Add util to generate resource request group UUID

Add a new utility function that can be used to generate a stable UUID
for a resource request group.

Related-Bug: #1922237
See-Also: https://review.opendev.org/785236
Change-Id: Ic3718defd74c2165077bb5a942e46474d3582cf5

neutron_lib/placement/utils.py

@@ -111,6 +111,18 @@ def device_resource_provider_uuid(namespace, host, device, separator=':'):
     return six_uuid5(namespace=namespace, name=name)
 
 
+def resource_request_group_uuid(namespace, qos_rules, separator=':'):
+    """Generate a stable UUID for a resource request group.
+
+    :param namespace: A UUID object identifying a port.
+    :param qos_rules: A list of QoS rules contributing to the group.
+    :param separator: A string used in assembling a name for uuid5(). Optional.
+    :returns: A unique and stable UUID identifying a resource request group.
+    """
+    name = separator.join([rule.id for rule in qos_rules])
+    return six_uuid5(namespace=namespace, name=name)
+
+
 def _parse_rp_rate(rate_str):
     """Parse the config string value to an non-negative integer.
 

neutron_lib/tests/unit/placement/test_utils.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+from unittest import mock
 import uuid
 
 from neutron_lib.placement import utils as place_utils
@@ -73,6 +74,18 @@ class TestPlacementUtils(base.BaseTestCase):
         except Exception:
             self.fail('could not generate device resource provider uuid')
 
+    def test_resource_request_group_uuid(self):
+        try:
+            # assertNotRaises
+            place_utils.resource_request_group_uuid(
+                namespace=self._uuid_ns,
+                qos_rules=[
+                    mock.MagicMock(id='fake_id_0'),
+                    mock.MagicMock(id='fake_id_1')
+                ])
+        except Exception:
+            self.fail('could not generate resource request group uuid')
+
     def test_agent_resource_provider_uuid_stable(self):
         uuid_a = place_utils.agent_resource_provider_uuid(
             namespace=self._uuid_ns,
@@ -93,6 +106,23 @@ class TestPlacementUtils(base.BaseTestCase):
             device='some-device')
         self.assertEqual(uuid_a, uuid_b)
 
+    def test_resource_request_group_uuid_stable(self):
+        uuid_a = place_utils.resource_request_group_uuid(
+            namespace=self._uuid_ns,
+            qos_rules=[
+                mock.MagicMock(id='fake_id_0'),
+                mock.MagicMock(id='fake_id_1')
+            ]
+        )
+        uuid_b = place_utils.resource_request_group_uuid(
+            namespace=self._uuid_ns,
+            qos_rules=[
+                mock.MagicMock(id='fake_id_0'),
+                mock.MagicMock(id='fake_id_1')
+            ]
+        )
+        self.assertEqual(uuid_a, uuid_b)
+
     def test_parse_rp_bandwidths(self):
         self.assertEqual(
             {},