Skip rescheduling networks if no DHCP agents available

This eliminates the problem of unscheduled networks in case
of communication failure between agents and servers which
can occur if messaging queue service fails.

Change-Id: Ied4fa301fc3d475bee25c47f3a01c2381ae9a01e
Closes-Bug: #1461714

diff --git a/neutron/db/agentschedulers_db.py b/neutron/db/agentschedulers_db.py
index 61eff9b07cbbe77ec25c9f2a1cc52070aa5f9ef5..b9d9c11dbe59d6c1a213be6ba2cf9a1d72cc5128 100644 (file)
--- a/neutron/db/agentschedulers_db.py
+++ b/neutron/db/agentschedulers_db.py
@@ -271,7 +271,16 @@ class DhcpAgentSchedulerDbMixin(dhcpagentscheduler
         dhcp_notifier = self.agent_notifiers.get(constants.AGENT_TYPE_DHCP)
 
         try:
-            for binding in self._filter_bindings(context, down_bindings):
+            dead_bindings = [b for b in
+                             self._filter_bindings(context, down_bindings)]
+            dead_agents = set([b.dhcp_agent_id for b in dead_bindings])
+            agents = self.get_agents_db(
+                context, {'agent_type': [constants.AGENT_TYPE_DHCP]})
+            if len(agents) == len(dead_agents):
+                LOG.warn(_LW("No DHCP agents available, "
+                             "skipping rescheduling"))
+                return
+            for binding in dead_bindings:
                 LOG.warn(_LW("Removing network %(network)s from agent "
                              "%(agent)s because the agent did not report "
                              "to the server in the last %(dead_time)s "

diff --git a/neutron/tests/unit/scheduler/test_dhcp_agent_scheduler.py b/neutron/tests/unit/scheduler/test_dhcp_agent_scheduler.py
index 5ee1adb16cd4a2338544bd379f826a3d00133624..260a5b01a8d85f0f66abe63be749d75a905179e5 100644 (file)
--- a/neutron/tests/unit/scheduler/test_dhcp_agent_scheduler.py
+++ b/neutron/tests/unit/scheduler/test_dhcp_agent_scheduler.py
@@ -21,6 +21,7 @@ import testscenarios
 from neutron.common import constants
 from neutron import context
 from neutron.db import agentschedulers_db as sched_db
+from neutron.db import common_db_mixin
 from neutron.db import models_v2
 from neutron.extensions import dhcpagentscheduler
 from neutron.scheduler import dhcp_agent_scheduler
@@ -177,7 +178,8 @@ class TestAutoScheduleNetworks(TestDhcpSchedulerBaseTestCase):
 
 
 class TestNetworksFailover(TestDhcpSchedulerBaseTestCase,
-                           sched_db.DhcpAgentSchedulerDbMixin):
+                           sched_db.DhcpAgentSchedulerDbMixin,
+                           common_db_mixin.CommonDbMixin):
     def test_reschedule_network_from_down_agent(self):
         agents = self._create_and_set_agents_down(['host-a', 'host-b'], 1)
         self._test_schedule_bind_network([agents[0]], self.network_id)
@@ -201,7 +203,7 @@ class TestNetworksFailover(TestDhcpSchedulerBaseTestCase,
                 mock.ANY, self.network_id, agents[1].host)
 
     def _test_failed_rescheduling(self, rn_side_effect=None):
-        agents = self._create_and_set_agents_down(['host-a'], 1)
+        agents = self._create_and_set_agents_down(['host-a', 'host-b'], 1)
         self._test_schedule_bind_network([agents[0]], self.network_id)
         with mock.patch.object(self,
                                'remove_network_from_dhcp_agent',
@@ -257,6 +259,14 @@ class TestNetworksFailover(TestDhcpSchedulerBaseTestCase,
             # just make sure that no exception is raised
             self.remove_networks_from_down_agents()
 
+    def test_reschedule_doesnt_occur_if_no_agents(self):
+        agents = self._create_and_set_agents_down(['host-a'], 1)
+        self._test_schedule_bind_network([agents[0]], self.network_id)
+        with mock.patch.object(
+            self, 'remove_network_from_dhcp_agent') as rn:
+            self.remove_networks_from_down_agents()
+            self.assertFalse(rn.called)
+
 
 class DHCPAgentWeightSchedulerTestCase(TestDhcpSchedulerBaseTestCase):
     """Unit test scenarios for WeightScheduler.schedule."""