Correctly limit provider summaries when nested

When making a GET /allocation_candidates request with the 'limit'
parameter, include all the providers in the same tree as the providers
mentioned in the allocation requests. That is, in a nested situation,
if we limit the allocation requests to 10, we would usually expect
considerably more than 10 providers in provider summaries, to include
any non-contributing providers in the same tree.

Accomplish this by filtering provider summaries on root_provider_uuid
instead of individual provider uuid.

A gabbi test is added which exercises this in a nested situation.

An existing test is updated to reflect the new filtering style. It
does not exercise the nested scenario.

A reno is added indicating the fix.

Change-Id: I136bd7cd89f1bd54f0d1691268545850af234f18
Story: 2005859
Task: 33654

placement/objects/allocation_candidate.py

@@ -188,16 +188,17 @@ class AllocationCandidates(object):
                 alloc_request_objs = alloc_request_objs[:limit]
             # Limit summaries to only those mentioned in the allocation reqs.
             kept_summary_objs = []
-            alloc_req_rp_uuids = set()
-            # Extract resource provider uuids from the resource requests.
+            alloc_req_root_uuids = set()
+            # Extract root resource provider uuids from the resource requests.
             for aro in alloc_request_objs:
                 for arr in aro.resource_requests:
-                    alloc_req_rp_uuids.add(arr.resource_provider.uuid)
+                    alloc_req_root_uuids.add(
+                        arr.resource_provider.root_provider_uuid)
             for summary in summary_objs:
-                rp_uuid = summary.resource_provider.uuid
+                rp_root_uuid = summary.resource_provider.root_provider_uuid
                 # Skip a summary if we are limiting and haven't selected an
                 # allocation request that uses the resource provider.
-                if rp_uuid not in alloc_req_rp_uuids:
+                if rp_root_uuid not in alloc_req_root_uuids:
                     continue
                 kept_summary_objs.append(summary)
             summary_objs = kept_summary_objs

placement/tests/functional/gabbits/allocation-candidates.yaml

@@ -427,6 +427,19 @@ tests:
       $.allocation_requests..allocations["$ENVIRON['PF2_1_UUID']"].resources.SRIOV_NET_VF: 4
       $.allocation_requests..allocations["$ENVIRON['PF2_2_UUID']"].resources.SRIOV_NET_VF: 4
 
+- name: get allocation candidates nested limit
+  desc: confirm provider summaries are complete, fixes story/2005859
+  GET: /allocation_candidates?resources=VCPU:1,SRIOV_NET_VF:4&limit=1
+  status: 200
+  request_headers:
+      openstack-api-version: placement 1.29
+  response_json_paths:
+      $.allocation_requests.`len`: 1
+      $.allocation_requests[0].allocations.`len`: 2
+      # We expect all the providers that share roots with the allocations.
+      # In this case it the compute node, its two numa nodes and its two pfs.
+      $.provider_summaries.`len`: 5
+
 # Make sure that old microversions can return combinations where
 # sharing providers are involved
 - name: get allocation candidates shared and nested old microversion

placement/tests/unit/objects/test_allocation_candidate.py

@@ -18,28 +18,34 @@ from placement.tests.unit.objects import base
 
 class TestAllocationCandidatesNoDB(base.TestCase):
     def test_limit_results(self):
-        # UUIDs don't have to be real UUIDs to test the logic
+        # Results are limited based on their root provider uuid, not uuid.
+        # For a more "real" test of this functionality, one that exercises
+        # nested providers, see the 'get allocation candidates nested limit'
+        # test in the 'allocation-candidates.yaml' gabbit.
         aro_in = [
             mock.Mock(
                 resource_requests=[
-                    mock.Mock(resource_provider=mock.Mock(uuid=uuid))
+                    mock.Mock(resource_provider=mock.Mock(
+                        root_provider_uuid=uuid))
                     for uuid in (1, 0, 4, 8)]),
             mock.Mock(
                 resource_requests=[
-                    mock.Mock(resource_provider=mock.Mock(uuid=uuid))
+                    mock.Mock(resource_provider=mock.Mock(
+                        root_provider_uuid=uuid))
                     for uuid in (4, 8, 5)]),
             mock.Mock(
                 resource_requests=[
-                    mock.Mock(resource_provider=mock.Mock(uuid=uuid))
+                    mock.Mock(resource_provider=mock.Mock(
+                        root_provider_uuid=uuid))
                     for uuid in (1, 7, 6, 4, 8, 5)]),
         ]
-        sum1 = mock.Mock(resource_provider=mock.Mock(uuid=1))
-        sum0 = mock.Mock(resource_provider=mock.Mock(uuid=0))
-        sum4 = mock.Mock(resource_provider=mock.Mock(uuid=4))
-        sum8 = mock.Mock(resource_provider=mock.Mock(uuid=8))
-        sum5 = mock.Mock(resource_provider=mock.Mock(uuid=5))
-        sum7 = mock.Mock(resource_provider=mock.Mock(uuid=7))
-        sum6 = mock.Mock(resource_provider=mock.Mock(uuid=6))
+        sum1 = mock.Mock(resource_provider=mock.Mock(root_provider_uuid=1))
+        sum0 = mock.Mock(resource_provider=mock.Mock(root_provider_uuid=0))
+        sum4 = mock.Mock(resource_provider=mock.Mock(root_provider_uuid=4))
+        sum8 = mock.Mock(resource_provider=mock.Mock(root_provider_uuid=8))
+        sum5 = mock.Mock(resource_provider=mock.Mock(root_provider_uuid=5))
+        sum7 = mock.Mock(resource_provider=mock.Mock(root_provider_uuid=7))
+        sum6 = mock.Mock(resource_provider=mock.Mock(root_provider_uuid=6))
         sum_in = [sum1, sum0, sum4, sum8, sum5, sum7, sum6]
         aro, sum = allocation_candidate.AllocationCandidates._limit_results(
             self.context, aro_in, sum_in, 2)

releasenotes/notes/limit-nested-allocation-candidates-0886e569d15ad951.yaml

@@ -0,0 +1,11 @@
+---
+fixes:
+  - |
+    Limiting nested resource providers with the ``limit=N`` query parameter
+    when calling ``GET /allocation_candidates`` could result in incomplete
+    provider summaries. This is now fixed so that all resource providers that
+    are in the same trees as any provider mentioned in the limited allocation
+    requests are shown in the provider summaries collection. For more
+    information see `story/2005859`_.
+
+    .. _story/2005859: https://storyboard.openstack.org/#!/story/2005859