[placement] Demonstrate bug in consumer generation handling

When PUTting allocations to a non-existent consumer, the code
expects the consumer generation to be 'null'. When there is only
one resource provider in the set of allocations sent, this works
well.

Unfortunately when there is more than one resource provider the
loop which calls _new_allocations still uses the 'null' generation
but now the code expects the generation to be 0, because the
consumer now exists.

This patch provides a gabbi test that demonstrates the problem
by creating a shared disk resource provider and associating it
as an aggregate with the existing RP_UUID. A GET
/allocation_candidates is made and a single allocation_request is
returned including both resource providers. A test with a new
consumer is marked as an xfail.

In the next patch the problem will be fixed.

Change-Id: I1238f82dfc46fd9dae126abfd16ce3dd1506e991
Related-Bug: #1778576

nova/tests/functional/api/openstack/placement/gabbits/allocations-1.28.yaml

@@ -166,3 +166,74 @@ tests:
   status: 200
   response_json_paths:
       $.allocations.`len`: 0
+
+# The following tests cover cases where we are putting allocations to
+# multiple resource providers from one consumer uuid, both a brand new
+# consumer and an existing one.
+
+- name: create shared disk
+  POST: /resource_providers
+  data:
+      name: shared_disker
+      uuid: 8aa83304-4b6d-4a23-b954-06d8b36b206a
+
+- name: trait that disk
+  PUT: /resource_providers/8aa83304-4b6d-4a23-b954-06d8b36b206a/traits
+  data:
+      resource_provider_generation: $RESPONSE['$.generation']
+      traits:
+          - MISC_SHARES_VIA_AGGREGATE
+          - STORAGE_DISK_SSD
+
+
+- name: set disk inventory
+  PUT: /resource_providers/8aa83304-4b6d-4a23-b954-06d8b36b206a/inventories
+  data:
+      inventories:
+          DISK_GB:
+              total: 5000
+      resource_provider_generation: $RESPONSE['$.resource_provider_generation']
+
+- name: disk in aggregate
+  PUT: /resource_providers/8aa83304-4b6d-4a23-b954-06d8b36b206a/aggregates
+  data:
+      resource_provider_generation: $RESPONSE['$.resource_provider_generation']
+      aggregates:
+          - 7fade9e1-ab01-4d1b-84db-ac74f740bb42
+
+- name: compute in aggregate
+  PUT: /resource_providers/$ENVIRON['RP_UUID']/aggregates
+  request_headers:
+      # avoid generation in aggregates
+      openstack-api-version: placement 1.10
+  data:
+      - 7fade9e1-ab01-4d1b-84db-ac74f740bb42
+
+- name: get candidates with shared
+  GET: /allocation_candidates?resources=VCPU:1,DISK_GB:200&required=STORAGE_DISK_SSD
+  response_json_paths:
+      $.allocation_requests.`len`: 1
+      $.allocation_requests[0].allocations['$ENVIRON["RP_UUID"]'].resources.VCPU: 1
+      $.allocation_requests[0].allocations['8aa83304-4b6d-4a23-b954-06d8b36b206a'].resources.DISK_GB: 200
+
+# This fails because of bug 1778576
+# https://bugs.launchpad.net/nova/+bug/1778576
+- name: put that allocation to new consumer
+  xfail: True
+  PUT: /allocations/55555555-5555-5555-5555-555555555555
+  data:
+      allocations: $RESPONSE['$.allocation_requests[0].allocations']
+      project_id: $ENVIRON['PROJECT_ID']
+      user_id: $ENVIRON['USER_ID']
+      consumer_generation: null
+  status: 204
+
+- name: put that allocation to existing consumer
+  PUT: /allocations/22222222-2222-2222-2222-222222222222
+  data:
+      allocations: $HISTORY['get candidates with shared'].$RESPONSE['$.allocation_requests[0].allocations']
+      project_id: $ENVIRON['PROJECT_ID']
+      user_id: $ENVIRON['USER_ID']
+      # we just happen to know this is supposed to be 1 here, so shortcutting
+      consumer_generation: 1
+  status: 204