Add request timeout handling for Mellanox Neutron Agent

Add request timeout handling for messages sent to eswitch Daemon.
Using configurable number of retries and increasing waiting interval
between retries resend the message.
If request timeout persists, eswitch daemon is not reachable.
In such case, exit the agent process.

Closes-Bug: #1228827

Change-Id: If1290bedafe7a0dd8a61cbe328510075edeb1e5b
(cherry picked from commit 793c763)

etc/neutron/plugins/mlnx/mlnx_conf.ini

@@ -34,12 +34,20 @@
 # vnic_type = mlnx_direct
 
 # (StrOpt) Eswitch daemon end point connection url
-# daemon_endpoint = 'tcp://127.0.0.1:5001'
+# daemon_endpoint = 'tcp://127.0.0.1:60001'
 
 # The number of milliseconds the agent will wait for
 # response on request to daemon
 # request_timeout = 3000
 
+# The number of retries the agent will send request
+# to daemon before giving up
+# retries = 3
+
+# The backoff rate multiplier for waiting period between retries
+# on request to daemon, i.e. value of 2 will double
+# the request timeout each retry
+# backoff_rate = 2
 
 [agent]
 # Agent's polling interval in seconds

neutron/plugins/mlnx/agent/eswitch_neutron_agent.py

@@ -392,6 +392,10 @@ def daemon_loop(self):
                     # If treat devices fails - must resync with plugin
                     sync = self.process_network_ports(port_info)
                     ports = port_info['current']
+            except exceptions.RequestTimeout:
+                LOG.exception(_("Request timeout in agent event loop "
+                                "eSwitchD is not responding - exiting..."))
+                raise SystemExit(1)
             except Exception:
                 LOG.exception(_("Error in agent event loop"))
                 sync = True

neutron/plugins/mlnx/agent/utils.py

@@ -1,5 +1,3 @@
-# vim: tabstop=4 shiftwidth=4 softtabstop=4
-#
 # Copyright 2013 Mellanox Technologies, Ltd
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -19,6 +17,7 @@
 
 from neutron.openstack.common import jsonutils
 from neutron.openstack.common import log as logging
+from neutron.plugins.mlnx.common.comm_utils import RetryDecorator
 from neutron.plugins.mlnx.common import exceptions
 
 LOG = logging.getLogger(__name__)
@@ -42,6 +41,7 @@ def _conn(self):
             self.poller.register(self._conn, zmq.POLLIN)
         return self.__conn
 
+    @RetryDecorator(exceptions.RequestTimeout)
     def send_msg(self, msg):
         self._conn.send(msg)
 
@@ -55,7 +55,7 @@ def send_msg(self, msg):
             self._conn.close()
             self.poller.unregister(self._conn)
             self.__conn = None
-            raise exceptions.MlnxException(_("eSwitchD: Request timeout"))
+            raise exceptions.RequestTimeout()
 
     def parse_response_msg(self, recv_msg):
         msg = jsonutils.loads(recv_msg)
@@ -69,7 +69,7 @@ def parse_response_msg(self, recv_msg):
         else:
             error_msg = _("Unknown operation status %s") % msg['status']
         LOG.error(error_msg)
-        raise exceptions.MlnxException(error_msg)
+        raise exceptions.OperationFailed(err_msg=error_msg)
 
     def get_attached_vnics(self):
         LOG.debug(_("get_attached_vnics"))

neutron/plugins/mlnx/common/comm_utils.py

@@ -0,0 +1,66 @@
+# Copyright 2013 Mellanox Technologies, Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import functools
+import time
+
+from oslo.config import cfg
+
+from neutron.openstack.common import log as logging
+from neutron.plugins.mlnx.common import config  # noqa
+
+LOG = logging.getLogger(__name__)
+
+
+class RetryDecorator(object):
+    """Retry decorator reruns a method 'retries' times if an exception occurs.
+
+    Decorator for retrying a method if exceptionToCheck exception occurs
+    If method raises exception, retries 'retries' times with increasing
+    back off period between calls with 'interval' multiplier
+
+    :param exceptionToCheck: the exception to check
+    :param interval: initial delay between retries in seconds
+    :param retries: number of times to try before giving up
+    :raises: exceptionToCheck
+    """
+    sleep_fn = time.sleep
+
+    def __init__(self, exception_to_check,
+                 interval=cfg.CONF.ESWITCH.request_timeout / 1000,
+                 retries=cfg.CONF.ESWITCH.retries,
+                 backoff_rate=cfg.CONF.ESWITCH.backoff_rate):
+        self.exc = exception_to_check
+        self.interval = interval
+        self.retries = retries
+        self.backoff_rate = backoff_rate
+
+    def __call__(self, original_func):
+        @functools.wraps(original_func)
+        def decorated(*args, **kwargs):
+            sleep_interval = self.interval
+            num_of_iter = self.retries
+            while num_of_iter > 0:
+                try:
+                    return original_func(*args, **kwargs)
+                except self.exc:
+                    LOG.debug(_("Request timeout - call again after "
+                              "%s seconds"), sleep_interval)
+                    RetryDecorator.sleep_fn(sleep_interval)
+                    num_of_iter -= 1
+                    sleep_interval *= self.backoff_rate
+
+            return original_func(*args, **kwargs)
+        return decorated

neutron/plugins/mlnx/common/config.py

@@ -48,6 +48,13 @@
     cfg.IntOpt('request_timeout', default=3000,
                help=_("The number of milliseconds the agent will wait for "
                       "response on request to daemon.")),
+    cfg.IntOpt('retries', default=3,
+               help=_("The number of retries the agent will send request "
+                      "to daemon before giving up")),
+    cfg.IntOpt('backoff_rate', default=2,
+               help=_("backoff rate multiplier for waiting period between "
+                      "retries for request to daemon, i.e. value of 2 will "
+                      " double the request timeout each retry")),
 ]
 
 agent_opts = [

neutron/plugins/mlnx/common/exceptions.py

@@ -20,3 +20,11 @@
 
 class MlnxException(qexc.NeutronException):
     message = _("Mlnx Exception: %(err_msg)s")
+
+
+class RequestTimeout(qexc.NeutronException):
+    message = _("Request Timeout: no response from eSwitchD")
+
+
+class OperationFailed(qexc.NeutronException):
+    message = _("Operation Failed: %(err_msg)s")

neutron/tests/unit/mlnx/test_mlnx_comm_utils.py

@@ -0,0 +1,139 @@
+# Copyright (c) 2013 OpenStack Foundation
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import mock
+from oslo.config import cfg
+
+from neutron.plugins.mlnx.common.comm_utils import RetryDecorator
+from neutron.plugins.mlnx.common import config  # noqa
+from neutron.plugins.mlnx.common import exceptions
+from neutron.tests import base
+
+
+class WrongException(Exception):
+        pass
+
+
+class TestRetryDecorator(base.BaseTestCase):
+    def setUp(self):
+        super(TestRetryDecorator, self).setUp()
+        self.sleep_fn_p = mock.patch.object(RetryDecorator, 'sleep_fn')
+        self.sleep_fn = self.sleep_fn_p.start()
+        self.addCleanup(self.sleep_fn_p.stop)
+
+    def test_no_retry_required(self):
+        self.counter = 0
+
+        @RetryDecorator(exceptions.RequestTimeout, interval=2,
+                        retries=3, backoff_rate=2)
+        def succeeds():
+            self.counter += 1
+            return 'success'
+
+        ret = succeeds()
+        self.assertFalse(self.sleep_fn.called)
+        self.assertEqual(ret, 'success')
+        self.assertEqual(self.counter, 1)
+
+    def test_retry_zero_times(self):
+        self.counter = 0
+        interval = 2
+        backoff_rate = 2
+        retries = 0
+
+        @RetryDecorator(exceptions.RequestTimeout, interval,
+                        retries, backoff_rate)
+        def always_fails():
+            self.counter += 1
+            raise exceptions.RequestTimeout()
+
+        self.assertRaises(exceptions.RequestTimeout, always_fails)
+        self.assertEqual(self.counter, 1)
+        self.assertFalse(self.sleep_fn.called)
+
+    def test_retries_once(self):
+        self.counter = 0
+        interval = 2
+        backoff_rate = 2
+        retries = 3
+
+        @RetryDecorator(exceptions.RequestTimeout, interval,
+                        retries, backoff_rate)
+        def fails_once():
+            self.counter += 1
+            if self.counter < 2:
+                raise exceptions.RequestTimeout()
+            else:
+                return 'success'
+
+        ret = fails_once()
+        self.assertEqual(ret, 'success')
+        self.assertEqual(self.counter, 2)
+        self.assertEqual(self.sleep_fn.call_count, 1)
+        self.sleep_fn.assert_called_with(interval)
+
+    def test_limit_is_reached(self):
+        self.counter = 0
+        retries = 3
+        interval = 2
+        backoff_rate = 4
+
+        @RetryDecorator(exceptions.RequestTimeout, interval,
+                        retries, backoff_rate)
+        def always_fails():
+            self.counter += 1
+            raise exceptions.RequestTimeout()
+
+        self.assertRaises(exceptions.RequestTimeout, always_fails)
+        self.assertEqual(self.counter, retries + 1)
+        self.assertEqual(self.sleep_fn.call_count, retries)
+
+        expected_sleep_fn_arg = []
+        for i in range(retries):
+            expected_sleep_fn_arg.append(interval)
+            interval *= backoff_rate
+
+        self.sleep_fn.assert_has_calls(map(mock.call, expected_sleep_fn_arg))
+
+    def test_limit_is_reached_with_conf(self):
+        self.counter = 0
+
+        @RetryDecorator(exceptions.RequestTimeout)
+        def always_fails():
+            self.counter += 1
+            raise exceptions.RequestTimeout()
+
+        retry = cfg.CONF.ESWITCH.retries
+        interval = cfg.CONF.ESWITCH.request_timeout / 1000
+        delay_rate = cfg.CONF.ESWITCH.backoff_rate
+
+        expected_sleep_fn_arg = []
+        for i in range(retry):
+            expected_sleep_fn_arg.append(interval)
+            interval *= delay_rate
+
+        self.assertRaises(exceptions.RequestTimeout, always_fails)
+        self.assertEqual(self.counter, retry + 1)
+        self.assertEqual(self.sleep_fn.call_count, retry)
+        self.sleep_fn.assert_has_calls(map(mock.call, expected_sleep_fn_arg))
+
+    def test_wrong_exception_no_retry(self):
+
+        @RetryDecorator(exceptions.RequestTimeout)
+        def raise_unexpected_error():
+            raise WrongException("wrong exception")
+
+        self.assertRaises(WrongException, raise_unexpected_error)
+        self.assertFalse(self.sleep_fn.called)