How to Set Up Monitoring with Grafana and Prometheus

version: '3.8'
services:
  prometheus:
    image: prom/prometheus:latest
    volumes:
      - ./prometheus.yml:/etc/prometheus/prometheus.yml
      - prometheus_data:/prometheus
    command:
      - --config.file=/etc/prometheus/prometheus.yml
      - --storage.tsdb.retention.time=30d
    ports:
      - '9090:9090'

  grafana:
    image: grafana/grafana:latest
    environment:
      - GF_SECURITY_ADMIN_PASSWORD=admin
    volumes:
      - grafana_data:/var/lib/grafana
    ports:
      - '3001:3000'
    depends_on:
      - prometheus

  alertmanager:
    image: prom/alertmanager:latest
    volumes:
      - ./alertmanager.yml:/etc/alertmanager/alertmanager.yml
    ports:
      - '9093:9093'

volumes:
  prometheus_data:
  grafana_data:

global:
  scrape_interval: 15s
  evaluation_interval: 15s

alerting:
  alertmanagers:
    - static_configs:
        - targets: ['alertmanager:9093']

rule_files:
  - alert_rules.yml

scrape_configs:
  - job_name: 'app'
    static_configs:
      - targets: ['host.docker.internal:3000']
    metrics_path: /metrics

  - job_name: 'prometheus'
    static_configs:
      - targets: ['localhost:9090']

import client from 'prom-client';
import express from 'express';

const register = new client.Registry();
client.collectDefaultMetrics({ register });

// Custom counter for HTTP requests
const httpRequestsTotal = new client.Counter({
  name: 'http_requests_total',
  help: 'Total number of HTTP requests',
  labelNames: ['method', 'path', 'status'],
  registers: [register]
});

// Custom histogram for response duration
const httpDurationSeconds = new client.Histogram({
  name: 'http_request_duration_seconds',
  help: 'HTTP request duration in seconds',
  labelNames: ['method', 'path'],
  buckets: [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5],
  registers: [register]
});

const app = express();

// Middleware to record metrics for every request
app.use((req, res, next) => {
  const end = httpDurationSeconds.startTimer({ method: req.method, path: req.path });
  res.on('finish', () => {
    end();
    httpRequestsTotal.inc({ method: req.method, path: req.path, status: res.statusCode });
  });
  next();
});

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