(We rarely hear of anyone using this.)
The director machine can be a real-server too. This is convenient when only a small number of machines are available as servers.
To use this feature, add a real-server with IP 127.0.0.1 (or a local IP on your director) to your lvs_xxx.conf file, rerun the configure script, and reinstall the rc.lvs_xxx files.
You will need to setup the service to listen to the VIP on the director. Some services, eg telnet listen on all IP's on the machine and you won't have to do anything special for them. Other services, eg http have to be specifically configured to listen to each IP. You are _not_ connecting to a service on 127.0.0.1 despite what this instruction might look like.
LocalNode operates independantly of NAT,TUN or DR modules.
from the mailing list
Paul Monaghan wrote:
> Okay, perhaps what I am trying to do can't work for what ever reason but > here it is. I've setup ipvs rules as follows: > > TCP 209.226.95.146:8080 wlc > -> 10.0.0.1:8001 Local 1 1 0 > -> 10.0.0.1:8000 Local 1 0 0
(Wensong) For the LocalNode feature, the load balancer just lets the packets pass to the upper layer (up to service daemon) to process the request. So, the port number of the local service must be equal to that of the virtual service, otherwise it won't work. Maybe I should add some code to check whether the port number of local service is equal to that of virtual service, if not, reject it to avoid such an error.
Testing LocalNode
If you want to explore installing localnode by hand, try this. First make sure scheduling is turned on at the director (this command adds round robin scheduling and direct routing)
$ipvsadm -A -t 192.168.1.110:23 -s rr
With an httpd listening on the VIP (192.168.1.110:80) of the director (192.168.1.1) AND with _no_ entries in the ipvsadm table, the director appears as a normal non-LVS node and you can connect to this service at 192.168.1.110:80 from an outside client. If you then add an external real-server to the ipvsadm table in the normal manner with
/sbin/ipvsadm -a -t 192.168.1.110:80 -r 192.168.1.2
then connecting to 192.168.1.110:80 will display the webpage at the real-server 192.168.1.2:80 and not the director. This is easier to see if the pages are different (eg put the real IP of each machine at the top of the webpage).
Now comes the LocalNode part -
You can now add the director back into the ipvsadm table with
/sbin/ipvsadm -a -t 192.168.1.110:80 -r 127.0.0.1
(or replace 127.0.0.1 by another IP on the director)
Note, the port is the same for LocalNode. LocalNode is independant of the LVS mode (VS-NAT/Tun/DR) that you are using for the other IP:ports.
Shift-reloading the webpage at 192.168.1.110:80 will alternately display the wepages at the server 192.168.1.2 and the director at 192.168.1.1 (if the scheduling is unweighted round robin). If you remove the (external) server with
/sbin/ipvsadm -d -t 192.168.1.110:80 -r 192.168.1.2
you will connect to the LVS only at the directors port. The ipvsadm table will then look like
Protocol Local Addr:Port ==>
Remote Addr Weight ActiveConns TotalConns
...
TCP 192.168.1.110:80 ==>
127.0.0.1 2 3 3
From the client, you cannot tell whether you are connecting directly to the 192.168.1.110:80 socket or through the LVS code.