is "stick on hdr()" computed deterministically? (1 reply)

I have a couple HAproxy instances in front of several webservers. The
HAproxies are receiving traffic from an ELB upstream. All HAproxies are
identical.

I want to load balance and make sessions sticky based on the contents of
a request header. In a nutshell, all requests with the same header value
must go to, and stick to, the same backend server.

A configuration I'm thinking of (but I'm not 100% sure it's correct)
might look like this:

backend be_http
mode http
balance hdr(X-Forwarded-For)
hash-type consistent
stick on hdr(X-Forwarded-For)
server s1 x.x.x.x1:8080 check
server s2 x.x.x.x2:8080 check
server s3 x.x.x.x3:8080 check
server s4 x.x.x.x4:8080 check

But here's my question. I have not one, but two HAproxy instances. Are
they going to compute the hash the same way? In other words, for the
same value of that header, is haproxy1 going to send the sessions to the
same backend server as haproxy2?

I need both HAproxy instances to act consistent with each other.
Stickiness based on header value must provide identical results across
all HAproxy instances.

Keep in mind that the two HAproxy instances will split the traffic more
or less equally, so they will see different requests. But all I need is
that hash being computed exactly the same by both HAproxies, in a
deterministic fashion based on A) header values, and B) content of the
backend servers list.

Is that doable?

--
Florin Andrei
http://florin.myip.org/