Hey there, Maybe this is gonna be a very simple answer. In HAProxy 1.5.18 seems that the defaults maxconn have a global influence and not per backend one.
In my case I have global maxconn at 5120001, while defaults at 256. What I'm trying to achieve is to set for all my backends the same maxconn without having the parameter everywhere. Testing it, I basically saturated the 256 connections right away and everything was queued. But that happened globally and not on a per-backend basis. Is that expected? Thanks! Federico