Use sql alchemy to fetch a scalar for the max tunnel id

Bug 1174998

Change-Id: I77203c81c2c910a1a601416efc4567f1320a2eef

quantum/plugins/openvswitch/ovs_db_v2.py

@@ -17,6 +17,7 @@
 # @author: Bob Kukura, Red Hat, Inc.
 
 from sqlalchemy.orm import exc
+from sqlalchemy.sql import func
 
 from quantum.common import exceptions as q_exc
 import quantum.db.api as db
@@ -365,18 +366,9 @@ def get_tunnel_endpoints():
 
 
 def _generate_tunnel_id(session):
-    try:
-        # TODO(rpodolyaka): Query.all() can't raise the NoResultNound exception
-        #                   Fix this later along with other identical cases.
-        tunnels = session.query(ovs_models_v2.TunnelEndpoint).all()
-    except exc.NoResultFound:
-        return 0
-    tunnel_ids = ([tunnel['id'] for tunnel in tunnels])
-    if tunnel_ids:
-        id = max(tunnel_ids)
-    else:
-        id = 0
-    return id + 1
+    max_tunnel_id = session.query(
+        func.max(ovs_models_v2.TunnelEndpoint.id)).scalar() or 0
+    return max_tunnel_id + 1
 
 
 def add_tunnel_endpoint(ip):
@@ -385,8 +377,8 @@ def add_tunnel_endpoint(ip):
         tunnel = (session.query(ovs_models_v2.TunnelEndpoint).
                   filter_by(ip_address=ip).with_lockmode('update').one())
     except exc.NoResultFound:
-        id = _generate_tunnel_id(session)
-        tunnel = ovs_models_v2.TunnelEndpoint(ip, id)
+        tunnel_id = _generate_tunnel_id(session)
+        tunnel = ovs_models_v2.TunnelEndpoint(ip, tunnel_id)
         session.add(tunnel)
         session.flush()
     return tunnel

quantum/tests/unit/openvswitch/test_ovs_db.py

@@ -230,6 +230,14 @@ def test_tunnel_pool(self):
         for tunnel_id in tunnel_ids:
             ovs_db_v2.release_tunnel(self.session, tunnel_id, TUNNEL_RANGES)
 
+    def test_add_tunnel_endpoints(self):
+        tun_1 = ovs_db_v2.add_tunnel_endpoint('192.168.0.1')
+        tun_2 = ovs_db_v2.add_tunnel_endpoint('192.168.0.2')
+        self.assertEquals(1, tun_1.id)
+        self.assertEquals('192.168.0.1', tun_1.ip_address)
+        self.assertEquals(2, tun_2.id)
+        self.assertEquals('192.168.0.2', tun_2.ip_address)
+
     def test_specific_tunnel_inside_pool(self):
         tunnel_id = TUN_MIN + 5
         self.assertFalse(ovs_db_v2.get_tunnel_allocation(tunnel_id).allocated)