dhcp_agent_scheduler is listed as Neutron extension when deploying OVN via the default devstack config [1] but all related tests (Tempest or Neutron tempest plugin) fail because it seems unsupported [2].
Not exposing the extension would avoid blacklisting those tests.
It's not reproduced in gates because the neutron extensions are overridden in tempest.conf [3].
# openstack extension list --network |grep dhcp_agent_scheduler
| DHCP Agent Scheduler | dhcp_agent_scheduler | Schedule networks among dhcp agents
<testcase classname="tempest.api.network.admin.test_dhcp_agent_scheduler.DHCPAgentSchedulersTestJSON" id="a0856713-6549-470c-a656-e97c8df9a14d" name="test_add_remove_network_from_dhcp_agent" time="0.869" timestamp="2020-02-14T22:45:25+0000">
<failure>Traceback (most recent call last):
File "/root/.rally/verification/verifier-450bcf94-0f4e-4e77-ba34-92595a2339df/repo/tempest/api/network/admin/test_dhcp_agent_scheduler.py", line 74, in test_add_remove_network_from_dhcp_agent
self.assertEqual(agent['agent_type'], 'DHCP agent', 'Could not find '
File "/usr/lib/python3.7/site-packages/testtools/testcase.py", line 411, in assertEqual
self.assertThat(observed, matcher, message)
File "/usr/lib/python3.7/site-packages/testtools/testcase.py", line 498, in assertThat
raise mismatch_error
testtools.matchers._impl.MismatchError: None != 'DHCP agent': Could not find DHCP agent in agent list though dhcp_agent_scheduler is enabled.
</failure>
</testcase>
<testcase classname="tempest.api.network.admin.test_dhcp_agent_scheduler.DHCPAgentSchedulersTestJSON" id="5032b1fe-eb42-4a64-8f3b-6e189d8b5c7d" name="test_list_dhcp_agent_hosting_network" time="0.022" timestamp="2020-02-14T22:45:26+0000" />
<testcase classname="tempest.api.network.admin.test_dhcp_agent_scheduler.DHCPAgentSchedulersTestJSON" id="30c48f98-e45d-4ffb-841c-b8aad57c7587" name="test_list_networks_hosted_by_one_dhcp" time="0.017" timestamp="2020-02-14T22:45:26+0000">
<failure>Traceback (most recent call last):
File "/root/.rally/verification/verifier-450bcf94-0f4e-4e77-ba34-92595a2339df/repo/tempest/api/network/admin/test_dhcp_agent_scheduler.py", line 48, in test_list_networks_hosted_by_one_dhcp
self.assertNotEmpty(agents, "no dhcp agent")
File "/root/.rally/verification/verifier-450bcf94-0f4e-4e77-ba34-92595a2339df/repo/tempest/test.py", line 926, in assertNotEmpty
self.assertTrue(items, msg)
File "/usr/lib/python3.7/site-packages/unittest2/case.py", line 702, in assertTrue
raise self.failureException(msg)
AssertionError: [] is not true : no dhcp agent
</failure>
[1] https://github.com/openstack/networking-ovn/blob/master/devstack/local.conf.sample
[2] https://docs.openstack.org/networking-ovn/latest/admin/features.html
[3] https://5edd209f50acf4f4d5fd-bb1c7e0df0c2b154f674f44976092bb9.ssl.cf2.rackcdn.com/707077/1/check/neutron-ovn-tempest-full-multinode-ovs-master/97b04c0/controller/logs/tempest_conf.txt
