3.3. Resource Trees - Basics / Definitions
The following illustrates the structure of a resource tree, with a corresponding list that defines each area.
<service name="foo" ...>
<fs name="myfs" ...>
<script name="script_child"/>
</fs>
<ip address="10.1.1.2" .../>
</service>
- Resource trees are XML representations of resources, their attributes, parent/child and sibling relationships. The root of a resource tree is almost always a special type of resource called a service. Resource tree, resource group, and service are usually used interchangeably on this wiki. From RGManager's perspective, a resource tree is an atomic unit. All components of a resource tree are started on the same cluster node.
- fs:myfs and ip:10.1.1.2 are siblings
- fs:myfs is the parent of script:script_child
- script:script_child is the child of fs:myfs
3.3.1. Parent / Child Relationships, Dependencies, and Start Ordering
The rules for parent/child relationships in the resource tree are fairly simple:
- Parents are started before children
- Children must all stop (cleanly) before a parent may be stopped
- From these two, you could say that a child resource is dependent on its parent resource
- In order for a resource to be considered in good health, all of its dependent children must also be in good health
