Simplify delete_health_monitor() using cascades

Currently delete_health_monitor() emulates behaviour of
cascade deletion: when a HealthMonitor instance is deleted,
all corresponding PoolMonitorAssociations are queried and
deleted one by one. This can be done automatically by means
of SQLAlchemy if we set proper cascade flags on the relationship
between HealthMonitor and PoolMonitorAssociations models.

Fixes bug 1169107.

Change-Id: I674c381192719a56433f67be53a32203c36ebe2b

quantum/db/loadbalancer/loadbalancer_db.py

@@ -127,6 +127,12 @@ class HealthMonitor(model_base.BASEV2, models_v2.HasId, models_v2.HasTenant):
     status = sa.Column(sa.String(16), nullable=False)
     admin_state_up = sa.Column(sa.Boolean(), nullable=False)
 
+    pools = orm.relationship(
+        "PoolMonitorAssociation",
+        backref="healthmonitor",
+        cascade="all"
+    )
+
 
 class PoolMonitorAssociation(model_base.BASEV2):
     """
@@ -139,8 +145,6 @@ class PoolMonitorAssociation(model_base.BASEV2):
     monitor_id = sa.Column(sa.String(36),
                            sa.ForeignKey("healthmonitors.id"),
                            primary_key=True)
-    monitor = orm.relationship("HealthMonitor",
-                               backref="pools_poolmonitorassociations")
 
 
 class LoadBalancerPluginDb(LoadBalancerPluginBase):
@@ -605,7 +609,7 @@ class LoadBalancerPluginDb(LoadBalancerPluginBase):
 
             assoc = PoolMonitorAssociation(pool_id=pool_id,
                                            monitor_id=monitor_id)
-            assoc.monitor = monitor
+            assoc.healthmonitor = monitor
             pool.monitors.append(assoc)
 
         monitors = []
@@ -746,14 +750,6 @@ class LoadBalancerPluginDb(LoadBalancerPluginBase):
 
     def delete_health_monitor(self, context, id):
         with context.session.begin(subtransactions=True):
-            assoc_qry = context.session.query(PoolMonitorAssociation)
-            pool_qry = context.session.query(Pool)
-            for assoc in assoc_qry.filter_by(monitor_id=id).all():
-                try:
-                    pool = pool_qry.filter_by(id=assoc['pool_id']).one()
-                except exc.NoResultFound:
-                    raise loadbalancer.PoolNotFound(pool_id=pool['id'])
-                pool.monitors.remove(assoc)
             monitor_db = self._get_resource(context, HealthMonitor, id)
             context.session.delete(monitor_db)
 

quantum/plugins/services/agent_loadbalancer/plugin.py

@@ -79,8 +79,8 @@ class LoadBalancerCallbacks(object):
                         m.status = constants.ACTIVE
 
                 for hm in pool.monitors:
-                    if hm.monitor.status in ACTIVE_PENDING:
-                        hm.monitor.status = constants.ACTIVE
+                    if hm.healthmonitor.status in ACTIVE_PENDING:
+                        hm.healthmonitor.status = constants.ACTIVE
 
             if (pool.status != constants.ACTIVE
                 or pool.vip.status != constants.ACTIVE):
@@ -104,9 +104,9 @@ class LoadBalancerCallbacks(object):
                 for m in pool.members if m.status == constants.ACTIVE
             ]
             retval['healthmonitors'] = [
-                self.plugin._make_health_monitor_dict(hm.monitor)
+                self.plugin._make_health_monitor_dict(hm.healthmonitor)
                 for hm in pool.monitors
-                if hm.monitor.status == constants.ACTIVE
+                if hm.healthmonitor.status == constants.ACTIVE
             ]
 
             return retval

quantum/tests/unit/db/loadbalancer/test_db_loadbalancer.py

@@ -836,6 +836,42 @@ class TestLoadBalancer(LoadBalancerPluginDbTestCase):
             res = req.get_response(self.ext_api)
             self.assertEqual(res.status_int, 204)
 
+    def test_delete_healthmonitor_cascade_deletion_of_associations(self):
+        with self.health_monitor(type='HTTP', no_delete=True) as monitor:
+            with self.pool() as pool:
+                data = {
+                    'health_monitor': {
+                        'id': monitor['health_monitor']['id'],
+                        'tenant_id': self._tenant_id
+                    }
+                }
+                req = self.new_create_request(
+                    'pools',
+                    data,
+                    fmt=self.fmt,
+                    id=pool['pool']['id'],
+                    subresource='health_monitors')
+                res = req.get_response(self.ext_api)
+                self.assertEqual(res.status_int, 201)
+
+                ctx = context.get_admin_context()
+
+                # check if we actually have corresponding Pool associations
+                qry = ctx.session.query(ldb.PoolMonitorAssociation)
+                qry = qry.filter_by(monitor_id=monitor['health_monitor']['id'])
+                self.assertTrue(qry.all())
+                # delete the HealthMonitor instance
+                req = self.new_delete_request(
+                    'health_monitors',
+                    monitor['health_monitor']['id']
+                )
+                res = req.get_response(self.ext_api)
+                self.assertEqual(res.status_int, 204)
+                # check if all corresponding Pool associations are deleted
+                qry = ctx.session.query(ldb.PoolMonitorAssociation)
+                qry = qry.filter_by(monitor_id=monitor['health_monitor']['id'])
+                self.assertFalse(qry.all())
+
     def test_show_healthmonitor(self):
         with self.health_monitor() as monitor:
             keys = [('type', "TCP"),