Add support for usages in the placement API

GET /resources_providers/{uuid}/usages returns a dictionary of resource
usage by resource class.

Change-Id: I3ad0d16594301635966bd9e9352bc3f1f29dab14
Partially-Implements: blueprint generic-resource-pools

nova/api/openstack/placement/handler.py

@@ -29,6 +29,7 @@ import webob
 from nova.api.openstack.placement.handlers import inventory
 from nova.api.openstack.placement.handlers import resource_provider
 from nova.api.openstack.placement.handlers import root
+from nova.api.openstack.placement.handlers import usage
 from nova.api.openstack.placement import util
 from nova import exception
 
@@ -61,6 +62,9 @@ ROUTE_DECLARATIONS = {
         'PUT': inventory.update_inventory,
         'DELETE': inventory.delete_inventory
     },
+    '/resource_providers/{uuid}/usages': {
+        'GET': usage.list_usages
+    },
 }
 
 

nova/api/openstack/placement/handlers/usage.py

@@ -0,0 +1,55 @@
+#    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.
+"""Placement API handlers for usage information."""
+
+from oslo_serialization import jsonutils
+import webob
+
+from nova.api.openstack.placement import util
+from nova import objects
+
+
+def _serialize_usages(resource_provider, usage):
+    usage_dict = {resource.resource_class: resource.usage
+                  for resource in usage}
+    return {'resource_provider_generation': resource_provider.generation,
+            'usages': usage_dict}
+
+
+@webob.dec.wsgify
+@util.check_accept('application/json')
+def list_usages(req):
+    """GET a dictionary of resource provider usage by resource class.
+
+    If the resource provider does not exist return a 404.
+
+    On success return a 200 with an application/json representation of
+    the usage dictionary.
+    """
+    context = req.environ['placement.context']
+    uuid = util.wsgi_path_item(req.environ, 'uuid')
+
+    # Resource provider object needed for two things: If it is
+    # NotFound we'll get a 404 here, which needs to happen because
+    # get_all_by_resource_provider_uuid can return an empty list.
+    # It is also needed for the generation, used in the outgoing
+    # representation.
+    resource_provider = objects.ResourceProvider.get_by_uuid(
+        context, uuid)
+    usage = objects.UsageList.get_all_by_resource_provider_uuid(
+        context, uuid)
+
+    response = req.response
+    response.body = jsonutils.dumps(
+        _serialize_usages(resource_provider, usage))
+    req.response.content_type = 'application/json'
+    return req.response

nova/tests/functional/api/openstack/placement/fixtures.py

@@ -18,6 +18,8 @@ from oslo_utils import uuidutils
 from nova.api.openstack.placement import deploy
 from nova import conf
 from nova import config
+from nova import context
+from nova import objects
 from nova.tests import fixtures
 
 
@@ -66,3 +68,34 @@ class APIFixture(fixture.GabbiFixture):
         self.main_db_fixture.cleanup()
         if self.conf:
             self.conf.reset()
+
+
+class AllocationFixture(APIFixture):
+    """An APIFixture that has some pre-made Allocations."""
+
+    def start_fixture(self):
+        super(AllocationFixture, self).start_fixture()
+        self.context = context.get_admin_context()
+        # Stealing from the super
+        rp_name = os.environ['RP_NAME']
+        rp_uuid = os.environ['RP_UUID']
+        rp = objects.ResourceProvider(
+            self.context, name=rp_name, uuid=rp_uuid)
+        rp.create()
+        inventory = objects.Inventory(
+            self.context, resource_provider=rp,
+            resource_class='DISK_GB', total=2048)
+        inventory.obj_set_defaults()
+        rp.add_inventory(inventory)
+        allocation = objects.Allocation(
+            self.context, resource_provider=rp,
+            resource_class='DISK_GB',
+            consumer_id=uuidutils.generate_uuid(),
+            used=512)
+        allocation.create()
+        allocation = objects.Allocation(
+            self.context, resource_provider=rp,
+            resource_class='DISK_GB',
+            consumer_id=uuidutils.generate_uuid(),
+            used=512)
+        allocation.create()

nova/tests/functional/api/openstack/placement/gabbits/usage.yaml

@@ -0,0 +1,34 @@
+# More interesting tests for usages are in with_allocations
+
+fixtures:
+    - APIFixture
+
+defaults:
+    request_headers:
+        x-auth-token: admin
+
+tests:
+
+- name: fail to get usages for missing provider
+  GET: /resource_providers/fae14fa3-4b43-498c-a33c-4a1d00edb577/usages
+  status: 404
+
+- name: create provider
+  POST: /resource_providers
+  request_headers:
+      content-type: application/json
+  data:
+      name: a name
+  status: 201
+
+- name: check provider exists
+  GET: $LOCATION
+  response_json_paths:
+      name: a name
+
+- name: get empty usages
+  GET: $LAST_URL/usages
+  request_headers:
+      content-type: application/json
+  response_json_paths:
+      usages: {}

nova/tests/functional/api/openstack/placement/gabbits/with-allocations.yaml

@@ -0,0 +1,25 @@
+
+fixtures:
+    - AllocationFixture
+
+defaults:
+    request_headers:
+        x-auth-token: admin
+
+tests:
+
+- name: confirm inventories
+  GET: /resource_providers/$ENVIRON['RP_UUID']/inventories
+  response_json_paths:
+      $.inventories.DISK_GB.total: 2048
+      $.inventories.DISK_GB.reserved: 0
+
+- name: get usages
+  GET: /resource_providers/$ENVIRON['RP_UUID']/usages
+  response_headers:
+      # use a regex here because charset, which is not only not
+      # required but superfluous, is present
+      content-type: /application/json/
+  response_json_paths:
+      $.resource_provider_generation: 1
+      $.usages.DISK_GB: 1024