[ClusterLabs] Coming in Pacemaker 2.0.3: You can (mostly) forget cluster-recheck-interval exists

[Ken Gaillot]

Hi all,

Currently, if you configure a failure-timeout, a reconnect_interval for
an ocf:pacemaker:remote resource, or a rule with a date_expression,
Pacemaker doesn't guarantee checking them more often than the cluster-
recheck-interval (which defaults to 15 minutes).

Often, users either forget to change cluster-recheck-interval, in which
case the action may occur well after intended, or set cluster-recheck-
interval very low, which is inefficient.

With the upcoming Pacemaker 2.0.3, Pacemaker will dynamically compute
the recheck interval based on the configuration. If there's a failure
that will expire 9 minutes from now, Pacemaker will recheck in 9
minutes.

The lone exception is for date expressions using the cron-like
"date_spec" format, due to the difficulty of determining the next
recheck time in that case -- cluster-recheck-interval is still your
friend if you use date_spec.

Pacemaker will continue to check at least as often as cluster-recheck-
interval, both to evaluate date_spec entries and as a fail-safe in case
of certain types of scheduler bugs.
-- 
Ken Gaillot <kgaillot at redhat.com>