Testing App

Test Three-Tier Stack

In this section of the lab, we will test the following:

Test the complete application flow from HAProxy through Node.js app to Postgres database
Verify connectivity, data persistence, and load balancing functionality.

Verify VM Connectivity

Confirm all three VMs are running and network accessible from your workstation:

Get IP addresses from Prism UI (Compute > VMs) or SSH into each

ping fe-user01-01    # Application VM
ping db-user01-01     # Database VM  
ping haproxy-user01-01 # Load balancer

SSH test from HAProxy VM to app and DB:

# On haproxy-user01-01
ssh ubuntu@fe-user01-01 "curl -I http://localhost:3000"
ssh ubuntu@db-user01-01 "sudo netstat -tlnp | grep 5432"

All VMs must resolve via DHCP hostnames or update /etc/hosts on each VM.

Load Balancing Test

Install wrk tool on your jumphost VM
```
sudo apt install wrk -y
```

Test multiple requests:

wrk -t4 -c100 -d30s http://_HAPROXY_IP/

Check HAProxy stats for even distribution of traffic.

http://_HAPROXY_IP/:8404/stats

Let it run for a few minutes or so and observe.

Performance Validation

Monitor resource usage in Prism UI (Compute > VMs > Analyze):

App VM: CPU < 50%, Memory < 3GB during load tests
DB VM: Disk IOPS low, connections = active users
HAProxy: Minimal CPU/RAM usage

Success criteria: 100% API uptime, data persistence, HAProxy health checks green.

Troubleshooting

Open VSCode > Terminal on your jumphost

Check logs and ensure functionality:

ssh ubuntu@haproxy-user01-01-user01 'sudo journalctl -u haproxy -f' # HAProxy logs
ssh ubuntu@fe-user01-01 'pm2 logs' # App logs
ssh ubuntu@db-user01-01-user01 'sudo tail -f /var/log/postgresql/*.log' # Postgres logs

Common issues:

Issue	Symptoms	Fix
502 Bad Gateway	HAProxy can't reach app	Verify app:3000, firewall, hostname resolution confluence.atlassian
DB Connection Failed	App logs show Postgres errors	Check postgres service, password, todos DB exists github
No HAProxy response	Port 80 blocked	sudo ufw allow 80 or disable firewall