Add a new aioeventlet executor

The new executor supports trollius coroutines, explicit asynchronous
programming, in addition to eventlet greenthreads, implicit asynchronous
programming.

The new AsyncioEventletExecutor class is based on the EventletExecutor
class and so it is compatible with it. The aioeventlet executor can be
used to replace the eventlet executor, but it requires an aioeventlet
event loop running in the thread running the executor (usually the main
thread). See AsyncioEventletExecutor docstring for an example how to
setup such event loop.

The aioeventlet module implements the asyncio API (PEP 3156) on top of
eventlet, see aioeventlet documentation:
http://aioeventlet.readthedocs.org/

The change adds an unit test with an endpoint implemented as a trollius
coroutine.

The executor is not supported on Python 3 yet because of eventlet issues
with monkey patching.

Implements: blueprint greenio-executor
Change-Id: I7a78ed998719a703077232726f66d882463b1297

5 files changed, 181 insertions, 16 deletions

diff --git a/oslo_messaging/_executors/impl_aioeventlet.py b/oslo_messaging/_executors/impl_aioeventlet.py
new file mode 100644
index 0000000..d0fc4aa
--- /dev/null
+++ b/oslo_messaging/_executors/impl_aioeventlet.py
@@ -0,0 +1,75 @@
+# Copyright 2014 eNovance.
+#
+#    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 aioeventlet
+import trollius
+
+from oslo_messaging._executors import impl_eventlet
+
+
+class AsyncioEventletExecutor(impl_eventlet.EventletExecutor):
+
+    """A message executor which integrates with eventlet and trollius.
+
+    The executor is based on eventlet executor and so is compatible with it.
+    The executor supports trollius coroutines, explicit asynchronous
+    programming, in addition to eventlet greenthreads, implicit asynchronous
+    programming.
+
+    To use the executor, an aioeventlet event loop must the running in the
+    thread executing the executor (usually the main thread). Example of code to
+    setup and run an aioeventlet event loop for the executor (in the main
+    thread):
+
+        import aioeventlet
+        import trollius
+
+        policy = aioeventlet.EventLoopPolicy()
+        trollius.set_event_loop_policy(policy)
+
+        def run_loop(loop):
+            loop.run_forever()
+            loop.close()
+
+        # Get the aioeventlet event loop (create it if needed)
+        loop = trollius.get_event_loop()
+
+        # run the event loop in a new greenthread,
+        # close it when it is done
+        eventlet.spawn(run_loop, loop)
+    """
+
+    def __init__(self, conf, listener, dispatcher):
+        super(AsyncioEventletExecutor, self).__init__(conf, listener,
+                                                      dispatcher)
+        self._loop = None
+
+    def start(self):
+        # check that the event loop is an aioeventlet event loop
+        loop = trollius.get_event_loop()
+        if not isinstance(loop, aioeventlet.EventLoop):
+            raise RuntimeError("need an aioeventlet event loop")
+        self._loop = loop
+
+        super(AsyncioEventletExecutor, self).start()
+
+    def _coroutine_wrapper(self, func, *args, **kw):
+        result = func(*args, **kw)
+        if trollius.iscoroutine(result):
+            result = aioeventlet.yield_future(result, loop=self._loop)
+        return result
+
+    def _dispatch(self, incoming):
+        ctx = self.dispatcher(incoming, self._coroutine_wrapper)
+        impl_eventlet.spawn_with(ctxt=ctx, pool=self._greenpool)
diff --git a/oslo_messaging/_executors/impl_eventlet.py b/oslo_messaging/_executors/impl_eventlet.py
index 555ae03..3333fe7 100644
--- a/oslo_messaging/_executors/impl_eventlet.py
+++ b/oslo_messaging/_executors/impl_eventlet.py
@@ -82,6 +82,9 @@ class EventletExecutor(base.PooledExecutorBase):
                       'behavior. In the future, we will raise a '
                       'RuntimeException in this case.')
 
+    def _dispatch(self, incoming):
+        spawn_with(ctxt=self.dispatcher(incoming), pool=self._greenpool)
+
     def start(self):
         if self._thread is not None:
             return
@@ -92,8 +95,7 @@ class EventletExecutor(base.PooledExecutorBase):
                 while self._running:
                     incoming = self.listener.poll()
                     if incoming is not None:
-                        spawn_with(ctxt=self.dispatcher(incoming),
-                                   pool=self._greenpool)
+                        self._dispatch(incoming)
             except greenlet.GreenletExit:
                 return
 
diff --git a/oslo_messaging/tests/executors/test_executor.py b/oslo_messaging/tests/executors/test_executor.py
index cb321dd..4e3ec51 100644
--- a/oslo_messaging/tests/executors/test_executor.py
+++ b/oslo_messaging/tests/executors/test_executor.py
@@ -17,6 +17,12 @@
 import contextlib
 import threading
 
+# eventlet 0.16 with monkey patching does not work yet on Python 3,
+# so make aioeventlet, eventlet and trollius import optional
+try:
+    import aioeventlet
+except ImportError:
+    aioeventlet = None
 try:
     import eventlet
 except ImportError:
@@ -24,7 +30,16 @@ except ImportError:
 import mock
 import testscenarios
 import testtools
+try:
+    import trollius
+except ImportError:
+    pass
 
+
+try:
+    from oslo_messaging._executors import impl_aioeventlet
+except ImportError:
+    impl_aioeventlet = None
 from oslo_messaging._executors import impl_blocking
 try:
     from oslo_messaging._executors import impl_eventlet
@@ -46,42 +61,110 @@ class TestExecutor(test_utils.BaseTestCase):
         if impl_eventlet is not None:
             impl.append(
                 ('eventlet', dict(executor=impl_eventlet.EventletExecutor)))
+        if impl_aioeventlet is not None:
+            impl.append(
+                ('aioeventlet',
+                 dict(executor=impl_aioeventlet.AsyncioEventletExecutor)))
         cls.scenarios = testscenarios.multiply_scenarios(impl)
 
     @staticmethod
-    def _run_in_thread(executor):
-        def thread():
-            executor.start()
-            executor.wait()
-        thread = threading.Thread(target=thread)
+    def _run_in_thread(target, executor):
+        thread = threading.Thread(target=target, args=(executor,))
         thread.daemon = True
         thread.start()
         thread.join(timeout=30)
 
     def test_executor_dispatch(self):
-        callback = mock.MagicMock(return_value='result')
+        if impl_aioeventlet is not None:
+            aioeventlet_class = impl_aioeventlet.AsyncioEventletExecutor
+        else:
+            aioeventlet_class = None
+        is_aioeventlet = (self.executor == aioeventlet_class)
+
+        if is_aioeventlet:
+            policy = aioeventlet.EventLoopPolicy()
+            trollius.set_event_loop_policy(policy)
+            self.addCleanup(trollius.set_event_loop_policy, None)
+
+            def run_loop(loop):
+                loop.run_forever()
+                loop.close()
+                trollius.set_event_loop(None)
+
+            def run_executor(executor):
+                # create an event loop in the executor thread
+                loop = trollius.new_event_loop()
+                trollius.set_event_loop(loop)
+                eventlet.spawn(run_loop, loop)
+
+                # run the executor
+                executor.start()
+                executor.wait()
+
+                # stop the event loop: run_loop() will close it
+                loop.stop()
+
+            @trollius.coroutine
+            def simple_coroutine(value):
+                yield None
+                raise trollius.Return(value)
+
+            endpoint = mock.MagicMock(return_value=simple_coroutine('result'))
+            event = eventlet.event.Event()
+        else:
+            def run_executor(executor):
+                executor.start()
+                executor.wait()
+
+            endpoint = mock.MagicMock(return_value='result')
 
         class Dispatcher(object):
+            def __init__(self, endpoint):
+                self.endpoint = endpoint
+                self.result = "not set"
+
             @contextlib.contextmanager
-            def __call__(self, incoming):
-                yield lambda: callback(incoming.ctxt, incoming.message)
+            def __call__(self, incoming, executor_callback=None):
+                if executor_callback is not None:
+                    def callback():
+                        result = executor_callback(self.endpoint,
+                                                   incoming.ctxt,
+                                                   incoming.message)
+                        self.result = result
+                        return result
+                    yield callback
+                    event.send()
+                else:
+                    def callback():
+                        result = self.endpoint(incoming.ctxt, incoming.message)
+                        self.result = result
+                        return result
+                    yield callback
 
         listener = mock.Mock(spec=['poll'])
-        executor = self.executor(self.conf, listener, Dispatcher())
+        dispatcher = Dispatcher(endpoint)
+        executor = self.executor(self.conf, listener, dispatcher)
 
         incoming_message = mock.MagicMock(ctxt={},
                                           message={'payload': 'data'})
 
         def fake_poll(timeout=None):
-            if listener.poll.call_count == 1:
-                return incoming_message
-            executor.stop()
+            if is_aioeventlet:
+                if listener.poll.call_count == 1:
+                    return incoming_message
+                event.wait()
+                executor.stop()
+            else:
+                if listener.poll.call_count == 1:
+                    return incoming_message
+                executor.stop()
 
         listener.poll.side_effect = fake_poll
 
-        self._run_in_thread(executor)
+        self._run_in_thread(run_executor, executor)
 
-        callback.assert_called_once_with({}, {'payload': 'data'})
+        endpoint.assert_called_once_with({}, {'payload': 'data'})
+        self.assertEqual(dispatcher.result, 'result')
 
 TestExecutor.generate_scenarios()
 
diff --git a/requirements.txt b/requirements.txt
index 352b14a..e6747b0 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -29,3 +29,7 @@ oslo.middleware>=0.3.0                  # Apache-2.0
 
 # for the futures based executor
 futures>=2.1.6
+
+# needed by the aioeventlet executor
+aioeventlet>=0.4
+trollius>=1.0
diff --git a/setup.cfg b/setup.cfg
index 3f94cb9..0e191c4 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -42,6 +42,7 @@ oslo.messaging.drivers =
     fake = oslo_messaging._drivers.impl_fake:FakeDriver
 
 oslo.messaging.executors =
+    aioeventlet = oslo_messaging._executors.impl_aioeventlet:AsyncioEventletExecutor
     blocking = oslo_messaging._executors.impl_blocking:BlockingExecutor
     eventlet = oslo_messaging._executors.impl_eventlet:EventletExecutor
     threading = oslo_messaging._executors.impl_thread:ThreadExecutor