[integration tests] Neutron QoS bandwith exceed limit sometimes

[Georgy Dyuldin]

Test result:

https://mirantis.testrail.com/index.php?/tests/view/6109763

Trace:

self = <mos_tests.neutron.python_tests.test_qos.TestTraficBetween3InstancesInOneNet object at 0x7f1a77b97450>
instances = [<Server: server00>, <Server: server01>, <Server: server02>]
os_conn = <mos_tests.environment.os_actions.OpenStackActions object at 0x7f1a77bd1550>
udp = False, clean_port_policy = None

    @pytest.mark.testrail_id('838299', udp=False)
    @pytest.mark.testrail_id('839064', udp=True)
    @pytest.mark.parametrize('udp', [True, False], ids=['udp', 'tcp'])
    def test_traffic_for_one_vm_and_2_another(self, instances, os_conn, udp,
                                              clean_port_policy):
        """Check traffic restriction for one vm between two vms in one net

            Scenario:
                1. Create net01, subnet
                2. Create router01, set gateway and add interface to net01
                3. Boot ubuntu vm1 in net01 on compute-1
                4. Boot ubuntu vm2 in net01 on compute-1
                5. Boot ubuntu vm3 in net01 on compute-2
                6. Start iperf between vm1 and vm2
                7. Look on the traffic with nload on vm port on compute-1
                8. Start iperf between vm1 and vm3
                9. Look on the traffic with nload on vm port on compute-1
                10. Create new policy: neutron qos-policy-create bw-limiter
                11. Create new rule:
                    neutron qos-bandwidth-limit-rule-create rule-id bw-limiter \
                    --max-kbps 3000
                12. Find neutron port for vm1: Neutron port-list | grep <vm1 ip>
                13. Update port with new policy:
                    neutron port-update your-port-id --qos-policy bw-limiter
                14. Check in nload that traffic changed properly
            """

        instance1, instance2, instance3 = instances

        with pytest.raises(AssertionError):
            self.check_iperf_bandwidth(instance1,
                                       instance2,
                                       limit=3000 * 1024,
                                       time=10,
                                       udp=udp)

        with pytest.raises(AssertionError):
            self.check_iperf_bandwidth(instance1,
                                       instance3,
                                       limit=3000 * 1024,
                                       time=10,
                                       udp=udp)

        # Create policy for port
        instance1_ip = os_conn.get_nova_instance_ips(instance1)['fixed']
        port1 = os_conn.get_port_by_fixed_ip(instance1_ip)
        port_policy = os_conn.create_qos_policy('policy_2')
        os_conn.neutron.create_bandwidth_limit_rule(
            port_policy['policy']['id'], {
                'bandwidth_limit_rule': {
                    'max_kbps': 3000,
                }
            })

        os_conn.neutron.update_port(
            port1['id'],
            {'port': {'qos_policy_id': port_policy['policy']['id']}})

        self.check_iperf_bandwidth(instance1,
                                   instance2,
                                   limit=3000 * 1024,
> udp=udp)

mos_tests/neutron/python_tests/test_qos.py:660:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <mos_tests.neutron.python_tests.test_qos.TestTraficBetween3InstancesInOneNet object at 0x7f1a77b97450>
client = <Server: server00>, server = <Server: server01>, limit = 3072000
ip_type = 'fixed', kwargs = {'udp': False}, server_ip = '10.0.0.5'
remote = <mos_tests.environment.ssh.SSHClient object at 0x7f1a77b38fd0> [10.0.0.4:22]
line = ['20160519200758', '10.0.0.4', '45004', '10.0.0.5', '5002', '3', ...]
bandwidth = 3250585, @py_assert3 = 1.05, @py_assert5 = 3225600.0
@py_assert1 = False

    def check_iperf_bandwidth(self,
                              client,
                              server,
                              limit,
                              ip_type='fixed',
                              **kwargs):
        server_ip = self.os_conn.get_nova_instance_ips(server)[ip_type]
        with self.os_conn.ssh_to_instance(
                self.env,
                client,
                username='ubuntu',
                vm_keypair=self.instance_keypair) as remote:
            for line in self.get_iperf_result(remote, server_ip, **kwargs):
                bandwidth = int(line[8])
                if bandwidth < 0.8 * limit:
                    raise Exception(
                        'Bandwidth is too low: {0}, limit is {1}'.format(
                            bandwidth, limit))
> assert bandwidth <= limit * 1.05
E assert 3250585 <= (3072000 * 1.05)

mos_tests/neutron/python_tests/test_qos.py:234: AssertionError