Add support for using daemon threads (fixes #14)

docs/changes.rst

@@ -3,7 +3,7 @@ Changes
 =======
 
 
-v1.0.2 (in development)
+v1.1.0 (in development)
 =======================
 
 - An exception raised in :meth:`pykka.Actor.on_start` didn't stop the actor
@@ -12,6 +12,10 @@ v1.0.2 (in development)
 - Make sure exceptions in :meth:`pykka.Actor.on_stop` and
   :meth:`pykka.Actor.on_failure` is logged.
 
+- Add :attr:`pykka.ThreadingActor.use_daemon_thread` flag for optionally
+  running an actor on a daemon thread, so that it doesn't block the Python
+  program from exiting. (Fixes: :issue:`14`)
+
 
 v1.0.1 (2012-12-12)
 ===================

pykka/actor.py

@@ -326,6 +326,22 @@ class ThreadingActor(Actor):
     threads that are not Pykka actors.
     """
 
+    use_daemon_thread = False
+    """
+    A boolean value indicating whether this actor is executed on a thread that
+    is a daemon thread (:class:`True`) or not (:class:`False`). This must be
+    set before :meth:`pykka.Actor.start` is called, otherwise
+    :exc:`RuntimeError` is raised.
+
+    The entire Python program exits when no alive non-daemon threads are left.
+    This means that an actor running on a daemon thread may be interrupted at
+    any time, and there is no guarantee that cleanup will be done or that
+    :meth:`pykka.Actor.on_stop` will be called.
+
+    Actors do not inherit the daemon flag from the actor that made it. It
+    always has to be set explicitly for the actor to run on a daemonic thread.
+    """
+
     @staticmethod
     def _create_actor_inbox():
         return _queue.Queue()
@@ -337,6 +353,7 @@ def _create_future():
     def _start_actor_loop(self):
         thread = _threading.Thread(target=self._actor_loop)
         thread.name = thread.name.replace('Thread', self.__class__.__name__)
+        thread.daemon = self.use_daemon_thread
         thread.start()
 
 

tests/actor_test.py

@@ -298,13 +298,32 @@ class FailingOnFailureActor(FailingOnFailureActor, ThreadingActor):
     class SuperInitActor(ThreadingActor):
         pass
 
+    class DaemonActor(ThreadingActor):
+        use_daemon_thread = True
+
     def test_actor_thread_is_named_after_pykka_actor_class(self):
         alive_threads = threading.enumerate()
         alive_thread_names = [t.name for t in alive_threads]
         named_correctly = [
             name.startswith(AnActor.__name__) for name in alive_thread_names]
         self.assert_(any(named_correctly))
 
+    def test_actor_thread_is_not_daemonic_by_default(self):
+        alive_threads = threading.enumerate()
+        actor_threads = [
+            t for t in alive_threads if t.name.startswith('AnActor')]
+        self.assertEqual(1, len(actor_threads))
+        self.assertFalse(actor_threads[0].daemon)
+
+    def test_actor_thread_is_daemonic_if_use_daemon_thread_flag_is_set(self):
+        actor_ref = self.DaemonActor.start()
+        alive_threads = threading.enumerate()
+        actor_threads = [
+            t for t in alive_threads if t.name.startswith('DaemonActor')]
+        self.assertEqual(1, len(actor_threads))
+        self.assertTrue(actor_threads[0].daemon)
+        actor_ref.stop()
+
 
 if HAS_GEVENT:
     class GeventActorTest(ActorTest, unittest.TestCase):