Merge "Factor out the on_failure to a mixin type"

taskflow/engines/action_engine/graph_action.py

@@ -16,9 +16,9 @@
 
 from taskflow.engines.action_engine import executor as ex
 from taskflow import exceptions as excp
-from taskflow import retry as r
+from taskflow import retry as retry_atom
 from taskflow import states as st
-from taskflow import task
+from taskflow import task as task_atom
 from taskflow.utils import misc
 
 
@@ -49,9 +49,9 @@ class FutureGraphAction(object):
 
     def _schedule_node(self, node):
         """Schedule a single node for execution."""
-        if isinstance(node, task.BaseTask):
+        if isinstance(node, task_atom.BaseTask):
             return self._schedule_task(node)
-        elif isinstance(node, r.Retry):
+        elif isinstance(node, retry_atom.Retry):
             return self._schedule_retry(node)
         else:
             raise TypeError("Unknown how to schedule node %s" % node)
@@ -108,7 +108,7 @@ class FutureGraphAction(object):
             for future in done:
                 try:
                     node, event, result = future.result()
-                    if isinstance(node, task.BaseTask):
+                    if isinstance(node, task_atom.BaseTask):
                         self._complete_task(node, event, result)
                     if isinstance(result, misc.Failure):
                         if event == ex.EXECUTED:
@@ -185,15 +185,15 @@ class FutureGraphAction(object):
         if retry:
             # Ask retry controller what to do in case of failure
             action = self._retry_action.on_failure(retry, atom, failure)
-            if action == r.RETRY:
+            if action == retry_atom.RETRY:
                 # Prepare subflow for revert
                 self._storage.set_atom_intention(retry.name, st.RETRY)
                 for node in self._analyzer.iterate_subgraph(retry):
                     self._storage.set_atom_intention(node.name, st.REVERT)
-            elif action == r.REVERT:
+            elif action == retry_atom.REVERT:
                 # Ask parent checkpoint
                 self._process_atom_failure(retry, failure)
-            elif action == r.REVERT_ALL:
+            elif action == retry_atom.REVERT_ALL:
                 # Prepare all flow for revert
                 self._revert_all()
         else:
@@ -217,9 +217,9 @@ class FutureGraphAction(object):
 
     def _reset_nodes(self, nodes_iter, intention=st.EXECUTE):
         for node in nodes_iter:
-            if isinstance(node, task.BaseTask):
+            if isinstance(node, task_atom.BaseTask):
                 self._task_action.change_state(node, st.PENDING, progress=0.0)
-            elif isinstance(node, r.Retry):
+            elif isinstance(node, retry_atom.Retry):
                 self._retry_action.change_state(node, st.PENDING)
             else:
                 raise TypeError("Unknown how to reset node %s" % node)

taskflow/retry.py

@@ -26,18 +26,45 @@ from taskflow.utils import misc
 
 LOG = logging.getLogger(__name__)
 
-# Retry actions
+# Decision results.
 REVERT = "REVERT"
 REVERT_ALL = "REVERT_ALL"
 RETRY = "RETRY"
 
 
 @six.add_metaclass(abc.ABCMeta)
-class Retry(atom.Atom):
-    """A base class for retry that controls subflow execution.
-       Retry can be executed multiple times and reverted. On subflow
-       failure it makes a decision about what should be done with the flow
-       (retry, revert to the previous retry, revert the whole flow, etc.).
+class Decider(object):
+    """A base class or mixin for an object that can decide how to resolve
+    execution failures.
+
+    A decider may be executed multiple times on subflow or other atom
+    failure and it is expected to make a decision about what should be done
+    to resolve the failure (retry, revert to the previous retry, revert
+    the whole flow, etc.).
+    """
+
+    @abc.abstractmethod
+    def on_failure(self, history, *args, **kwargs):
+        """On subflow failure makes a decision about the future flow
+        execution using information about prior previous failures (if this
+        historical failure information is not available or was not persisted
+        this history will be empty).
+
+        Returns retry action constant:
+        * 'RETRY' when subflow must be reverted and restarted again (maybe
+          with new parameters).
+        * 'REVERT' when this subflow must be completely reverted and parent
+          subflow should make a decision about the flow execution.
+        * 'REVERT_ALL' in a case when the whole flow must be reverted and
+          marked as FAILURE.
+        """
+
+
+@six.add_metaclass(abc.ABCMeta)
+class Retry(atom.Atom, Decider):
+    """A base class for a retry object that decides how to resolve subflow
+    execution failures and may also provide execute and revert methods to alter
+    the inputs of subflow atoms.
     """
 
     default_provides = None
@@ -78,19 +105,6 @@ class Retry(atom.Atom):
            all subflow's tasks will be reverted before the retry.
         """
 
-    @abc.abstractmethod
-    def on_failure(self, history, *args, **kwargs):
-        """On subflow failure makes a decision about the future flow
-           execution using information about all previous failures.
-           Returns retry action constant:
-           'RETRY' when subflow must be reverted and restarted again (maybe
-           with new parameters).
-           'REVERT' when this subflow must be completely reverted and parent
-           subflow should make a decision about the flow execution.
-           'REVERT_ALL' in a case when the whole flow must be reverted and
-           marked as FAILURE.
-        """
-
 
 class AlwaysRevert(Retry):
     """Retry that always reverts subflow."""