On Wed, Sep 10, 2014 at 03:00:15PM +1000, Andrew Beekhof wrote: > >>>>> What are the precise semantics of "dampening" (attrd_updater -d)?
> > Basic idea of "attr_updater -d delay" is in fact > > "wait for the dust to settle", > > especially for attribute based constraints, > > as used with the ping RA. > > > > Current behaviour (afai understand it): > > > > If a new update comes in while a previous update is still "pending", > > the timer of the new update is *ignored*, > > the new value is queued instead, and > > the original timer is restarted. > > I think thats what I wrote but longer :) Absolutely :) > > (UNLESS the "new" value is the same as the currently pending value. > > Otherwise values would never reach the cib if the update interval > > is shorter than the dampening interval.) > > > > Value is put into the cib only if the original timer actually expires, > > or attrd "flushes out" all current values for some other reason. > > > > ----- > > > > Problem: > > for "flapping" or otherwise continually changing values, > > new values won't make it into the cib for "a long time". > > Do we have many attributes like that? I've seen it once for ping attributes with a dieing switch. I guess that qualifies as "Not around here.". > > Workaround: > > use a dampening interval shorter than the update interval. > > > > Problem with that workaround: you may still hit the same undesired > > situations you could reach with immediately updating the values, you > > did not wait for "the dust to settle". > > > > > > Proposal: > > > > add a "update deadline" along with the dampening, which would normally > > be sufficiently larger, and count from the original update (this timer > > would not be restarted). > > > > Optionally feed all updates into an aggregate function. > > Default aggregate function may be "latest value". > > > > Once the "update deadline" is reached, > > (submitted values still changing; flapping? ...) > > write out the current "aggregate" value anyways. -- : 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. _______________________________________________ Linux-HA mailing list [email protected] http://lists.linux-ha.org/mailman/listinfo/linux-ha See also: http://linux-ha.org/ReportingProblems
