Lua (httpclient:post): how set timeout for unavailable endpoint

Hello all, I hope you are doing well. If someone has an idea on it, please don’t hesitate :slight_smile:
Thanks a lot and have a great day!

Our context

We are connecting to an external API via https to detect bot activity with lua (

  • The code is executed on the frontend (hook), before calling the backend.
  • If we reach the timeout (detected by httpclient:post), we just let the request go through and we call the backend
  • If bot activity is detected: we respond with a 403

Everything works as expected when the endpoint is available.

Our problem

However, if we have a wrong IP, unresolvable name or unavailability/network problem, the timeout of the function httpclient:post does not work. (we wait a long time before seeing the backend results)
The documentation says that this is the “timeout server”, so we tried a lot of configuration without success, for example:

  • We changed the ‘timeout client’ (and the other values), however this stops the whole frontend execution and does not call the backend (undesirable behavior).
  • We tried ‘tune.lua.*’ variables, but it did not change anything.


  • Maybe we are doing something wrong?
  • Maybe the lua api does not support this?

Code / Configuration

haproxy.cfg (frontend part)

frontend http-in
    http-request lua.my_request_hook
    http-response lua.my_response_hook
    use_backend failure_backend if { var( -m str "blocked" }
    default_backend webservers

lua code

local CONFIG = { ... } 

local res = httpclient:post {
  url     = CONFIG.api_url,
  headers = myHeaders,
  body    = helpers.stringify(myBody),
  timeout = CONFIG.timeout,