How do you implement a health monitoring dashboard in Node.js?

Question

Accepted Answer

**Health dashboard** — monitor service health and metrics.

```javascript
const promClient = require("prom-client");

// Collect default metrics
promClient.collectDefaultMetrics();

// Custom metrics
const httpRequestDuration = new promClient.Histogram({
    name: "http_request_duration_seconds",
    help: "Duration of HTTP requests",
    labelNames: ["method", "route", "status"],
    buckets: [0.1, 0.5, 1, 2, 5],
});

const activeConnections = new promClient.Gauge({
    name: "active_connections",
    help: "Number of active connections",
});

// Middleware
app.use((req, res, next) => {
    const end = httpRequestDuration.startTimer();
    activeConnections.inc();

res.on("finish", () => {
        end({ method: req.method, route: req.route?.path || "unknown", status: res.statusCode });
        activeConnections.dec();
    });

next();
});

// Metrics endpoint
app.get("/metrics", async (req, res) => {
    res.setHeader("Content-Type", promClient.register.contentType);
    res.end(await promClient.register.metrics());
});

// Health endpoint
app.get("/health", (req, res) => {
    res.json({
        status: "healthy",
        uptime: process.uptime(),
        memory: process.memoryUsage(),
    });
});
```

Node.js: How do you implement a health monitoring dashboard in Node.js?