working on deferred callbacks

_pytest/conftest.py

@@ -7,6 +7,7 @@
 
 import pytest
 
+from rasa_nlu import data_router
 from rasa_nlu.components import ComponentBuilder
 from rasa_nlu.config import RasaNLUConfig
 
@@ -16,6 +17,9 @@
 
 CONFIG_DEFAULTS_PATH = "sample_configs/config_defaults.json"
 
+# see `rasa_nlu.data_router` for details. avoids deadlock in `deferred_from_future` function during tests
+data_router.DEFERRED_RUN_IN_REACTOR_THREAD = False
+
 
 @pytest.fixture(scope="session")
 def component_builder():

rasa_nlu/data_router.py

@@ -26,6 +26,13 @@
 
 logger = logging.getLogger(__name__)
 
+# in some execution environments `reactor.callFromThread` can not be called as it will result in a deadlock as
+# the `callFromThread` queues the function to be called by the reactor which only happens after the call to `yield`.
+# Unfortunately, the test is blocked there because `app.flush()` needs to be called to allow the fake server to
+# respond and change the status of the Deferred on which the client is yielding. Solution: during tests we will set
+# this Flag to `False` to directly run the calls instead of wrapping them in `callFromThread`.
+DEFERRED_RUN_IN_REACTOR_THREAD = True
+
 
 def deferred_from_future(future):
     """Converts a concurrent.futures.Future object to a twisted.internet.defer.Deferred obejct.
@@ -36,9 +43,15 @@ def deferred_from_future(future):
     def callback(future):
         e = future.exception()
         if e:
-            reactor.callFromThread(d.errback, e)
-            return
-        reactor.callFromThread(d.callback, future.result())
+            if DEFERRED_RUN_IN_REACTOR_THREAD:
+                reactor.callFromThread(d.errback, e)
+            else:
+                d.errback(e)
+        else:
+            if DEFERRED_RUN_IN_REACTOR_THREAD:
+                reactor.callFromThread(d.callback, future.result())
+            else:
+                d.callback(future.result())
 
     future.add_done_callback(callback)
     return d