Update Method

The RGM calls the Update method to notify a running resource that its properties have been changed. The RGM invokes Update after an administrative action succeeds in setting properties of a resource or its group. This method is called on nodes where the resource is online.

Update Overview

The Update method doesn't update properties—that is done by the RGM. Rather, it notifies running processes that an update has occurred. The only process in the sample data service affected by a property update is the fault monitor, so it is this process the Update method stops and restarts.

The Update method must verify the fault monitor is running and then kill it using pmfadm. The method obtains the location of the probe program that implements the fault monitor, then restarts it using pmfadm again.

Stopping the Monitor With Update

The Update method uses pmfadm -q to verify that the monitor is running, and if so kills it with pmfadm -s TERM. If the monitor is successfully terminated, a message to that effect is sent to the administrative user. If the monitor cannot be stopped, Update exits with failure status and sends an error message to the administrative user.

if pmfadm -q $RESOURCE_NAME.monitor; then

# Kill the monitor that is running already
pmfadm -s $PMF_TAG TERM
    if [ $? -ne 0 ]; then
       logger -p ${SYSLOG_FACILITY}.err \
              -t [$SYSLOG_TAG] \
                 "${ARGV0} Could not stop the monitor"
       exit 1
    else
    # could successfully stop DNS. Log a message.
       logger -p ${SYSLOG_FACILITY}.err \
              -t [$RESOURCETYPE_NAME,$RESOURCEGROUP_NAME,$RESOURCE_NAME] \
                 "Monitor for HA-DNS successfully stopped"
    fi

Restarting the Monitor

To restart the monitor, the Update method must locate the script that implements the probe program. The probe program resides in the base directory for the data service, which is pointed to by the RT_basedir property. Update retrieves the value of RT_basedir and stores it in the RT_BASEDIR variable, as follows.

RT_BASEDIR=`scha_resource_get -O RT_BASEDIR -R $RESOURCE_NAME -G \
$RESOURCEGROUP_NAME`

Update then uses the value of RT_BASEDIR with pmfadm to restart the dns_probe program. If successful, Update exits with success and sends a message to that effect to the administrative user. If pmfadm cannot launch the probe program, Update exits with failure status and logs an error message.

Update Exit Status

Update method failure causes the resource to be put into an “update failed” state. This state has no effect on RGM management of the resource, but indicates the failure of the update action to administration tools through the syslog facility.