Merge "Have the storage class provide a 'change_flow_state' method"

taskflow/engines/action_engine/engine.py

@@ -171,7 +171,6 @@ class ActionEngine(base.Engine):
         self._compilation = None
         self._compiler = compiler.PatternCompiler(flow)
         self._lock = threading.RLock()
-        self._state_lock = threading.RLock()
         self._storage_ensured = False
         self._validated = False
         # Retries are not *currently* executed out of the engines process
@@ -362,18 +361,15 @@ class ActionEngine(base.Engine):
         return compilation
 
     def _change_state(self, state):
-        with self._state_lock:
-            old_state = self.storage.get_flow_state()
-            if not states.check_flow_transition(old_state, state):
-                return
-            self.storage.set_flow_state(state)
-        details = {
-            'engine': self,
-            'flow_name': self.storage.flow_name,
-            'flow_uuid': self.storage.flow_uuid,
-            'old_state': old_state,
-        }
-        self.notifier.notify(state, details)
+        moved, old_state = self.storage.change_flow_state(state)
+        if moved:
+            details = {
+                'engine': self,
+                'flow_name': self.storage.flow_name,
+                'flow_uuid': self.storage.flow_uuid,
+                'old_state': old_state,
+            }
+            self.notifier.notify(state, details)
 
     def _ensure_storage(self):
         """Ensure all contained atoms exist in the storage unit."""

taskflow/storage.py

@@ -1117,6 +1117,21 @@ class Storage(object):
             clone.meta.update(update_with)
             self._with_connection(self._save_flow_detail, source, clone)
 
+    @fasteners.write_locked
+    def change_flow_state(self, state):
+        """Transition flow from old state to new state.
+
+        Returns ``(True, old_state)`` if transition was performed,
+        or ``(False, old_state)`` if it was ignored, or raises a
+        :py:class:`~taskflow.exceptions.InvalidState` exception if transition
+        is invalid.
+        """
+        old_state = self.get_flow_state()
+        if not states.check_flow_transition(old_state, state):
+            return (False, old_state)
+        self.set_flow_state(state)
+        return (True, old_state)
+
     @fasteners.read_locked
     def get_flow_state(self):
         """Get state from flow details."""