Managing Serviceguard 14th Edition, June 2007

Planning and Documenting an HA Cluster
Package Configuration Planning
Chapter 4174
successor of a package depends on that package; in our example,
pkg1 is a successor of pkg2; conversely pkg2 can be referred to as a
predecessor of pkg1.)
Dragging Rules The priority parameter gives you a way to influence
the startup, failover, and failback behavior of a set of failover packages
that have a configured_node failover_policy, when one or more of
those packages depend on another or others.
The broad rule is that a higher-priority package can drag a
lower-priority package, forcing it to start on, or move to, a node that suits
the higher-priority package.
NOTE This applies only when the packages are automatically started (package
switching enabled); cmrunpkg will never force a package to halt.
Keep in mind that you do not have to set priority, even when one or
more packages depend on another. The default value, no_priority, may
often result in the behavior you want. For example, if pkg1 depends on
pkg2, and priority is set to no_priority for both packages, and other
parameters such as node_name and auto_run are set as recommended in
this section, then pkg1 will normally follow pkg2 to wherever both can
run, and this is the common-sense (and may be the most desirable)
outcome.
The following examples express the rules as they apply to two failover
packages whose failover_policy (see page 285) is configured_node.
Assume pkg1 depends on pkg2, that node1, node2 and node3 are all
specified (in some order) under node_name (see page 282) in the
configuration file for each package, and that failback_policy (see
page 286) is set to automatic for each package.
NOTE Keep the following in mind when reading the examples that follow, and
when actually configuring priorities:
1. auto_run (see page 283) should be set to yes for all the packages
involved; the examples assume that it is.
2. Priorities express a ranking order, so a lower number means a higher
priority (10 is a higher priority than 30, for example).