How to Map Domain Names to Backend Server Pools with HAProxy

blog20210202-01.cfg

frontend default
  bind :80

  # ACL for "example.com" and "www.example.com"
  acl ACL_example.com hdr(host) -i example.com www.example.com
  use_backend be_example.com if ACL_example.com

  # ACL for "example.net"
  acl ACL_example.net hdr(host) -i example.net
  use_backend be_example.net if ACL_example.net

blog20210202-02.cfg

use_backend be_example_net if ACL_example.net

blog20210202-03.cfg

frontend fe_main
  bind :80
  # If Host header is api.example.com then use 
  # api.example.com backend
  use_backend %[req.hdr(Host),lower]

blog20210202-04.cfg

backend api.example.com
  balance            roundrobin
  server api1    127.0.0.1:8080 check
  server api2    127.0.0.1:8081 check

blog20210202-05.map

#domainname           backendname
example.com           be_default
example.net           be_default
api.example.com       be_api
api1.example.net      be_api1
api2.example.com      be_api2
# [...]
api10000.example.com  be_api

blog20210202-06.cfg

frontend default
   bind :80
   use_backend %[req.hdr(host),lower,map_dom(/etc/haproxy/maps/hosts.map,be_default)]

blog20210202-07.cfg

use_backend be_example.com if ACL_example.com

blog20210202-08.cfg

frontend www
  bind :80
  use_backend %[path,map_beg(/etc/haproxy/maps/routes.map,be_default)]

blog20210202-09.map

/api    be_api
/login  be_auth

blog20210202-10.cfg

stats socket /var/run/haproxy.sock
  user haproxy group haproxy mode 660 level admin expose-fd listeners

blog20210202-11.bash

$ echo "help" | sudo socat stdio /var/run/haproxy.sock | grep map

blog20210202-12.txt

add map       : add map entry
clear map <id> : clear the content of this map
del map       : delete map entry
get map       : report the keys and values matching a sample for a map
set map       : modify map entry
show map [id] : report available maps or dump a map's contents

blog20210202-13.sh

$ echo "add map /etc/haproxy/maps/hosts.map api.example.com be_api" | socat stdio /var/run/haproxy.sock

blog20210202-14.sh

$ echo "del map /etc/hapee-2.1/hosts.map api.example.com" | socat  stdio /var/run/haproxy.sock

blog20210202-15.cfg

dynamic-update
  update id /etc/hapee-2.1/maps/domains.map url http://10.0.0.1/domains.map delay 300s