RFE: Choose VMware datastore in dependence of the provisioned space

[Christian Berendt]

At the moment the _select_datastore method in the VMware driver chooses the in dependence of the free space. The datastore with the most free space will be chosen for a new instance.

On of our customers want to place new instances on the datastore with the less provisioned space and not the one with the most free space.

The amount of provisioned space is not directly provided by the VMware API and has to be calculated by using the capacity, the free space and the uncommitted bytes of the datastore. provisionedSpace = Capacity - freeSpace - uncommitted.

Following changes are necessary to support the selection of a datastore in dependence of the provisioned space:

* The uncommitted property is not requested by the get_datastore method. The get_datastore method hast to request the uncommitted property.

* The Datastore class does not provide a keyword argument for the amount of provisioned space. A provisioned space keyword argument has to be added to the Datastore class.

* The _select_datastore method has to calculate the provisioned space of a datastore.

* A new configuration parameter datastore_allocation_type with 'provisionedSpace' and 'freeSpace' as choices has to be introduced. The default value should be 'freeSpace' to not change the default behaviour of the _select_datastore method.

* When datastore_allocation_type is set to 'provisionedSpace' then the provisionedSpace will be compared instead of the freeSpace and the datastore with the lowest value for provisionedSpace will be chosen.

[int32bit (int32bit)]

Add 'uncommitted' field to the 'Datastore' class

The 'uncommitted' field is in official API, but not in our Datastore
class, we need it to compute the amount of provisioned space:

provisionedSpace = Capacity - freeSpace - uncommitted

So a `uncommitted` keyword argument has to be added to the Datastore
class.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/402632

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/oslo.vmware 2.16.0 release.

[OpenStack Infra (hudson-openstack)]

Change abandoned by Matt Riedemann (<email address hidden>) on branch: master
Review: https://review.opendev.org/402632