Limit maximum requests / second for a specific path on HAProxy

Question

I'm trying to achieve this scenario :

On a specific path only, I receive a steady 9 requests/sec on the frontend. Everything is fine, use the regular Backend. I now receive 11 req/s, I want to reject any requests above 10. But still want to continue replying to a maximum of 10 req/sec.

Everything I have found and tried implementing (like this : https://blog.codecentric.de/en/2014/12/haproxy-http-header-rate-limiting/), are black or white solution, it drops everything once the rate is reached. So it's a protection against DDOS, abuser, but not a real rate limiting solution.

Is there any way to achieve that ?
PS: using HAproxy 1.5.8

Solution

If you want to use rate-limit sessions, is the following feasible for you?

frontend http_in
   bind 0.0.0.0:80
   acl is_path url_beg /path/example/
   use_backend forwarder if is_path

backend forwarder
   server localhost 127.0.0.1:4444 send-proxy

frontend limit_path_backend
   bind 127.0.0.1:4444 accept-proxy
   rate-limit sessions 10
   default_backend webnodes

Comments

[GregL]

Or by using rate-limit sessions <rate> (docs) in the frontend.

[Bastien974]

Sorry, I forgot to add an important requirement, I need to limit just a specific path, not frontend wide. maxconnrate is a global setting and wouldn't work for me.rate-limit sessions does what I want but is frontend-wide.