Stopping the Monitor

The Monitor_stop method uses pmfadm -q to see if the probe is running, and if so, uses pmfadm -s to stop it. If the probe is already stopped, the method exits successfully anyway, which guarantees the idempotence of the method.

Be certain to use the KILL signal with pmfadm to stop the probe and not a signal that can be masked, such as TERM. Otherwise, the Monitor_stop method can hang indefinitely and eventually time out. The reason is that the PROBE method calls scha_control() when it is necessary to restart or fail over the data service. When scha_control() calls Monitor_stop as part of the process of bringing the data service offline, if Monitor_stop uses a signal that can be masked, Monitor_stop hangs waiting for scha_control() to complete, and scha_control() hangs waiting for Monitor_stop to complete.

# See if the monitor is running, and if so, kill it.
if pmfadm -q $PMF_TAG; then
   pmfadm -s $PMF_TAG KILL
   if [ $? -ne 0 ]; then
         logger -p ${SYSLOG_FACILITY}.err \
            -t [$SYSLOG_TAG] \
            "${ARGV0} Could not stop monitor for resource " \
            $RESOURCE_NAME
           exit 1
   else
         # could successfully stop the monitor. Log a message.
         logger -p ${SYSLOG_FACILITY}.err \
            -t [$SYSLOG_TAG] \
            "${ARGV0} Monitor for resource " $RESOURCE_NAME \
            " successfully stopped"
   fi
fi
exit 0