How the Monitor_stop Method Works

The RGM calls the Monitor_stop method to stop execution of dns_probe when the sample data service is brought offline.

This section describes the major pieces of the Monitor_stop method for the sample application. This section does not describe functionality that is common to all callback methods, such as the parse_args() function. This section also does not describe using the syslog() function. Common functionality is described in Providing Common Functionality to All Methods.

For the complete listing of the Monitor_stop method, see Monitor_stop Method Code Listing.

What the Monitor_stop Method Does

This method uses the PMF (pmfadm) to check whether the probe is running, and if so, to stop it.

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

Monitor_stop Exit Status

The Monitor_stop method logs an error message if it cannot stop the PROBE method. The RGM puts the sample data service into MONITOR_FAILED state on the primary node or zone, which can panic the node.

Monitor_stop should not exit before the probe has been stopped.