[lvs-users] The effect of wlc, lblc, and persistent

[Malcolm Turnbull]

Eric,

LBLC & DH schedulers can only be used in a completely transparent
forwarding LVS i.e. firewall mark matches the packets of ALL routed
traffic and forwards it to a proxy/squid cache.
This is because they need to see the destination IP address (normal
non-transparent LVS traffic all has destination IP of the VIP)

i.e.
iptables -t mangle -A PREROUTING -p tcp --dport 80 -j MARK --set-mark 1
iptables -t mangle -A PREROUTING -p tcp --dport 443 -j MARK --set-mark 1
ip rule add prio 100 fwmark 1 table 100
ip route add local 0/0 dev lo table 100

More of a description on page 16 of our load balancing web filters guide here:
http://uk.loadbalancer.org/pdffiles/Web_Proxy_Deployment_Guide.pdf





On 1 March 2013 16:34, Robinson, Eric <eric.robinson at psmnv.com> wrote:
> Need some help understanding the effect of wlc, lblc, and persistent.
>
> In our environment, the following realserver configuration in ldirectord results in pretty even load balancing.
>
> # Virtual Server for tomcat(site103), Outside to Inside
> virtual=192.168.5.100:3103
>         real=192.168.10.64:3103 masq
>         real=192.168.10.63:3103 masq
>         service=http
>         request="/mobiledoc/jsp/catalog/xml/CheckDBConnection.jsp"
>         receive="success"
>         scheduler=wlc
>         protocol=tcp
>         checktype=3
>         persistent=15
> Here's the output of ipvsadm -Ln
>
>
> TCP 192.168.5.100:3103 wlc persistent 15
> -> 192.168.10.64:3103 Masq 1 24 15
> -> 192.168.10.63:3103 Masq 1 23 22
>
> Whereas the following config results in very uneven load balancing.
>
> # Virtual Server for tomcat(site077), Outside to Inside
> virtual=192.168.5.100:3077
>         real=192.168.10.64:3077 masq
>         real=192.168.10.63:3077 masq
>         service=http
>         request="/mobiledoc/jsp/catalog/xml/CheckDBConnection.jsp"
>         receive="success"
>         scheduler=lblc
>         protocol=tcp
>         checktype=3
>         persistent=360
> Here's the outpuut of ipvsadm -Ln
> TCP 192.168.5.100:3077 lblc persistent 360
> -> 192.168.10.63:3077 Masq 1 16 9
> -> 192.168.10.64:3077 Masq 1 1 0
> Why is the second one so imbalanced? There are probably 20 computers using the second one, so about half of them should be going to each realserver. Once they connect to a realserver, the connection should persist for at least 360 seconds. But that should not result in such a disparity in the number of connections going to each RS should it?
>
> Wait... if the customer is behind NAT, and all of their workstations appear to be the same source IP, I guess it would cause this behavior?
>
> --
> Eric Robinson
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-- 
Regards,

Malcolm Turnbull.

Loadbalancer.org Ltd.
Phone: +44 (0)870 443 8779
http://www.loadbalancer.org/