|
On Tue, 2007-06-26 at 11:42 -0500, Konstantin Ivanov wrote:
> OK here's a newbie question; How does the Load Balancer knows which
> server is down so it stops forwarding requests to it.
Strictly speaking, it doesn't.
LVS is essentially a routing framework. It makes decisions on where to
send packets according to a policy that you set - this is composed of
the virtual IP address (VIP), real servers assigned to service requests
for the VIP, a forwarding method, a scheduling method and a "weight"
assigned to each realserver.
What you need is another application which helps you control the
framework. The three most commonly used are (in my experience):
ldirectord
keepalived
heartbeat+mon (+fake, if needed)
Both of these are "self contained" applications which both setup and
manage the framework for you at the same time as monitoring the
realservers. If a realserver fails for some reason, they will detect
that in a configurable amount of time and remove the realserver from
service. When it's OK again, they put it back.
Again, strictly speaking, that's not load balancing - it's service
monitoring *but* the outcome of the service monitoring allows you to not
worry about doing things yourself. Think of it as an automated
sysadmin :)
Graeme
|
