Add a new configuration parameter rpc_response_max_timeout

A new parameter rpc_response_max_timeout is added and registered into
neutron.conf. (related codes in neutron)

The rpc_response_max_timeout plays a role of the ceiling of timeout
seconds when waiting for the response of a remote rpc server.

During an RPC call, the waiting time starts from the existing parameter
rpc_response_timeout(default 60s) and doubled each time until it reaches
the ceiling which is currently set as 10 times rpc_response_timeout.
It seems to be less flexible since user cannot directly change the
ceiling value unless he/she changes the rpc_response_timeout.

By adding rpc_response_max_timeout, user can now modify it without
changing any other parameters.

In class _BackingOffContextWrapper, _max_timeout and its setters are
useless temporarily because users can now directly change the rpc_max_
timeout in neutron.conf. However, there're not deleted as we should not
prevent the developer to override this parameter.

Co-Authored-By: Allain Legacy<Allain.legacy@windriver.com>

Change-Id: I45d2e5c063d2dd43cb8aec1d46faa3ee8ea4825f
Depends-on: https://review.openstack.org/#/c/626109
Related-Bug: #1805769
Story: 2004456
Task: 28171

neutron_lib/rpc.py

@@ -90,6 +90,10 @@ def _get_default_method_timeouts():
     return collections.defaultdict(_get_default_method_timeout)
 
 
+def _get_rpc_response_max_timeout():
+    return TRANSPORT.conf.rpc_response_max_timeout
+
+
 class _ContextWrapper(object):
     def __init__(self, original_context):
         self._original_context = original_context
@@ -129,7 +133,7 @@ class _BackingOffContextWrapper(_ContextWrapper):
 
     @classmethod
     def get_max_timeout(cls):
-        return cls._max_timeout or _get_default_method_timeout() * 10
+        return cls._max_timeout or _get_rpc_response_max_timeout()
 
     @classmethod
     def set_max_timeout(cls, max_timeout):

neutron_lib/tests/unit/test_rpc.py

@@ -292,6 +292,7 @@ class TimeoutTestCase(base.BaseTestCase):
         self.call_context = mock.Mock()
         self.sleep = mock.patch('time.sleep').start()
         rpc.TRANSPORT.conf.rpc_response_timeout = 10
+        rpc.TRANSPORT.conf.rpc_response_max_timeout = 300
 
     def test_timeout_unaffected_when_explicitly_set(self):
         rpc.TRANSPORT.conf.rpc_response_timeout = 5
@@ -343,19 +344,19 @@ class TimeoutTestCase(base.BaseTestCase):
                     for call in rpc.TRANSPORT._send.call_args_list]
         self.assertEqual([1, 2, 4, 8, 16], timeouts)
 
-    def test_method_timeout_10x_config_ceiling(self):
+    def test_method_timeout_config_ceiling(self):
         rpc.TRANSPORT.conf.rpc_response_timeout = 10
         # 5 doublings should max out at the 10xdefault ceiling
         for i in range(5):
             with testtools.ExpectedException(messaging.MessagingTimeout):
                 self.client.call(self.call_context, 'method_1')
         self.assertEqual(
-            10 * rpc.TRANSPORT.conf.rpc_response_timeout,
+            rpc.TRANSPORT.conf.rpc_response_max_timeout,
             rpc._BackingOffContextWrapper._METHOD_TIMEOUTS['method_1'])
         with testtools.ExpectedException(messaging.MessagingTimeout):
             self.client.call(self.call_context, 'method_1')
         self.assertEqual(
-            10 * rpc.TRANSPORT.conf.rpc_response_timeout,
+            rpc.TRANSPORT.conf.rpc_response_max_timeout,
             rpc._BackingOffContextWrapper._METHOD_TIMEOUTS['method_1'])
 
     def test_timeout_unchanged_on_other_exception(self):
@@ -426,7 +427,8 @@ class TimeoutTestCase(base.BaseTestCase):
     def test_set_max_timeout_overrides_default_timeout(self):
         rpc.TRANSPORT.conf.rpc_response_timeout = 10
         self.assertEqual(
-            10 * 10, rpc._BackingOffContextWrapper.get_max_timeout())
+            rpc.TRANSPORT.conf.rpc_response_max_timeout,
+            rpc._BackingOffContextWrapper.get_max_timeout())
         rpc._BackingOffContextWrapper.set_max_timeout(10)
         self.assertEqual(10, rpc._BackingOffContextWrapper.get_max_timeout())
 

releasenotes/notes/add-a-getter-for-a-newly-added-option-2082877bf7dd136b.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - Maximum rpc timeout is now configurable by ``rpc_response_max_timeout``
+    from Neutron config instead of being calculated as ``10 *
+    rpc_response_timeout`` value.