app/templates/haproxy_setup.j2

#!/bin/bash
# HAProxy setup script

sudo apt-get update
sudo apt-get install -y haproxy

# Basic HAProxy config
cat > /etc/haproxy/haproxy.cfg << 'EOF'
global
    log /dev/log local0
    log /dev/log local1 notice
    chroot /var/lib/haproxy
    stats socket /run/haproxy/admin.sock mode 660 level admin expose-fd listeners
    stats timeout 30s
    user haproxy
    group haproxy
    daemon

defaults
    log global
    mode http
    option httplog
    option dontlognull
    timeout connect 5000
    timeout client 50000
    timeout server 50000

frontend http_front
    bind *:80
    default_backend http_back

backend http_back
    balance roundrobin
    server server1 localhost:3000 check
EOF

sudo systemctl enable haproxy
sudo systemctl start haproxy