blueprint host-aggregates

This is the first of a series of commits that add the host-aggregates capability,
as described on the blueprint page.

This commit, more precisely, introduces changes to the Nova model: model classes
related to aggregates have been added, as well as DB API methods to interact with
the model; a sqlalchemy migration script plus a bunch of tests are also part of
this changeset.

Commits that will follow are going to add:

- Extensions to OSAPI Admin, and related python_novaclient mappings
- Implementation of the XenAPI virt layer
- Integration of OSAPI and virt layer, via the compute_api
- smoketests
- openstack-manuals documentation

These commits will be pushed for review not necessarily in this exact order.

Change-Id: Iceb27609dc53bf4305c02d7cbc436fba4c4a7256

1 files changed, 28 insertions, 0 deletions

diff --git a/nova/compute/aggregate_states.py b/nova/compute/aggregate_states.py
new file mode 100644
index 000000000..bad7720e3
--- /dev/null
+++ b/nova/compute/aggregate_states.py
@@ -0,0 +1,28 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 OpenStack LLC.
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+"""Possible states for host aggregates.
+
+An aggregate may be 'building', in which case the admin has triggered its
+creation, but the underlying hypervisor pool has not actually being created
+yet. An aggregate may be 'active', in which case the underlying hypervisor
+pool is up and running. An aggregate may be in 'error' in all other cases.
+"""
+
+BUILDING = 'building'
+ACTIVE = 'active'
+ERROR = 'error'