Managing HP Serviceguard for Linux Ninth Edition, April 2009

function start_command
{ sg_log 5 "start_command"
# log current PEV_MONITORING_INTERVAL value, PEV_ attribute can be changed
# while the package is running
sg_log 0 "PEV_MONITORING_INTERVAL for $SG_PACKAGE_NAME is $PEV_MONITORING_INTERVAL"
return 0
}
function stop_command
{
sg_log 5 "stop_command"
# log current PEV_MONITORING_INTERVAL value, PEV_ attribute can be changed
# while the package is running
sg_log 0 "PEV_MONITORING_INTERVAL for $SG_PACKAGE_NAME is $PEV_MONITORING_INTERVAL"
return 0
}
typeset -i exit_val=0
case ${1} in
start)
start_command $*
exit_val=$?
;;
stop)
stop_command $*
exit_val=$?
;;
validate)
validate_command $*
exit_val=$?
;;
*)
sg_log 0 "Unknown entry point $1"
;;
esac
exit $exit_val
Using Serviceguard Commands in an External Script
You can use Serviceguard commands (such as cmmodpkg) in an external script. These
commands must not interact with the package itself (that is, the package that runs the
external script) but can interact with other packages. But be careful how you code these
interactions.
If a Serviceguard command interacts with another package, be careful to avoid command
loops. For instance, a command loop might occur under the following circumstances.
Suppose a pkg1 script does a cmmodpkg -d of pkg2, and a pkg2 script does a
cmmodpkg -d of pkg1. If both pkg1 and pkg2 start at the same time, the pkg1 script
now tries to cmmodpkg pkg2. But that cmmodpkg command has to wait for pkg2
startup to complete. The pkg2 script tries to cmmodpkg pkg1, but pkg2 has to wait for
pkg1 startup to complete, thereby causing a command loop.
To avoid this situation, it is a good idea to specify a run_script_timeout and
halt_script_timeout for all packages, especially packages that use Serviceguard
commands in their external scripts. If a timeout is not specified and your package has
a command loop as described above, inconsistent results can occur, including a hung
cluster.
140 Planning and Documenting an HA Cluster