Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss

CARP master election changed in 11.0 ?

69 views
Skip to first unread message

Robert Blayzor

unread,
Dec 1, 2016, 3:10:48 PM12/1/16
to
Did something change between 10.x and 11.0 with carp MASTER election and advskew?

I have several 10.3 servers where the master is elected based on the member with the LOWEST advskew.

From a pair of 10.3 servers:

vlan: 100 parent interface: lagg0
carp: MASTER vhid 10 advbase 1 advskew 100

vlan: 100 parent interface: lagg0
carp: BACKUP vhid 10 advbase 1 advskew 110


Deploying a new pair of 11.0-RELEASE servers, I see the opposite; seems like the member with the HIGHEST advskew wins now:


carp: BACKUP vhid 20 advbase 1 advskew 0
groups: lagg

carp: MASTER vhid 20 advbase 1 advskew 100
groups: lagg

Preemption doesn’t seem to matter, even with preemption enabled. (which it is).

From OpenBSD, man reads:

advskew
This optional parameter specifies how much to skew the advbase when sending CARP advertisements. By manipulating advskew, the master CARP host can be chosen. The higher the number, the less preferred the host will be when choosing a master. The default is 0. Acceptable values are from 0 to 254.


And this seems true in 10.3 but reversed in 11.0 ?

--
inoc.net!rblayzor
XMPP: rblayzor.AT.inoc.net
PGP Key: 78BEDCE1 @ pgp.mit.edu

_______________________________________________
freebsd...@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/freebsd-stable
To unsubscribe, send any mail to "freebsd-stabl...@freebsd.org"

Robert Blayzor

unread,
Dec 3, 2016, 9:44:06 AM12/3/16
to
Disregard, this problem has been semi-solved. For reasons unknown now it was due to carp send error penalties being applied to one of the servers, which are added to the advskew.

Since a lagg interface is involved:

carp: demoted by 10 to 10 (send error 50 on lagg0)
carp: demoted by 10 to 20 (send error 50 on lagg0)


But what is strange is that the two servers in the VHID have the same exact hardware. Experiencing this send error on one but not the other…

Ultimately the work around was adjusting
net.inet.carp.senderr_demotion_factor -> 10

From it’s default of 240.


Since these errors appear only at startup and not incrementing, it doesn’t really look like a problem.


net.inet.carp.ifdown_demotion_factor: 240
net.inet.carp.senderr_demotion_factor: 10
net.inet.carp.demotion: 20


--
inoc.net!rblayzor
XMPP: rblayzor.AT.inoc.net
PGP Key: 78BEDCE1 @ pgp.mit.edu

0 new messages