In this example HTTP requests are proxied directly as HTTP requests to the HTTP web servers. In the case of HTTPS requests, they are handled with the certificates by HAproxy and then proxied to the web servers as HTTP requests.

The certificates for all virtualhosts being proxied are stored as one PEM format file per certificate/key combination in the directory:
The CAs are also stored as one PEM format file per CA in the directory:

Install HAproxy:
apt-get update && apt-get install haproxy

Configure HAproxy for HTTP and HTTPS load-balancing:

Edit the file /etc/haproxy/haproxy.cfg
log /dev/log local0
log /dev/log local1 notice
chroot /var/lib/haproxy
stats socket /run/haproxy/admin.sock mode 660 level admin
stats timeout 30s
user haproxy
group haproxy
# Default SSL material locations
ca-base /etc/ssl/certs
crt-base /etc/ssl/private
# Default ciphers to use on SSL-enabled listening sockets.
# For more information, see ciphers(1SSL). This list is from:
# https://hynek.me/articles/hardening-your-web-servers-ssl-ciphers/
ssl-default-bind-options no-sslv3
tune.ssl.default-dh-param 2048
log global
mode http
option httplog
option dontlognull
timeout connect 5000
timeout client 50000
timeout server 50000
errorfile 400 /etc/haproxy/errors/400.http
errorfile 403 /etc/haproxy/errors/403.http
errorfile 408 /etc/haproxy/errors/408.http
errorfile 500 /etc/haproxy/errors/500.http
errorfile 502 /etc/haproxy/errors/502.http
errorfile 503 /etc/haproxy/errors/503.http
errorfile 504 /etc/haproxy/errors/504.http
# Added to create separate error and access logs
option log-separate-errors
# ------- HTTP Frontend --------------
frontend http_in
bind *:80
mode http
reqadd X-Forwarded-Proto:\ http
default_backend http_out
# ------- HTTPS Frontend --------------
frontend https_glwp-in
bind *:443 ssl crt /etc/ssl/haproxy_certs/
mode http
reqadd X-Forwarded-Proto:\ https
default_backend http_out
listen stats :2000
mode http
stats enable
stats hide-version
stats realm Haproxy\ Statistics
stats uri /stats
stats auth admin:mypasswd
# ------- HTTP Backend --------------
backend http_out
balance roundrobin
stick-table type ip size 200k expire 60m
stick on src
option forwardfor
option httpclose
http-request set-header X-Forwarded-Port %[dst_port]
option httpchk HEAD /
server web1 webserv1.mynet.net:80 check
server web2 webserv2.mynet.net:80 check
server web3 webserv3.mynet.net:80 check
server web4 webserv4.mynet.net:80 check

Preserving the source IP of client in TCP Proxying

In the above examples the protocols that are being load-balanced are application protocols, where you can retain the Source IP by retrieving it from the HTTP/HTTPS header X-Forwarded-For: (obtained by the option: option forwardfor), but if you use HAProxy as a TCP layer load balancer, in order to retain the source IP(client’s IP) see the following article: http://blog.haproxy.com/2012/06/05/preserve-source-ip-address-despite-reverse-proxies/
It’s a tiny bit complex to understand and implement, especially in the backend server. I have not tried it yet, so I can’t guarantee its validity therefore I can’t give any examples. From what I understand, the only changes needed to the TCP proxying directives(not explained here) are the following 2 requirements:
1) HAProxy Backend configuration includes the extra entry: source usesrc clientip
2) The backend server network settings needs to be configured to have the HaProxy host IP address as the default Gateway.

This way the backend server sees the source IP of the client as if the client connected directly to the backend server and the responses from the backend server are returned via the HAProxy Host.
To be continued soon with practical examples …..

Happy load-balancing 🙂