a /health route:
// server.js (Express)
import express from "express";
const app = express();
app.get("/health", async (req, res) => {
const checks = {};
let degraded = false;
// Database check
try {
// await db.query("SELECT 1");
checks.database = "ok";
} catch (err) {
checks.database = `error: ${err.message}`;
degraded = true;
}
// External API check
try {
const response = await fetch("https://api.example.com/ping", {
signal: AbortSignal.timeout(3000),
});
checks.external_api = response.ok ? "ok" : `http_${response.status}`;
} catch (err) {
checks.external_api = "unreachable";
degraded = true;
}
res.status(degraded ? 503 : 200).json({
status: degraded ? "degraded" : "ok",
timestamp: new Date().toISOString(),
checks,
});
});
app.listen(process.env.PORT ?? 3000);
Test it:
curl http://localhost:3000/health | jq .
# {"status":"ok","timestamp":"2026-07-03T...","checks":{"database":"ok","external_api":"ok"}}
Step 2: Configure Vigilmon HTTP Monitors
Log in to Vigilmon → Monitors → New Monitor:
Monitor 1: Surplus SPA (frontend)
| Field | Value |
|---|---|
| URL | https://yourapp.com/ |
| Method | GET |
| Expected status | 200 |
| Expected body | A stable string from your HTML (e.g. <div id="app">) |
| Check interval | 1 minute |
Monitor 2: Backend Health API
| Field | Value |
|---|---|
| URL | https://yourapp.com/health |
| Method | GET |
| Expected status | 200 |
| Check interval | 1 minute |
With both monitors you cover two independent failure classes: the CDN/static serving layer and the backend/data layer.
Step 3: Heartbeat for Background Tasks
S.js computations are synchronous and reactive, but your backend may run scheduled jobs — data sync, cache warming, notification dispatch — that can fail silently. A Vigilmon heartbeat alerts you when the expected ping doesn't arrive.
npm install node-cron
// scheduler.js
import cron from "node-cron";
const VIGILMON_HEARTBEAT_URL = process.env.VIGILMON_HEARTBEAT_URL ?? "";
async function pingHeartbeat() {
if (!VIGILMON_HEARTBEAT_URL) return;
try {
await fetch(VIGILMON_HEARTBEAT_URL, { signal: AbortSignal.timeout(5000) });
} catch {
// Monitoring must never crash the job
}
}
cron.schedule("*/5 * * * *", async () => {
try {
await processDataSync();
await pingHeartbeat();
} catch (err) {
console.error("[scheduler] Data sync failed:", err);
// Vigilmon alerts after the heartbeat window expires with no ping
}
});
async function processDataSync() {
// Your actual sync logic
}
Set up the heartbeat in Vigilmon:
- Monitors → New Heartbeat Monitor
- Set Expected interval to 10 minutes (2× the cron interval)
- Copy the ping URL to your
.env:
VIGILMON_HEARTBEAT_URL=https://vigilmon.online/api/heartbeat/xxxxxxxx
Step 4: Display Uptime Status in Your Surplus UI
Surplus JSX compiles directly to real DOM nodes. Add a status badge component using S.js signals:
// src/StatusBadge.jsx
import S from "s-js";
const BADGE_URL = "https://vigilmon.online/api/badge/your-monitor-id.svg";
const STATUS_URL = "https://vigilmon.online/status/your-monitor-slug";
export function StatusBadge() {
const loaded = S.data(false);
return (
<a
href={STATUS_URL}
target="_blank"
rel="noopener noreferrer"
aria-label="Service uptime status"
style="display:inline-flex;align-items:center"
>
<img
src={BADGE_URL}
alt="Uptime"
width={120}
height={20}
onload={() => loaded(true)}
style={() => `opacity:${loaded() ? 1 : 0};transition:opacity 0.2s`}
/>
</a>
);
}
Mount the badge in your app root:
// src/index.jsx
import S from "s-js";
import { StatusBadge } from "./StatusBadge";
S.root(() => {
document.body.appendChild(
<footer>
<StatusBadge />
</footer>
);
});
Step 5: Set Up Alert Channels
In Vigilmon's Alert Channels settings:
- Alert Channels → Email → add your on-call email
- Attach to both HTTP monitors and the heartbeat
Slack
- Create a Slack Incoming Webhook for
#alerts - Alert Channels → Webhook → paste the URL
- Payload template:
{
"text": "🚨 *{{ monitor.name }}* is DOWN\n{{ monitor.url }}\nStatus: {{ event.status }}\n<https://vigilmon.online|Open Vigilmon>"
}
Step 6: Verify Everything Works
# 1. Health endpoint
curl -s https://yourapp.com/health | jq .
# 2. Break the DB connection string → confirm health returns 503
# Expected: Vigilmon alerts within 2 minutes
# 3. Remove VIGILMON_HEARTBEAT_URL → let the scheduler run without pinging
# Expected: heartbeat alert fires after the grace window
# 4. Vigilmon → "Test Alert" → confirm delivery to Slack/email
Summary
| Monitor | What It Catches | |---|---| | HTTP SPA check | CDN failures, broken static deploys | | HTTP health API | Database, cache, and third-party API failures | | Heartbeat | Scheduler crashes, silent sync failures |
Next Steps
- Create separate monitors for staging vs. production
- Use Vigilmon's response time graphs to spot latency regressions independent of S.js computation performance
- Configure multi-channel alerting: email for low-severity, Slack for critical
Ready to get started? Sign up for Vigilmon free — have your first monitor running in under 5 minutes.