Add router precommit events

This adds PRECOMMIT callback events to the basic router DB
operations (create/update/delete). These are leveraged by the
dependent patch for flavor and provider processing.

This also adds a small context manager to the callback manager
to make it simple to reraise the original first exception raised
during the callback processing to avoid littering the exception
unpacking logic around every 'notify' call.

Partially-Implements: bp/multi-l3-backends
Change-Id: I0479f0054f9c22f8021531c54b138179f9688de5

neutron/db/l3_db.py

@@ -216,14 +216,18 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
             # pre-generate id so it will be available when
             # configuring external gw port
             status = router.get('status', n_const.ROUTER_STATUS_ACTIVE)
-            router_db = Router(id=(router.get('id') or
-                                   uuidutils.generate_uuid()),
-                               tenant_id=tenant_id,
+            router.setdefault('id', uuidutils.generate_uuid())
+            router['tenant_id'] = tenant_id
+            router_db = Router(id=router['id'],
+                               tenant_id=router['tenant_id'],
                                name=router['name'],
                                admin_state_up=router['admin_state_up'],
                                status=status,
                                description=router.get('description'))
             context.session.add(router_db)
+            registry.notify(resources.ROUTER, events.PRECOMMIT_CREATE,
+                            self, context=context, router=router,
+                            router_id=router['id'], router_db=router_db)
             return router_db
 
     def create_router(self, context, router):
@@ -245,8 +249,13 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
         """Update the DB object."""
         with context.session.begin(subtransactions=True):
             router_db = self._get_router(context, router_id)
+            old_router = self._make_router_dict(router_db)
             if data:
                 router_db.update(data)
+            registry.notify(resources.ROUTER, events.PRECOMMIT_UPDATE,
+                            self, context=context, router_id=router_id,
+                            router=data, router_db=router_db,
+                            old_router=old_router)
             return router_db
 
     def update_router(self, context, id, router):
@@ -521,6 +530,8 @@ class L3_NAT_dbonly_mixin(l3.RouterPluginBase,
                                           rp.port.id,
                                           l3_port_check=False)
         with context.session.begin(subtransactions=True):
+            registry.notify(resources.ROUTER, events.PRECOMMIT_DELETE,
+                            self, context=context, router_id=id)
             context.session.delete(router)
 
     def get_router(self, context, id, fields=None):

neutron/tests/unit/extensions/test_l3.py

@@ -3030,6 +3030,66 @@ class L3AgentDbTestCaseBase(L3NatTestCaseMixin):
     def test_floatingips_op_agent(self):
         self._test_notify_op_agent(self._test_floatingips_op_agent)
 
+    def test_router_create_precommit_event(self):
+        nset = lambda *a, **k: setattr(k['router_db'], 'name', 'hello')
+        registry.subscribe(nset, resources.ROUTER, events.PRECOMMIT_CREATE)
+        with self.router() as r:
+            self.assertEqual('hello', r['router']['name'])
+
+    def test_router_create_event_exception_preserved(self):
+        # this exception should be propagated out of the callback and
+        # converted into its API equivalent of 404
+        e404 = mock.Mock(side_effect=l3.RouterNotFound(router_id='1'))
+        registry.subscribe(e404, resources.ROUTER, events.PRECOMMIT_CREATE)
+        res = self._create_router(self.fmt, 'tenid')
+        self.assertEqual(exc.HTTPNotFound.code, res.status_int)
+        # make sure nothing committed
+        body = self._list('routers')
+        self.assertFalse(body['routers'])
+
+    def test_router_update_precommit_event(self):
+        nset = lambda *a, **k: setattr(k['router_db'], 'name',
+                                       k['old_router']['name'] + '_ha!')
+        registry.subscribe(nset, resources.ROUTER, events.PRECOMMIT_UPDATE)
+        with self.router(name='original') as r:
+            update = self._update('routers', r['router']['id'],
+                                  {'router': {'name': 'hi'}})
+            # our rude callback should have changed the name to the original
+            # plus some extra
+            self.assertEqual('original_ha!', update['router']['name'])
+
+    def test_router_update_event_exception_preserved(self):
+        # this exception should be propagated out of the callback and
+        # converted into its API equivalent of 404
+        e404 = mock.Mock(side_effect=l3.RouterNotFound(router_id='1'))
+        registry.subscribe(e404, resources.ROUTER, events.PRECOMMIT_UPDATE)
+        with self.router(name='a') as r:
+            self._update('routers', r['router']['id'],
+                         {'router': {'name': 'hi'}},
+                         expected_code=exc.HTTPNotFound.code)
+        # ensure it stopped the commit
+        new = self._show('routers', r['router']['id'])
+        self.assertEqual('a', new['router']['name'])
+
+    def test_router_delete_precommit_event(self):
+        deleted = []
+        auditor = lambda *a, **k: deleted.append(k['router_id'])
+        registry.subscribe(auditor, resources.ROUTER, events.PRECOMMIT_DELETE)
+        with self.router() as r:
+            self._delete('routers', r['router']['id'])
+        self.assertEqual([r['router']['id']], deleted)
+
+    def test_router_delete_event_exception_preserved(self):
+        # this exception should be propagated out of the callback and
+        # converted into its API equivalent of 409
+        e409 = mock.Mock(side_effect=l3.RouterInUse(router_id='1'))
+        registry.subscribe(e409, resources.ROUTER, events.PRECOMMIT_DELETE)
+        with self.router() as r:
+            self._delete('routers', r['router']['id'],
+                         expected_code=exc.HTTPConflict.code)
+        # ensure it stopped the commit
+        self.assertTrue(self._show('routers', r['router']['id']))
+
 
 class L3BaseForIntTests(test_db_base_plugin_v2.NeutronDbPluginV2TestCase):