Support multiple backends per domain with the help of some lua

haproxy/haproxy.cfg

@@ -115,10 +115,13 @@ cache basic_cache
 	max-age 86400
 
 backend servers
+	balance leastconn
 	# optional (recommended) ssl, requires CA cert installed on proxy and signeed cert on backends, you can also use "ssl verify none" but ssl can then be trivially mitm'd
 	# default-server ssl verify required ca-file ca-certificates.crt sni req.hdr(Host)
 	# use server based on hostname
-	use-server %[req.hdr(host),lower,map(/etc/haproxy/map/backends.map)] if TRUE
+	#use-server %[req.hdr(host),lower,map(/etc/haproxy/map/backends.map)] if TRUE
+	# use multiple servers with lua
+	use-server %[lua.get_server_names] if TRUE
 
 backend bot_check_post_throttle
 	stick-table type ipv6 size 100k expire 60s store http_req_rate(60s)

src/lua/libs/utils.lua

@@ -41,6 +41,14 @@ function _M.split(inputstr, sep)
 	return t
 end
 
+-- check if elem in list
+function _M.contains(list, elem)
+	for _, v in pairs(list) do
+		if v == elem then return true end
+	end
+	return false
+end
+
 -- return true if hash passes difficulty
 function _M.checkdiff(hash, diff)
 	if #hash == 0 then

src/lua/scripts/register-bot-check.lua

@@ -7,3 +7,16 @@ core.register_action("captcha-check", { 'http-req', }, bot_check.check_captcha_s
 core.register_action("pow-check", { 'http-req', }, bot_check.check_pow_status)
 core.register_action("decide-checks-necessary", { 'http-req', }, bot_check.decide_checks_necessary)
 core.register_action("kill-tor-circuit", { 'http-req', }, bot_check.kill_tor_circuit)
+
+local backends_map = Map.new('/etc/haproxy/map/backends.map', Map._str)
+function get_server_names(txn)
+    local key = txn.sf:hdr("Host")
+    local value = backends_map:lookup(key or "")
+    if value ~= nil then
+        return value
+    else
+        return ""
+    end
+end
+
+core.register_fetches("get_server_names", get_server_names)

src/lua/scripts/register-servers.lua

@@ -1,6 +1,7 @@
 package.path = package.path  .. "./?.lua;/etc/haproxy/scripts/?.lua;/etc/haproxy/libs/?.lua"
 
 local pow_difficulty = tonumber(os.getenv("POW_DIFFICULTY") or 18)
+local utils = require("utils")
 
 -- setup initial server backends based on hosts.map
 function setup_servers()
@@ -22,13 +23,15 @@ function setup_servers()
 	tcp:connect("127.0.0.1", 2000); --TODO: configurable port
 	while line do
 		local domain, backend_host = line:match("([^%s]+)%s+([^%s]+)")
-		-- local host_split = utils.split(backend_host, ":")
+		local new_map_value = server_prefix..counter
-		-- local backend_hostname = host_split[1]
+		local existing_map_value = backends_map:lookup(domain)
-		-- local backend_port = host_split[2]
+		if existing_map_value ~= nil then
+			current_backends = utils.split(existing_map_value, ",")
+			if not utils.contains(current_backends, new_map_value) then
+				new_map_value = new_map_value .. "," .. existing_map_value
+			end
+		end
 		core.set_map("/etc/haproxy/map/backends.map", domain, server_prefix..counter)
-		-- local proxy = core.proxies[backend_name].servers[server_prefix..counter]
-		-- proxy:set_addr(backend_hostname, backend_port)
-		-- proxy:set_ready()
 		local server_name = "servers/websrv"..counter
 		--NOTE: if you have a proper CA setup,
 		if verify_backend_ssl ~= nil then