[lvs-users] Persistent connections

Tracy Reed treed at ultraviolet.org
Fri Jul 2 21:01:19 BST 2010

Hello all,

We are using LVS with the Piranaha GUI that comes with CentOS 5.4. I
have a couple of questions:

We have a few VIPs configured, some of which use persistence. But the
output of --persistent-conn doesn't make any sense to us.

rr.mydomain.com is our very busy load balanced web app. PersistConn
shows 0. But webmail.mydomain.com is our very lightly loaded webmail
cluster. It gets maybe an access every 30 minutes. With a persistence
timeout of 3600 4 and 6 might make some sense. But 0 for rr makes no
sense at all. 0 active connections for dbro and dbrw makes no sense
also. I have a connection to it right now and it still shows zero.

[root at dblvs1 ~]# /sbin/ipvsadm --list --persistent-conn
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port            Weight    PersistConn ActiveConn InActConn 
  -> RemoteAddress:Port
TCP  rr.mydomain.com:htt wlc persistent 7500
  -> rr1.mydomain.com:ht 1         0           0          0         
  -> rr2.mydomain.com:ht 1         0           0          0         
TCP  webmail.mydomain.co wlc persistent 3600
  -> webmail2.mydomain.c 1         4           0          0         
  -> webmail1.mydomain.c 1         6           0          0         
TCP  rr.mydomain.com:htt wlc persistent 7500
  -> rr2.mydomain.com:ht 1         0           0          0         
  -> rr1.mydomain.com:ht 1         0           0          0         
TCP  dbro.mydomain.com:m wlc
  -> db3.mydomain.com:my 1         0           0          0         
TCP  dbrw.mydomain.com:m wlc
  -> db1.mydomain.com:my 1         0           0          0         

Another weird thing is that with wlc (the default, at least when
configured with piranha) we generally only see traffic being sent to
rr1 and very rarely to rr2. Is this normal? I have a hunch "weighted
least connections" means traffic goes to whichever machine has the
fewest connections but when they both have zero it would be nice for
my developer's confidence in lvs if it fell back to round robin
instead of all going to the same machine. We could just use roundrobin
but as long as the persistence and active connection numbers aren't
making sense we wanted to stick with as close to a default config
as possible until we figure that out.

Also note that rr.mydomain.com appears twice because one is http and
the other is https. Are there any problems with running two pools of
servers on the same IPs but on different ports? It seems like it
should work to me but someone here has questioned whether that might
somehow be confusing our connections numbers.


Tracy Reed
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