test_dhcpv6_64_subnets fails with IpAddressAlreadyAllocated

[Kevin Benton]

Spotted in ocata test run: http://logs.openstack.org/27/456727/1/check/gate-tempest-dsvm-neutron-dvr-ubuntu-xenial/eca5fdc/logs/testr_results.html.gz

Traceback (most recent call last):
  File "tempest/api/network/test_dhcp_ipv6.py", line 249, in test_dhcpv6_64_subnets
    self._clean_network()
  File "tempest/api/network/test_dhcp_ipv6.py", line 81, in _clean_network
    self.subnets_client.delete_subnet(subnet['id'])
  File "tempest/lib/services/network/subnets_client.py", line 52, in delete_subnet
    return self.delete_resource(uri)
  File "tempest/lib/services/network/base.py", line 41, in delete_resource
    resp, body = self.delete(req_uri)
  File "tempest/lib/common/rest_client.py", line 308, in delete
    return self.request('DELETE', url, extra_headers, headers, body)
  File "tempest/lib/common/rest_client.py", line 666, in request
    self._error_checker(resp, resp_body)
  File "tempest/lib/common/rest_client.py", line 787, in _error_checker
    raise exceptions.Conflict(resp_body, resp=resp)
tempest.lib.exceptions.Conflict: An object with that identifier already exists
Details: {u'message': u'IP address 2003::f816:3eff:fe4b:d2d9 already allocated in subnet bc0ff248-312a-46ef-8ec2-8a6ae10dd4a4', u'detail': u'', u'type': u'IpAddressAlreadyAllocated'}

[Miguel Lavalle (minsel)]

Using the following query in Kibana:

message:"IpAddressAlreadyAllocated" AND build_status:FAILURE AND project:"openstack/neutron"

I get 3 hits in master branch over the past 7 days, none in Ocata. The most recent one was 5 days ago. Two of those hits are in none voting job gate-tempest-dsvm-neutron-multinode-full-ubuntu-xenial-nv.

Looking at screen-q-svc in the failure pointed out by the reporter above, we can see that the code in the ML2 plug-in pre-dates the merge of https://review.openstack.org/#/c/454832/ in the ocata branch, that removed the delete_subnet method, including the logging of "Ports to auto-deallocate:..." that we can see here: http://logs.openstack.org/27/456727/1/check/gate-tempest-dsvm-neutron-dvr-ubuntu-xenial/eca5fdc/logs/screen-q-svc.txt.gz#_2017-04-13_19_26_10_392.

I will watch for occurrences of this bug over the next few days. In the meantime, lowering importance to 'High'