On Fri, May 25, 2012 at 10:50:25AM +1000, Andrew Beekhof wrote: > On Fri, May 25, 2012 at 10:04 AM, Lars Ellenberg > <lars.ellenb...@linbit.com> wrote: > > On Sun, May 06, 2012 at 09:45:09PM +1000, Andrew Beekhof wrote: > >> On Thu, May 3, 2012 at 5:38 PM, Lars Ellenberg > >> <lars.ellenb...@linbit.com> wrote: > >> > > >> > People sometimes think they have a use case > >> > for influencing which node will be the DC. > >> > >> Agreed :-) > >> > >> > > >> > Sometimes it is latency (certain cli commands work faster > >> > when done on the DC), > >> > >> Config changes can be run against any node, there is no reason to go > >> to the one on the DC. > >> > >> > sometimes they add a "mostly quorum" > >> > node which may be not quite up to the task of being DC. > >> > >> I'm not sure I buy that. Most of the load would comes from the > >> resources themselves. > >> > >> > Prohibiting a node from becoming DC completely would > >> > mean it can not even be cleanly shutdown (with 1.0.x, no MCP), > >> > or act on its own resources for certain no-quorum policies. > >> > > >> > So here is a patch I have been asked to present for discussion, > >> > >> May one ask where it originated? > >> > >> > against Pacemaker 1.0, that introduces a "dc-prio" configuration > >> > parameter, which will add some skew to the election algorithm. > >> > > >> > > >> > Open questions: > >> > * does it make sense at all? > >> > >> Doubtful :-) > >> > >> > > >> > * election algorithm compatibility, stability: > >> > will the election be correct if some nodes have this patch, > >> > and some don't ? > >> > >> Unlikely, but you could easily make it so by placing it after the > >> version check (and bumping said version in the patch) > >> > >> > * How can it be improved so that a node with dc-prio=0 will > >> > "give up" its DC-role as soon as there is at least one other node > >> > with dc-prio > 0? > >> > >> Short of causing an election every time a node joins... I doubt it. > > > > Where would be a suitable place in the code/fsa to do so? > > Just after the call to exit(0) :)
Just what I thought ;-) > I'd do it at the end of do_started() but only if dc-priority* > 0. > That way you only cause an election if someone who is likely to win it starts. > And people that don't enable this feature are unaffected. > > * Not dc-prio, its 2012, there's no need to save the extra 4 chars :-) Thanks, -- : Lars Ellenberg : LINBIT | Your Way to High Availability : DRBD/HA support and consulting http://www.linbit.com DRBD® and LINBIT® are registered trademarks of LINBIT, Austria. _______________________________________________ Pacemaker mailing list: Pacemaker@oss.clusterlabs.org http://oss.clusterlabs.org/mailman/listinfo/pacemaker Project Home: http://www.clusterlabs.org Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf Bugs: http://bugs.clusterlabs.org
