The Update Method

The RGM calls the Update method of a resource type implementation to apply any changes that were made by the system administrator to the configuration of the active resource. The Update method is only called on nodes (if any) where the resource is currently online.

The changes that have just been made to the resource configuration are guaranteed to be acceptable to the resource type implementation because the RGM runs the Validate method of the resource type before it runs the Update method. The Validate method is called before the resource or resource group properties are changed and the Validate method can veto the proposed changes. The Update method is called after the changes have been applied to give the active (online) resource the opportunity to take notice of the new settings.

As a resource type developer, you need to cautiously decide the properties that you want to be able to update dynamically and mark those with the TUNABLE = ANYTIME setting in the RTR file. Typically, you can specify that you want to be able to dynamically update any property of a resource type implementation that the fault monitor daemon uses, provided that the Update method implementation at least restarts the monitor daemon.

Possible candidates are as follows:

• Thorough_Probe_Interval

• Retry_Count

• Retry_Interval

• Monitor_retry_count

• Monitor_retry_interval

• Probe_timeout

These properties affect the way a fault monitor daemon does health checking of the service, how often it does it, what history interval it uses to keep track of the errors, and what are the restart thresholds set on it by PMF. To implement updates of these properties the utility scds_pmf_restart() is provided in the DSDL.

If you need to be able to dynamically update a resource property, but the modification of that property might affect the running application, you need to implement the appropriate actions so that the updates to that property are correctly applied to any running instances of the application. Currently there is no way to facilitate this via the DSDL. Update is not passed the modified properties on the command line (as is Validate).