Using the Optional Init, Fini, and Boot Methods

Three optional methods, Init, Fini, and Boot, enable the RGM to execute initialization and termination code on a resource.

Using the Init Method

The RGM executes the Init method to perform a one-time initialization of the resource when the resource becomes managed as a result of one of the following conditions:

• The resource group in which the resource is located is switched from an unmanaged to a managed state.

• The resource is created in a resource group that is already managed.

Using the Fini Method

The RGM executes the Fini method to clean up after a resource when that resource is no longer managed by the RGM. The Fini method usually undoes any initializations that were performed by the Init method.

The RGM executes Fini on the node where the resource becomes unmanaged when the following situations arise:

• The resource group that contains the resource is switched to an unmanaged state. In this case, the RGM executes the Fini method on all nodes in the node list.

• The resource is deleted from a managed resource group. In this case, the RGM executes the Fini method on all nodes in the node list.

• A node is deleted from the node list of the resource group that contains the resource. In this case, the RGM executes the Fini method on only the deleted node.

A “node list” is either the resource group's Nodelist or the resource type's Installed_nodes list. Whether “node list” refers to the resource group's Nodelist or the resource type's Installed_nodes list depends on the setting of the resource type's Init_nodes property. You can set the Init_nodes property to RG_PRIMARIES or RT_INSTALLED_NODE. For most resource types, Init_nodes is set to RG_PRIMARIES, the default. In this case, both the Init and Fini methods are executed on the nodes that are specified in the resource group's Nodelist.

The type of initialization that the Init method performs defines the type of cleanup that the Fini method that you implement needs to perform, as follows:

• Cleanup of node-specific configuration.

• Cleanup of cluster-wide configuration.

Guidelines for Implementing a Fini Method

The Fini method that you implement needs to determine whether to perform only cleanup of node-specific configuration or cleanup of both node-specific and cluster-wide configuration.

When a resource becomes unmanaged on only a particular node, the Fini method can clean up local, node-specific configuration. However, the Fini method must not clean up global, cluster-wide configuration, because the resource remains managed on other nodes. If the resource becomes unmanaged cluster-wide, the Fini method can perform cleanup of both node-specific and global configuration. Your Fini method code can distinguish these two cases by determining whether the resource group's node list contains the local node on which your Fini method is executing.

If the local node appears in the resource group's node list, the resource is being deleted or is moving to an unmanaged state. The resource is no longer active on any node. In this case, your Fini method needs to clean up any node-specific configuration on the local node as well as cluster-wide configuration.

If the local node does not appear in the resource group's node list, your Fini method can clean up node-specific configuration on the local node. However, your Fini method must not clean up cluster-wide configuration. In this case, the resource remains active on other nodes.

You must also code the Fini method so that it is idempotent. In other words, even if the Fini method has cleaned up a resource during a previous execution, subsequent calls to the Fini method exit successfully.

Using the Boot Method

The RGM executes the Boot method on nodes that join the cluster, that is, that have just been booted or rebooted.

The Boot method normally performs the same initialization as Init. You must code the Boot method so that it is idempotent. In other words, even if the Boot method has initialized the resource during a previous execution, subsequent calls to the Boot method exit successfully.