Merge "Use the enum library for the retry strategy enumerations"

doc/source/atoms.rst

@@ -58,20 +58,11 @@ associated `scope`_).
 
 Currently derivatives of the :py:class:`retry <taskflow.retry.Retry>` base
 class must provide a :py:func:`~taskflow.retry.Retry.on_failure` method to
-determine how a failure should be handled.
+determine how a failure should be handled. The current enumeration(s) that can
+be returned from the :py:func:`~taskflow.retry.Retry.on_failure` method
+are defined in an enumeration class described here:
 
-The current enumeration set that can be returned from this method is:
-
-* ``RETRY`` - retries the surrounding subflow (a retry object is associated
-  with a flow, which is typically converted into a graph hierarchy at
-  compilation time) again.
-
-* ``REVERT`` - reverts only the surrounding subflow but *consult* the
-  parent atom before doing this to determine if the parent retry object
-  provides a different reconciliation strategy (retry atoms can be nested, this
-  is possible since flows themselves can be nested).
-
-* ``REVERT_ALL`` - completely reverts a whole flow.
+.. autoclass:: taskflow.retry.Decision
 
 To aid in the reconciliation process the
 :py:class:`retry <taskflow.retry.Retry>` base class also mandates
@@ -177,7 +168,13 @@ Interfaces
 ==========
 
 .. automodule:: taskflow.task
-.. automodule:: taskflow.retry
+.. autoclass:: taskflow.retry.Retry
+.. autoclass:: taskflow.retry.History
+.. autoclass:: taskflow.retry.AlwaysRevert
+.. autoclass:: taskflow.retry.AlwaysRevertAll
+.. autoclass:: taskflow.retry.Times
+.. autoclass:: taskflow.retry.ForEach
+.. autoclass:: taskflow.retry.ParameterizedForEach
 
 Hierarchy
 =========
@@ -185,5 +182,10 @@ Hierarchy
 .. inheritance-diagram::
     taskflow.atom
     taskflow.task
-    taskflow.retry
+    taskflow.retry.Retry
+    taskflow.retry.AlwaysRevert
+    taskflow.retry.AlwaysRevertAll
+    taskflow.retry.Times
+    taskflow.retry.ForEach
+    taskflow.retry.ParameterizedForEach
     :parts: 1

requirements-py2.txt

@@ -13,6 +13,9 @@ ordereddict
 # Python 2->3 compatibility library.
 six>=1.9.0
 
+# Enum library made for <= python 3.3
+enum34
+
 # Very nice graph library
 networkx>=1.8
 

requirements-py3.txt

@@ -10,6 +10,9 @@ pbr>=0.6,!=0.7,<1.0
 # Python 2->3 compatibility library.
 six>=1.9.0
 
+# Enum library made for <= python 3.3
+enum34
+
 # Very nice graph library
 networkx>=1.8
 

taskflow/retry.py

@@ -17,16 +17,38 @@
 
 import abc
 
+import enum
 import six
 
 from taskflow import atom
 from taskflow import exceptions as exc
 from taskflow.utils import misc
 
-# Decision results.
-REVERT = "REVERT"
-REVERT_ALL = "REVERT_ALL"
-RETRY = "RETRY"
+
+@enum.unique
+class Decision(misc.StrEnum):
+    """Decision results/strategy enumeration."""
+
+    REVERT = "REVERT"
+    """Reverts only the surrounding/associated subflow.
+
+    This strategy first consults the parent atom before reverting the
+    associated subflow to determine if the parent retry object provides a
+    different reconciliation strategy (if no parent retry object exists
+    then reverting will proceed, if one does exist the parent retry may
+    override this reconciliation strategy with its own).
+    """
+
+    #: Completely reverts the whole flow.
+    REVERT_ALL = "REVERT_ALL"
+
+    #: Retries the surrounding/associated subflow again.
+    RETRY = "RETRY"
+
+# Retain these aliases for a number of releases...
+REVERT = Decision.REVERT
+REVERT_ALL = Decision.REVERT_ALL
+RETRY = Decision.RETRY
 
 # Constants passed into revert/execute kwargs.
 #
@@ -108,14 +130,16 @@ class Retry(atom.Atom):
 
     This abstract base class is used to inherit from and provide different
     strategies that will be activated upon execution failures. Since a retry
-    object is an atom it may also provide :meth:`.execute` and
-    :meth:`.revert` methods to alter the inputs of connected atoms (depending
-    on the desired strategy to be used this can be quite useful).
+    object is an atom it may also provide :meth:`~taskflow.retry.Retry.execute`
+    and :meth:`~taskflow.retry.Retry.revert` methods to alter the inputs of
+    connected atoms (depending on the desired strategy to be used this can be
+    quite useful).
 
-    NOTE(harlowja): the :meth:`.execute` and :meth:`.revert` and
-    :meth:`.on_failure` will automatically be given a ``history`` parameter,
-    which contains information about the past decisions and outcomes
-    that have occurred (if available).
+    NOTE(harlowja): the :meth:`~taskflow.retry.Retry.execute` and
+    :meth:`~taskflow.retry.Retry.revert` and
+    :meth:`~taskflow.retry.Retry.on_failure` will automatically be given
+    a ``history`` parameter, which contains information about the past
+    decisions and outcomes that have occurred (if available).
     """
 
     default_provides = None

taskflow/utils/misc.py

@@ -26,6 +26,7 @@ import threading
 import time
 import types
 
+import enum
 from oslo_serialization import jsonutils
 from oslo_utils import importutils
 from oslo_utils import netutils
@@ -57,6 +58,17 @@ _MONOTONIC_LOCATIONS = tuple([
 ])
 
 
+class StrEnum(str, enum.Enum):
+    """An enumeration that is also a string and can be compared to strings."""
+
+    def __new__(cls, *args, **kwargs):
+        for a in args:
+            if not isinstance(a, str):
+                raise TypeError("Enumeration '%s' (%s) is not"
+                                " a string" % (a, type(a).__name__))
+        return super(StrEnum, cls).__new__(cls, *args, **kwargs)
+
+
 def find_monotonic(allow_time_time=False):
     """Tries to find a monotonic time providing function (and returns it)."""
     for import_str in _MONOTONIC_LOCATIONS: