Managing HP Serviceguard for Linux, Tenth Edition, September 2012

The interaction of the legal values of dependency_location and
dependency_condition creates the following possibilities:
• Same-node dependency: a package can require that another package be UP on
the same node.
This is the case covered in the section on Simple Dependencies (page 130).
• Different-node dependency: a package can require that another package be UP on
a different node.
• Any-node dependency: a package can require that another package be UP on any
node in the cluster.
• Same-node exclusion: a package can require that another package be DOWN on
the same node. (But this does not prevent that package from being UP on another
node.)
• All-nodes exclusion: a package can require that another package be DOWN on all
nodes in the cluster.
Rules for Exclusionary Dependencies
• All exclusions must be mutual.
That is, if pkg1 requires pkg2 to be DOWN, pkg2 must also require pkg1 to be
DOWN.
By creating an exclusionary relationship between any two packages, you ensure
that only one of them can be running at any time — either on a given node
(same-node exclusion) or throughout the cluster (all-nodes exclusion). A package
can have an exclusionary relationship with any number of other packages, but each
such relationship must be mutual.
• Priority (discussed in detail under “Dragging Rules for Simple Dependencies”
(page 132)) must be set for at least one of the packages in an exclusionary
relationship.
The higher-priority package can force the lower-priority package to halt or (in the
case of a same-node exclusion) move to another eligible node, if any.
• dependency_location must be either same_node or all_nodes, and must
be the same for both packages.
• Both packages must be failover packages whose failover_policy (page 209)
is configured_node.
Rules for different_node and any_node Dependencies
These rules apply to packages whose dependency_condition is UP and whose
dependency_location is different_node or any_node. For same-node
Package Configuration Planning 137