Send in the prior atom state on notification of a state change

When a retry atom or a task atom changes state it is quite useful
to know the prior state the atom was in; to make this easier pass
that information along in the details about the state transition so
that observers can inspect it if they desire to.

This matches more closely with the flow notification which does
include the prior state (under the details key 'old_state') so this
also increases the uniformity of notifications in general.

Change-Id: I7df1fcc60ba178198776ddaa2681caee5811c4ff

taskflow/engines/action_engine/actions/retry.py

@@ -51,21 +51,24 @@ class RetryAction(object):
         return kwargs
 
     def change_state(self, retry, state, result=None):
+        old_state = self._storage.get_atom_state(retry.name)
         if state in SAVE_RESULT_STATES:
             self._storage.save(retry.name, result, state)
         elif state == states.REVERTED:
             self._storage.cleanup_retry_history(retry.name, state)
         else:
-            old_state = self._storage.get_atom_state(retry.name)
             if state == old_state:
                 # NOTE(imelnikov): nothing really changed, so we should not
                 # write anything to storage and run notifications
                 return
             self._storage.set_atom_state(retry.name, state)
         retry_uuid = self._storage.get_atom_uuid(retry.name)
-        details = dict(retry_name=retry.name,
-                       retry_uuid=retry_uuid,
-                       result=result)
+        details = {
+            'retry_name': retry.name,
+            'retry_uuid': retry_uuid,
+            'result': result,
+            'old_state': old_state,
+        }
         self._notifier.notify(state, details)
 
     def execute(self, retry):

taskflow/engines/action_engine/actions/task.py

@@ -39,11 +39,10 @@ class TaskAction(object):
     def handles(atom):
         return isinstance(atom, task_atom.BaseTask)
 
-    def _is_identity_transition(self, state, task, progress):
+    def _is_identity_transition(self, old_state, state, task, progress):
         if state in SAVE_RESULT_STATES:
             # saving result is never identity transition
             return False
-        old_state = self._storage.get_atom_state(task.name)
         if state != old_state:
             # changing state is not identity transition by definition
             return False
@@ -58,7 +57,8 @@ class TaskAction(object):
         return True
 
     def change_state(self, task, state, result=None, progress=None):
-        if self._is_identity_transition(state, task, progress):
+        old_state = self._storage.get_atom_state(task.name)
+        if self._is_identity_transition(old_state, state, task, progress):
             # NOTE(imelnikov): ignore identity transitions in order
             # to avoid extra write to storage backend and, what's
             # more important, extra notifications
@@ -70,9 +70,12 @@ class TaskAction(object):
         if progress is not None:
             self._storage.set_task_progress(task.name, progress)
         task_uuid = self._storage.get_atom_uuid(task.name)
-        details = dict(task_name=task.name,
-                       task_uuid=task_uuid,
-                       result=result)
+        details = {
+            'task_name': task.name,
+            'task_uuid': task_uuid,
+            'result': result,
+            'old_state': old_state,
+        }
         self._notifier.notify(state, details)
         if progress is not None:
             task.update_progress(progress)