Hi list,
At my company we are using HAProxy as our main load balancer, and we
have situations where we would like to have TCP load balancing plus some
sort of stickyness (for example, to use SSL-enabled web servers that
need session persistence). The immediate answer would be source IP has,
but that would... well... somehow imbalance backend load.
I have tried to google if it has been already discussed in the list, but
found nothing, but I find weird that such a topic had not raised in the
past.
The RDP-cookie feature got me thinking if that wouldn't be valid as a
new balance algorithm (TCP roundrobin upon the first TCP session and
some kind of stickyness for further connections), as it results
effectively as a balancing method for TCP with backend "session" support.
I'm thinking about something like having a connection table where each
new connection gets inserted upon first session, and somehow assigned an
internal persistent association with a roundrobin-elected backend.
Upon further connections, the proxy would recognize that there was a
"session" in the past and that it would reuse the same backend.
This way we would have the load more balanced (roundrobin) and TCP-level
stickyness. That would be good for balancing PHP applications that store
sessions in local files (as it's the vast majority of that kind of
applications).
I'm not familiar with HAProxy code (yet), and I don't know what would
represent implementing it (I'm willing to if Willy and the "HAProxy
community" welcome the feature), or if it's a good idea in the first
place (after all, RDP-cookie does exactly that, so it seems that it's
useful...), but I think that that new algorithm would be a cleaner
implementation for the RDP-cookie behaviour.
What do you think?
Regards,
L. Alberto Giménez
