[lvs-users] Cluster using only one of two available nodes

Ross Michael (LEEDS PCT) michael.ross at nhs.net
Tue Jul 26 09:13:30 BST 2011

Hi all,

I have something of a bit of an odd issue that I have so far been unable to find a solution for, so I am hoping that you can help.

I have a 4 server rig:
2 x directors (heartbeat HA),
2 x apache servers                 ,
Virtual IP                                    

The HA directors are set up and appear to be working perfectly (and failing over correctly).  The Apache servers are also working as expected and will both happily return content when connected to directly by IP.  However, when connecting through the virtual IP, the currently active director will only send requests to one of the servers and seems to completely ignore the other one.

What makes this rather odd is that the director recognises both apache servers, checks them regularly for response and reports correctly if either one goes down.

ipvsadm -Ln
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP rr persistent 600
  ->             Route   1      0          0
  ->             Route   1      0          0

You can see both servers.  Both are responding to the director alive requests:
Both apache logs report: - - [26/Jul/2011:09:02:30 +0100] "GET /alive.html HTTP/1.1" 200 12 "-" "libwww-perl/5.805"

The director is set up like this:-

        real= gate
        real= gate
        fallback= gate
        receive="Still alive"

If I take out 8.121 (the apache server it insists on using), it will not direct traffic to 8.122.  Something else I have noticed is that if no apache server is available, it will not use the fallback either.

Something else I have noticed, but i am not sure it is relevant is that if I do a ipvsadm -Ln -stats, I get:

IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port               Conns   InPkts  OutPkts  InBytes OutBytes
  -> RemoteAddress:Port
TCP                  358     7618        0   527015        0
  ->                    0        0        0        0        0
  ->                    0        0        0        0        0

Notice that all the connections are on the virtual IP and the real IP's are saying zero across the board even though the system appears (on the surface) to be working properly.  I thought that for every connection via the VIP, it would increment 'Conns, InPkts etc' for the real server, though I could be wrong.

Any thoughts would be most appreciated.




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