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:

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

   ping app-vm-01.local    # Application VM
   ping db-vm-01.local     # Database VM  
   ping haproxy-vm-01.local # Load balancer
   

2. SSH test from HAProxy VM to app and DB:

   # On haproxy-vm-01
   ssh ubuntu@app-vm-01.local "curl -I http://localhost:3000"
   ssh ubuntu@db-vm-01.local "sudo netstat -tlnp | grep 5432"
   

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

Test HAProxy Load Balancer

1. Access the application through HAProxy frontend:

   Command Command ouput

   # From workstation or haproxy-vm-01
   curl -i http://haproxy-vm-01.local/
   curl http://haproxy-vm-01.local/todos
   curl -X POST http://haproxy-vm-01.local/todos \
     -H "Content-Type: application/json" \
     -d '{"title":"Test Todo","completed":false}'
   

   HTTP/1.1 200 OK
   [{"id":1,"title":"Test Todo","completed":false}]
   

Check HAProxy stats: curl http://haproxy-vm-01.local/haproxy?stats (enable in config).​

Verify App-to-Database Connectivity

1. On app-vm-01, confirm Node.js connects to Postgres:

   # Check app logs
   sudo journalctl -u node -f    # or pm2 logs if using process manager
   tail -f /var/log/node-app.log
   
   # Test direct DB connection from app VM
   sudo apt install postgresql-client
   psql postgres://postgres:labpass@db-vm-01.local:5432/todos -c "SELECT 1;"
   

App should show successful DB queries in logs during curl tests.​

Validate Data Persistence

1. Create and verify data flows through all layers:

   # 1. Create todo via HAProxy
   curl -X POST http://haproxy-vm-01.local/todos \
     -H "Content-Type: application/json" \
     -d '{"title":"Lab Demo Todo","completed":false}' \
     -w "\nStatus: %{http_code}\n"
   

2. List todos (should show new item)

   curl http://haproxy-vm-01.local/todos
   

3. Verify in Postgres directly

   ssh ubuntu@db-vm-01.local "sudo -u postgres psql todos -c \"SELECT * FROM todos;\""
   

Database query should match API response JSON.​

Load Balancing Test (Optional Scale)

1. Deploy second app VM (app-vm-02-userXX) via UI or API, add to HAProxy backend:

2. On the HAProxy VM, modify the /etc/haproxy/haproxy.cfg file to include the second front-end app VM.

   /etc/haproxy/haproxy.cfg

   # Edit /etc/haproxy/haproxy.cfg on haproxy-vm-01
   backend app-servers
       balance roundrobin
       server app1 app-vm-01-user01.local:3000 check
       server app2 app-vm-02-user01.local:3000 check
   

3. Reload haproxy with new settings

   sudo systemctl reload haproxy
   

4. Test multiple requests:

   for i in {1..10}; do curl http://haproxy-vm-01.local/todos; done
   

Check HAProxy stats for even distribution of traffic.

Monitoring and Troubleshooting

Open VSCode > Terminal on your jumphost

Check logs and ensure functionality:

ssh ubuntu@haproxy-vm-01-user01 'sudo journalctl -u haproxy -f' # HAProxy logs
ssh ubuntu@app-vm-01-user01 'pm2 logs' # App logs
ssh ubuntu@db-vm-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

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.