Example Caddyfile for using as load balancer

Caddyfile

{
	# Enable Debug mode
	debug

	# Disable admin API
	admin off
}

localhost {
	# https://caddyserver.com/docs/caddyfile/directives/push
	push

	# https://caddyserver.com/docs/caddyfile/directives/encode
	encode zstd gzip

	# https://caddyserver.com/docs/caddyfile/directives/metrics
	metrics /metrics

	# https://caddyserver.com/docs/caddyfile/directives/header
	header {
		# Hide "Server: Caddy"
		-Server
		
		# prevent attacks such as Cross Site Scripting (XSS)
		Content-Security-Policy default-src 'self' *.cloud.skynewz.dev
		
		# enable the cross-site scripting (XSS) filter built into modern web browsers
		X-XSS-Protection 1; mode=block

		# ensures the connection cannot be establish through an insecure HTTP connection 
		Strict-Transport-Security max-age=31536000; includeSubDomains; preload

		# clickjacking protection
		X-Frame-Options DENY

		# provides clickjacking protection. Disable iframes
		X-Frame-Options: SAMEORIGIN

		# disable clients from sniffing the media type
		X-Content-Type-Options nosniff

		# keep referrer data off of HTTP connections
		Referrer-Policy no-referrer-when-downgrade
	}

	# https://caddyserver.com/docs/caddyfile/directives/respond
	# Replace backends health checks and provide one for this LB
	respond /health 200
	
	# https://caddyserver.com/docs/caddyfile/directives/tls
	# tls quentin@lemairepro.fr {
	# 	dns gandi {env.GANDI_API_TOKEN}
	
	# 	# Remove this line to enable Let's Encrypt production certificate
	# 	ca https://acme-staging-v02.api.letsencrypt.org/directory
	# }
	
	# https://caddyserver.com/docs/caddyfile/directives/log
	log {
		output stdout
		format console
	}
	
	# https://caddyserver.com/docs/caddyfile/directives/reverse_proxy
	reverse_proxy * {
		# Specify backend here
		to 127.0.0.1:8001
		to 127.0.0.1:8002
		to 127.0.0.1:8003

		lb_policy round_robin
		lb_try_duration 1s
		lb_try_interval 250ms

		health_path     /health # Backend health check path
		# health_port     80 # Default same as backend port
		health_interval 10s
		health_timeout  2s
		health_status   200
	}
}

docker-compose.yaml

version: "3.8"

services:
  whoami1:
    container_name: whoami1
    hostname: whoami1
    image: traefik/whoami
    ports:
      - 8001:80

  whoami2:
    container_name: whoami2
    hostname: whoami2
    image: traefik/whoami
    ports:
      - 8002:80

  whoami3:
    container_name: whoami3
    hostname: whoami3
    image: traefik/whoami
    ports:
      - 8003:80