Pass stack to thread in resource_signal

This is the only thread that gets started without an explicit reference to
the stack. This prevents us from using a weakref in the resource, as it
will cause the Stack's reference count to hit 0 before the thread is run.
Now we explicitly pass a reference to the stack.

Change-Id: Ie51be7b54d97ef184e401e395a7e7e3a26ce003b
Related-Bug: #1454873

heat/engine/service.py

@@ -1173,8 +1173,7 @@ class EngineService(service.Service):
                           implementation.
         '''
 
-        def _resource_signal(rsrc, details):
-            stack = rsrc.stack
+        def _resource_signal(stack, rsrc, details):
             LOG.debug("signaling resource %s:%s" % (stack.name, rsrc.name))
             rsrc.signal(details)
 
@@ -1199,11 +1198,11 @@ class EngineService(service.Service):
         rsrc = stack[resource_name]
         if callable(rsrc.signal):
             if sync_call:
-                _resource_signal(rsrc, details)
+                _resource_signal(stack, rsrc, details)
                 return rsrc.metadata_get()
             else:
                 self.thread_group_mgr.start(stack.id, _resource_signal,
-                                            rsrc, details)
+                                            stack, rsrc, details)
 
     @context.request_context
     def find_physical_resource(self, cnxt, physical_resource_id):

heat/tests/test_engine_service.py

@@ -2935,6 +2935,7 @@ class StackServiceTest(common.HeatTestCase):
         self.eng.thread_group_mgr.groups[stack.id] = tools.DummyThreadGroup()
         self.m.StubOutWithMock(self.eng.thread_group_mgr, 'start')
         self.eng.thread_group_mgr.start(stack.id,
+                                        mox.IgnoreArg(),
                                         mox.IgnoreArg(),
                                         mox.IgnoreArg(),
                                         mox.IgnoreArg()).AndReturn(None)