Preventing pool deletion if pool has healthmonitor

If HM is associated to pool, HM should be deleted prior
to pool deletion.
Trying to delete pool with HM will fail with EntityInUse exception.
This is to preserve common neutron's API concept to delete cascade
resources' subresources only.

Change-Id: I1bfc4d8d8ec7e83b1de11c8fb3e66282bfd06806
Closes-Bug: 1571097
(cherry picked from commit 4effc9b96e)

neutron_lbaas/services/loadbalancer/plugin.py

@@ -893,6 +893,12 @@ class LoadBalancerPluginv2(loadbalancerv2.LoadBalancerPluginBaseV2):
         return self.db.get_pool(context, id).to_api_dict()
 
     def delete_pool(self, context, id):
+        old_lb = self.db.get_pool(context, id)
+        if old_lb.healthmonitor:
+            raise loadbalancerv2.EntityInUse(
+                entity_using=models.HealthMonitorV2.NAME,
+                id=old_lb.healthmonitor.id,
+                entity_in_use=models.PoolV2.NAME)
         self.db.test_and_set_status(context, models.PoolV2, id,
                                     constants.PENDING_DELETE)
         db_pool = self.db.get_pool(context, id)

neutron_lbaas/tests/unit/db/loadbalancer/test_db_loadbalancerv2.py

@@ -2531,6 +2531,17 @@ class LbaasPoolTests(PoolTestBase):
                     self.plugin.db.get_pool_member,
                     ctx, member_id)
 
+    def test_delete_pool_and_hm(self):
+        with self.pool(listener_id=self.listener_id) as pool:
+            pool_id = pool['pool']['id']
+            with self.healthmonitor(pool_id=pool_id):
+                # verify pool deletion is prevented if HM is associated
+                ctx = context.get_admin_context()
+                self.assertRaises(
+                    loadbalancerv2.EntityInUse,
+                    self.plugin.delete_pool,
+                    ctx, pool_id)
+
     def test_cannot_add_multiple_pools_to_listener(self):
         with self.pool(listener_id=self.listener_id):
             data = {'pool': {'name': '',
@@ -3374,6 +3385,7 @@ class LbaasHealthMonitorTests(HealthMonitorTestBase):
                                   'pool_id': self.pool_id}}
         resp, body = self._create_healthmonitor_api(data)
         self.assertEqual(201, resp.status_int)
+        self._delete('healthmonitors', body['healthmonitor']['id'])
 
     def test_create_health_monitor_with_http_method_invalid(self):
         data = {'healthmonitor': {'type': 'HTTP',
@@ -3409,6 +3421,7 @@ class LbaasHealthMonitorTests(HealthMonitorTestBase):
                                   'pool_id': self.pool_id}}
         resp, body = self._create_healthmonitor_api(data)
         self.assertEqual(201, resp.status_int)
+        self._delete('healthmonitors', body['healthmonitor']['id'])
 
     def test_create_health_monitor_with_url_path_invalid(self):
         data = {'healthmonitor': {'type': 'HTTP',