Understanding Serviceguard Package Dependencies, April 2009

Dependency behavior

This section describes the rules Serviceguard uses in managing packages with dependencies.

Using the cmrunpkg command

The following rules apply when you run packages that have dependencies using the cmrunpkg

command:

• cmrunpkg will fail if running the packages specified on the command line will cause another

package to halt. This means if you attempt to run a higher priority package using cmrunpkg, and

this will lead to a lower priority package going down, the command will fail. Say you have the

following configuration:

– pkg1 has an all nodes exclusionary dependency on pkg2

– pkg1 has higher priority than pkg2

– pkg1 is currently down and pkg2 is running

The command cmrunpkg pkg1 will fail, because it will cause pkg2 to halt.

• You can use cmrunpkg to run a package configured with dependencies only if all of its

non-exclusionary dependencies (all packages named in a dependency condition attribute with an

“up” dependency) are either running or specified on the cmrunpkg command line. The order in

which you specify these packages on the command line does not matter. For example:

– if pkg1 has a same_node “up” dependency on pkg2, you can start pkg1 using cmrunpkg if

pkg2 is already up; otherwise you must specify it on the cmrunpkg command line:

cmrunpkg pkg1 pkg2

• If a package has an all nodes exclusionary (down) dependency on another package, both

packages cannot run at the same time. This means that you cannot include both packages on the

cmrunpkg command line.

• If a package has a same node exclusionary (down) dependency or a different node (up)

dependency on another package, you need to use cmrunpkg with the -a option in order to include

both packages on the cmrunpkg command line,. Examples:

– if pkg1 has a same_node “down” dependency on pkg2:

o cmrunpkg pkg1 is allowed

o cmrunpkg pkg1 pkg2 is not allowed

o cmrunpkg –a pkg1 pkg2 is allowed

– if pkg1 has a different node dependency on pkg2:

o cmrunpkg pkg1 is allowed if pkg2 is already running on a different node

o cmrunpkg pkg1 pkg2 is not allowed

o cmrunpkg –a pkg1 pkg2 is allowed

NOTE:

You can use the -t option to the cmrunpkg command to preview the effect

on packages of the command before running the actual command.