Strange lvs problem with lost http-requests

To: <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Strange lvs problem with lost http-requests
From: "Lanz, Ralf" <Lanz@xxxxxxx>
Date: Tue, 30 May 2006 20:21:11 +0200
Hello everybody,

I am stuck on a problem using lvs, ultramonkey with heartbeat, load
balancing and Apache (either 1.3.x or 2.x). I did a setup with just two
servers, where the load balancer (ldirectord) for www resides on the
same machine as the real servers. The setup that I used is exactly as
described in
changing actually only the IP-addresses for my setup. I'm using standard
debian sarge. The setup basically works, the virtual IP is accessable
and the load is distributed between the two real machines. If any of the
two machines fail, the other takes the ldiretord. 
The problem is, that whenever apache is running on both machines,
performance (slightly) degrades, and every other http-request to the
web-server is lost with timeout (maybe 1 out of four). Deactivating
either web-server returns the cluster to normal perfomance. I have
checked all involved logs, even turned on debugging for heartbeat. No
clarifying messeges or error. The lost packages are lost without any
log-entry. No firewall is activ. In ipvsadm -L the table seems to be as
it should:

dvgw-web1:/var/log/apache2# ipvsadm -L
IP Virtual Server version 1.0.11 (size=4096) Prot LocalAddress:Port
Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  dvgw-web:www rr
  -> dvgw-web1:www                Local   1      0          0
  -> dvgw-web2:www                Route   1      0          3

Does anybody have any idea what could be wrong or how to get an
information on what happens to the lost requests? 

Thanks for any help


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