Monitoring Stack: Grafana + Prometheus

Prometheus mengumpulkan metrics, Grafana memvisualisasikannya. Ini adalah monitoring stack paling populer di industri.

Prometheus

Pull-based metrics collector. Prometheus scrape endpoint /metrics dari aplikasi secara berkala.

# prometheus.yml
scrape_configs:
  - job_name: "api-server"
    scrape_interval: 15s
    static_configs:
      - targets: ["api:3000"]

  - job_name: "postgres"
    static_configs:
      - targets: ["postgres-exporter:9187"]

Metric Types

• Counter — Hanya naik: total requests, total errors
• Gauge — Naik/turun: active connections, memory usage
• Histogram — Distribusi: request duration (p50, p95, p99)
• Summary — Mirip histogram, computed client-side

Instrument App

import { Counter, Histogram, register } from "prom-client";

const httpRequests = new Counter({
  name: "http_requests_total",
  help: "Total HTTP requests",
  labelNames: ["method", "path", "status"],
});

const httpDuration = new Histogram({
  name: "http_request_duration_seconds",
  help: "HTTP request duration",
  labelNames: ["method", "path"],
  buckets: [0.01, 0.05, 0.1, 0.5, 1, 5],
});

// Middleware
app.use((req, res, next) => {
  const end = httpDuration.startTimer({ method: req.method, path: req.path });
  res.on("finish", () => {
    httpRequests.inc({ method: req.method, path: req.path, status: res.statusCode });
    end();
  });
  next();
});

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

Grafana Dashboard

Query PromQL di Grafana untuk membuat dashboard:

# Request rate per detik
rate(http_requests_total[5m])

# Error rate
rate(http_requests_total{status=~"5.."}[5m]) / rate(http_requests_total[5m])

# P95 latency
histogram_quantile(0.95, rate(http_request_duration_seconds_bucket[5m]))