This is neutron error

5-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/eventlet/hubs/hub.py", line 187, in switch
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     return self.greenlet.switch()
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/eventlet/greenthread.py", line 194, in main
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     result = function(*args, **kwargs)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/nova/compute/manager.py", line 1530, in _allocate_network_async
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     dhcp_options=dhcp_options)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 364, in allocate_for_instance
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     port_ids=ports_in_requested_order)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 482, in get_instance_nw_info
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     port_ids)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 496, in _get_instance_nw_info
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     port_ids)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 1161, in _build_network_info_model
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     network_IPs)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 1064, in _nw_info_get_subnets
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     subnets = self._get_subnets_from_port(context, port)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/nova/network/neutronv2/api.py", line 1194, in _get_subnets_from_port
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     data = neutronv2.get_client(context).list_subnets(**search_opts)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 111, in with_params
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     ret = self.function(instance, *args, **kwargs)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 367, in list_subnets
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     **_params)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 1397, in list
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     for r in self._pagination(collection, path, **params):
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 1410, in _pagination
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     res = self.get(path, params=params)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 1383, in get
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     headers=headers, params=params)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 1368, in retry_request
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     headers=headers, params=params)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 1311, in do_request
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     self._handle_fault_response(status_code, replybody)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 1281, in _handle_fault_response
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     exception_handler_v20(status_code, des_error_body)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]   File "/usr/lib/python2.7/dist-packages/neutronclient/v2_0/client.py", line 96, in exception_handler_v20
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]     message=msg)
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1] NeutronClientException: 500-{u'NeutronError': {u'message': u'An unknown exception occurred.', u'type': u'NeutronException', u'detail': u''}}
2015-02-11 04:27:47.751 27771 TRACE nova.compute.manager [instance: e79c6fc6-2a48-453f-86d0-e5eb27169eb1]