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On Wed, 15 Nov 2006, Stefan Schmidt wrote:
Hi there,
i have a problem loadbalancing DNS udp/53 via LVS DR.
Whenever i have a small number of clients, in the example below it is DNS
realtime blackhole lists used by 10 mailservers.
Redundancy is working fine but granularity seems to be an issue and there is
times when i end up with something like this:
#ipvsadm --list --rate --numeric
UDP 1.2.3.4:53 0 1889 0 173253 0
-> 10.1.53.15:53 0 0 0 18 0
-> 10.1.53.9:53 0 1889 0 173235 0
I don't know, but I thought I'd pop up and say something as
I expect the answer isn't well known. This used to work in
the early days.
UDP schedules by packet (or small groups of packets). The
only thing I can think of is that the director sees all your
clients as being the one client. However I notice your
persistence_granularity is one machine, so that shouldn't be
a problem. Does the persistence_granularity actually get to
the director? (I don't know where it goes - do you see it in
the output of ipvsadm, is it in /proc somewhere?). I
wouldn't change the persistence_timeout till you've got it
working. I think the UDP balancing doesn't roll over to the
next realserver for a bit longer than your value (don't
know, 15sec?)
configuration looks like this:
virtual_server 1.2.3.4 53 {
delay_loop 10
lb_algo wrr
lb_kind DR
protocol UDP
! persistence_timeout 1
! persistence_granularity 255.255.255.255
real_server 10.1.53.9 53 {
...
Same picture if i uncomment the persistence statements.
I noticed there apparently are some slewing algorythms
doing things like a slow start whenever i add a realserver
but i never stumbled over any documentation, can you give
me a hint on where to look for this?
It's in the HOWTO as slow start and thundering herd. I
thought it was in the code from the early days, but
apparently it wasn't and I was mistaken. It's been talked
about enough now that I can't remember if it ever went in or
not.
Joe
--
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
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