That's really cool. I've been doing it with weighting, but this is much nicer. Am I right in assuming that in this example, when nearly_full is triggered, it will switch entirely to that? how does the balance between the two backends happen in this instance? Should you just repeat the definition of the first backend within the second to go "wide" with the server spread?
On Sun, Feb 22, 2009 at 7:42 AM, Willy Tarreau <[email protected]> wrote: > Hi Karl, > > On Fri, Feb 20, 2009 at 02:23:37PM -0800, Karl Pietri wrote: > > Hello everyone, > > I am using haproxy with ruby on rails backend servers and am trying > to > > setup a system that will have a few mongrels dedicated to priority > traffic > > and spill over to the main pool if those are busy. > > > > i've attached a diagram of what i'm trying to accomplish. > > > > Eseentially i have 2 pools. all the servers in each pool have maxconn 1 > > (because mongrel sucks). a magorit of servers are in pool A and serve my > > normal traffic. I want to dedicate a few servers to pool B so that they > are > > usually unloaded for some priority traffic. For the trafic going to that > > pool i want it to go to the few servers there unless they are all busy > and > > in that case send the traffic to pool A for processing along with the > rest > > of the stuff. > > > > I thought backup would do this but backup servers are only given traffic > if > > all servers in the pool are down. not if all servers are busy. > > For this you could use an ACL relying on "connslots" or "dst_conn". > "connslots" counts the remaining number of connections that can be > accepted, > server queue included. "dst_conn" counts the number of connections on the > frontend. > > Basically, it would look like this : > > frontend app1 > ... > acl nearly_full connslots(back1) -lt 10 > use_backend back2 if nearly_full > default_backend back1 > > backend back1 > ... > server srv1 127.0.0.1:8001 maxconn 1 maxqueue 2 > server srv1 127.0.0.1:8002 maxconn 1 maxqueue 2 > server srv1 127.0.0.1:8003 maxconn 1 maxqueue 2 > server srv1 127.0.0.1:8004 maxconn 1 maxqueue 2 > server srv1 127.0.0.1:8005 maxconn 1 maxqueue 2 > > backend back2 > ... > server srv1 127.0.0.1:8101 maxconn 1 maxqueue 2 > server srv1 127.0.0.1:8102 maxconn 1 maxqueue 2 > server srv1 127.0.0.1:8103 maxconn 1 maxqueue 2 > server srv1 127.0.0.1:8104 maxconn 1 maxqueue 2 > server srv1 127.0.0.1:8105 maxconn 1 maxqueue 2 > > Etc... I think you get the idea. Please check configuration.txt > for more details about ACL usage if needed. > > Regards, > Willy > > >
