Possible states for xen resource pools.
A pool may be ‘created’, in which case the admin has triggered its creation, but the underlying hypervisor pool has not actually being set up yet. A pool may be ‘changing’, meaning that the underlying hypervisor pool is being setup. A pool may be ‘active’, in which case the underlying hypervisor pool is up and running. A pool may be ‘dismissed’ when it has no hosts and it has been deleted. A pool may be in ‘error’ in all other cases. A ‘created’ pool becomes ‘changing’ during the first request of adding a host. During a ‘changing’ status no other requests will be accepted; this is to allow the hypervisor layer to instantiate the underlying pool without any potential race condition that may incur in master/slave-based configurations. The pool goes into the ‘active’ state when the underlying pool has been correctly instantiated. All other operations (e.g. add/remove hosts) that succeed will keep the pool in the ‘active’ state. If a number of continuous requests fail, an ‘active’ pool goes into an ‘error’ state. To recover from such a state, admin intervention is required. Currently an error state is irreversible, that is, in order to recover from it a pool must be deleted.
Checks if aggregate is a hypervisor_pool.