Hi Ryan,
On Mon, Jun 01, 2009 at 12:22:57PM -0700, Ryan Schlesinger wrote:
> I've got haproxy set up (with 2 frontends) to load balance a php app
> which works great. However, we're using a java uploader applet that
> doesn't appear to handle cookies. It would be simple for me to have the
> uploader use a URL with the server id in it (just like we're already
> doing with the session id) but I don't see any way to get haproxy to
> treat that parameter as the actual server id. Using hashing is not an
> option as changing the number of running application servers is a normal
> occurrence for us. I also can't use the appsession directive as the
> haproxy session id cache isn't shared between the two frontends (both
> running an instance of haproxy). Can this be done with ACLs and I'm
> missing it?
You could very well use ACLs to match your URL parameter in the
frontend and switch to either backend 1 or backend 2 depending
on the value.
Alternatively, you could hash the URL parameter (balance url_param)
but it would not necessarily be easy for your application to generate
an URL param which will hash back to the same server. So I think that
the ACL method is the most appropriate for your case.
Basically you'd do that :
frontend
acl srv1 url_sub SERVERID=1
acl srv2 url_sub SERVERID=2
acl srv1_up nbsrv(bck1) gt 0
acl srv2_up nbsrv(bck2) gt 0
use_backend bck1 if srv1_up srv1
use_backend bck2 if srv2_up srv2
default_backend bck_lb
backend bck_lb
# Perform load-balancing. Servers state is tracked
# from other backends.
balance roundrobin
server srv1 1.1.1.1 track bck1/srv1
server srv2 1.1.1.2 track bck2/srv2
...
backend bck1
balance roundrobin
server srv1 1.1.1.1 check
backend bck2
balance roundrobin
server srv2 1.1.1.2 check
That's just a guideline, but I think you should manage to get
it working based on that.
Regards,
Willy
