Sinuous is a tiny reactive JavaScript library that keeps things lean — no virtual DOM, a minimal API surface, and a bundle footprint small enough that your app loads in milliseconds. But small bundle size doesn't protect you from downtime. When your API silently returns 503s or a background sync job crashes at 3 AM, Vigilmon is the visibility layer that catches it: continuous HTTP monitoring, heartbeat checks, and instant alerts routed to email or Slack.
What You'll Build
- A health API endpoint for your Sinuous app's backend (Node/Express)
- Vigilmon HTTP monitors for your SPA and backend health route
- A heartbeat for scheduled background tasks
- Alert channels (email and Slack)
- An uptime badge rendered in your Sinuous view
Prerequisites
- A Sinuous project (bundled with Rollup, Vite, or esbuild)
- A Node.js backend to host your health endpoint
- A free Vigilmon account
Step 1: Add a Health Endpoint
Sinuous runs entirely in the browser, so your health endpoint lives on the Node/Express server that serves the SPA or powers its API:
// server.js
import express from "express";
const app = express();
app.get("/health", async (req, res) => {
const checks = {};
let degraded = false;
// Database check
try {
// await db.execute("SELECT 1");
checks.database = "ok";
} catch (err) {
checks.database = `error: ${err.message}`;
degraded = true;
}
// External API check
try {
const resp = await fetch("https://api.stripe.com/v1/", {
signal: AbortSignal.timeout(3000),
});
checks.stripe = resp.status < 500 ? "ok" : `http_${resp.status}`;
} catch {
checks.stripe = "unreachable";
degraded = true;
}
res.status(degraded ? 503 : 200).json({
status: degraded ? "degraded" : "ok",
timestamp: new Date().toISOString(),
checks,
});
});
// Serve Sinuous SPA
app.use(express.static("dist"));
app.listen(process.env.PORT ?? 3000);
Test it:
curl http://localhost:3000/health | jq .
# {"status":"ok","timestamp":"2026-06-29T...","checks":{"database":"ok","stripe":"ok"}}
Step 2: Configure Vigilmon HTTP Monitors
Log in to Vigilmon → Monitors → New Monitor:
Monitor 1: Sinuous SPA
| Field | Value |
|---|---|
| URL | https://yourapp.com/ |
| Method | GET |
| Expected status | 200 |
| Expected body | A stable string from your HTML (e.g. your app's <title>) |
| Check interval | 1 minute |
Monitor 2: Health API
| Field | Value |
|---|---|
| URL | https://yourapp.com/health |
| Method | GET |
| Expected status | 200 |
| Check interval | 1 minute |
Two monitors cover two independent failure classes: the static hosting layer and the backend/data layer.
Step 3: Heartbeat for Background Tasks
Background jobs — data sync, email digests, webhook processing — can fail silently for hours without anyone noticing. A Vigilmon heartbeat fires an alert when the expected ping never arrives.
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] Sync failed:", err);
// No ping → Vigilmon alerts after the grace window
}
});
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 Sinuous UI
Sinuous's observable primitives make it simple to embed a live status badge without any framework overhead:
// src/status-badge.js
import { h, o } from "sinuous";
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 = o(false);
return h(
"a",
{
href: STATUS_URL,
target: "_blank",
rel: "noopener noreferrer",
"aria-label": "Service uptime status",
},
h("img", {
src: BADGE_URL,
alt: "Uptime",
width: 120,
height: 20,
onload: () => loaded(true),
style: () => `opacity:${loaded() ? 1 : 0};transition:opacity 0.2s`,
})
);
}
Mount it in your app footer:
// src/app.js
import { h } from "sinuous";
import { StatusBadge } from "./status-badge.js";
export function App() {
return h("div", null,
h("main", null, /* your routes */),
h("footer", { class: "footer" }, StatusBadge())
);
}
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. Unset VIGILMON_HEARTBEAT_URL → let the scheduler run
# 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 after dependency updates
- 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.