Haproxy lua http-response http-request buffer

Question

Here's my plan,

I'm setting up some error-page in the Haproxy,I want to control the error pages at load-balancer level.

I've got multiple back-end (different domain), I want to give back a different error-page for each back-end (domain).

The error-page's file are located inside of the haproxy in different directory for each domain.

I'm processing the http-response based on the http-request host header, with the host header I can choose which error page to serve.

I was able to achieve such a objective but when I lunch parallel request for each domains the haproxy start to mix up the response between domains.

I share the lua and the haproxy config


global
  debug
  log /dev/log local0 debug
  lua-load /root/error-page.lua

defaults
  log global
  mode http
  retries                 3
  backlog                 10000
  maxconn                 10000
  timeout connect         3s
  timeout client          30s
  timeout server          180s
  timeout tunnel          120s
  timeout http-keep-alive 1s
  timeout http-request    15s
  timeout queue           30s
  timeout tarpit          60s
  option            redispatch
  option            http-server-close
  option            dontlognull
  option            contstats
  option forceclose
  errorfile 404 /root/errors/404.http
  errorfile 500 /root/errors/5xx.http

frontend http
  bind *:80
  acl error status ge 400
  http-response  lua.error-page if error
  http-request lua.error-page

  use_backend web

backend web

   server web-1 10.93.3.41:1500 check

function file_check(file_name)
  local file_found=io.open(file_name, "r")

  if file_found==nil then
  check = "file not found" .. file_name
  else
     check = "file  found" .. file_name
     local error_file2 =  io.open(file_name, "r")
     local file = error_file2:read("a*")
     error_file2:close()
     return file
  end
end


 function http_request_header(txn)
 host = txn.sf:req_fhdr("host")
 end

function http_response_header(txn)


  local error_code = txn.sf:status()
  local domain = "/root/errors/by-domains/" .. host .. "/error-" .. error_code .. ".html"


  if file_check(domain) ~= nil then
  error_page = file_check(domain)
  error_path = domain
  end


if error_page  ~= nil then
    txn:Debug("lua.error-page: rewrite error page: " .. error_path )
    txn.res:set("")
    txn.res:send(error_page)
    txn.done(txn)
 else
   error_path = "back-end"
   txn:Debug("lua.error-page: rewrite error page: " .. error_path )
  end
end

 core.register_action("error-page", { "http-res" }, http_response_header )
core.register_action("error-page", { "http-req" }, http_request_header )

Which version of haproxy do you use? there was some bug fixes in the latest versions which fixes a lot issues. — Aleksandar

Alessio Alessio · Accepted Answer · 2019-07-22T14:09:03

After debugging the issue and reading the LUA docs I've found out that probably the argument "header host" that I'm fetching from the HTTP request using the method "txn.sf:req_fhdr("host")" is a single value string that is shared between HTTP response.

Haproxy lua http-response http-request buffer

1 Answers