[Devel] Re: Loadbalancing using Path-HF with NAT-Support

[Andreas Granig]

Juha Heinanen wrote:
> how does passive LB know that active LB is not anymore functional?  do
> you assume a third monitor process that sends SIP requests through
> active LB and if not successful, make passive active or do LBs somehow
> watch each other?

We currently use heartbeat for LB failover, and the passive host routes 
OPTION requests (one per second) through the active one using sipsak and 
a selfmade responder. If the host itself or the uplink is down, 
heartbeat takes over automatically, and if three consecutive OPTION 
requests are lost, hb_takeover is executed on the standby node. LBs also 
have no local harddisk, but use PXE-boot and two NICs in active-backup 
bonding-mode on two seperate switches to minimize sources of failures.

The setup is quite experimental right now, but especially LB failover 
undergoes intensive testing right now, since it's the most critical part 
in the system.

Andy