Fix LB failover when in ERROR

Load balancers in ERROR provisioning status could not be failed over.

One possible scenario where LBs go into ERROR is when services are
started before compute nodes are up on a cluster reboot:

- Octavia services are started
- Health Manager does not receive heartbeat and triggers failover
- Failover fails due to lack of availabble compute nodes to spawn
  amphora VMs

Story: 2005078
Task: 29657

Change-Id: Ic4b4516cd6b2a254ea32939668c906486066da42

octavia/api/v2/controllers/load_balancer.py

@@ -106,6 +106,16 @@ class LoadBalancersController(base.BaseController):
             raise exceptions.LBPendingStateError(
                 state=prov_status, id=id)
 
+    def _test_and_set_failover_prov_status(self, session, id):
+        lb_repo = self.repositories.load_balancer
+        if not lb_repo.set_status_for_failover(session, id,
+                                               constants.PENDING_UPDATE):
+            prov_status = lb_repo.get(session, id=id).provisioning_status
+            LOG.info("Invalid state %(state)s of loadbalancer resource %(id)s",
+                     {"state": prov_status, "id": id})
+            raise exceptions.LBPendingStateError(
+                state=prov_status, id=id)
+
     @staticmethod
     def _validate_network_and_fill_or_validate_subnet(load_balancer):
         network = validate.network_exists_optionally_contains_subnet(
@@ -717,7 +727,7 @@ class FailoverController(LoadBalancersController):
         driver = driver_factory.get_driver(db_lb.provider)
 
         with db_api.get_lock_session() as lock_session:
-            self._test_lb_status(lock_session, self.lb_id)
+            self._test_and_set_failover_prov_status(lock_session, self.lb_id)
             LOG.info("Sending failover request for load balancer %s to the "
                      "provider %s", self.lb_id, driver.name)
             driver_utils.call_provider(

octavia/tests/functional/api/v2/test_load_balancer.py

@@ -1955,7 +1955,7 @@ class TestLoadBalancer(base.BaseAPITest):
                                 status=constants.ERROR)
         self.app.put(self._get_full_path(
             self.LB_PATH.format(lb_id=lb_dict.get('id')) + "/failover"),
-            status=409)
+            status=202)
 
     def test_failover_not_authorized(self):
         project_id = uuidutils.generate_uuid()

releasenotes/notes/fix-lb-error-failover-2c17afaa20c0c97f.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fix load balancers that could not be failed over when in ERROR provisioning
+    status.