openstack/deb-python-taskflow
Code Issues Proposed changes

Make resolution/retry strategies more clear and better

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This adds a separate method which is used to locate the
action and handler callback that will be used to resolve
the failure. This also adjusts the consultation of the
parent retry (if any) to ensure that we handle the no
parent retry case correctly.

Once a decision has been made; return it and add logging
that shows what is being activated and how many nodes were
affected by the resolution strategy (which can be useful to
know during debugging).

Change-Id: I28101765fce000dd7c56b7c3a1fbcf1a4315799b
This commit is contained in:
Joshua Harlow
2015-04-06 11:49:16 -07:00
parent 56bf4ac332
commit 8910cdbfd0
3 changed files with 116 additions and 33 deletions
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6
taskflow/engines/action_engine/analyzer.py
View File

@@ -125,9 +125,9 @@ class Analyzer(object):
return all(state in (st.PENDING, st.REVERTED)
for state, intention in six.itervalues(task_states))
def iterate_subgraph(self, retry):
"""Iterates a subgraph connected to given retry controller."""
for _src, dst in traversal.dfs_edges(self._execution_graph, retry):
def iterate_subgraph(self, atom):
"""Iterates a subgraph connected to given atom."""
for _src, dst in traversal.dfs_edges(self._execution_graph, atom):
yield dst
def iterate_retries(self, state=None):

131
taskflow/engines/action_engine/completer.py
View File

@@ -14,14 +14,81 @@
# License for the specific language governing permissions and limitations
# under the License.
import abc
import weakref
from oslo_utils import reflection
import six
from taskflow.engines.action_engine import executor as ex
from taskflow import logging
from taskflow import retry as retry_atom
from taskflow import states as st
from taskflow import task as task_atom
from taskflow.types import failure
LOG = logging.getLogger(__name__)
@six.add_metaclass(abc.ABCMeta)
class _Strategy(object):
"""Local/internal helper strategy base object"""
def __init__(self, runtime):
self._runtime = runtime
def __str__(self):
base = reflection.get_class_name(self, fully_qualified=False)
return base + "(strategy=%s)" % (self.strategy.name)
class _RevertAndRetry(_Strategy):
"""Sets the *associated* subflow for revert to be later retried."""
strategy = retry_atom.RETRY
def __init__(self, runtime, retry):
super(_RevertAndRetry, self).__init__(runtime)
self._retry = retry
def apply(self):
tweaked = self._runtime.reset_nodes([self._retry], state=None,
intention=st.RETRY)
tweaked.extend(self._runtime.reset_subgraph(self._retry, state=None,
intention=st.REVERT))
return tweaked
class _RevertAll(_Strategy):
"""Sets *all* nodes/atoms to the ``REVERT`` intention."""
strategy = retry_atom.REVERT_ALL
def __init__(self, runtime):
super(_RevertAll, self).__init__(runtime)
self._analyzer = runtime.analyzer
def apply(self):
return self._runtime.reset_nodes(self._analyzer.iterate_all_nodes(),
state=None, intention=st.REVERT)
class _Revert(_Strategy):
"""Sets atom and *associated* nodes to the ``REVERT`` intention."""
strategy = retry_atom.REVERT
def __init__(self, runtime, atom):
super(_Revert, self).__init__(runtime)
self._atom = atom
def apply(self):
tweaked = self._runtime.reset_nodes([self._atom], state=None,
intention=st.REVERT)
tweaked.extend(self._runtime.reset_subgraph(self._atom, state=None,
intention=st.REVERT))
return tweaked
class Completer(object):
"""Completes atoms using actions to complete them."""
@@ -32,6 +99,7 @@ class Completer(object):
self._retry_action = runtime.retry_action
self._storage = runtime.storage
self._task_action = runtime.task_action
self._undefined_resolver = _RevertAll(self._runtime)
def _complete_task(self, task, event, result):
"""Completes the given task, processes task failure."""
@@ -77,6 +145,32 @@ class Completer(object):
return True
return False
def _determine_resolution(self, atom, failure):
"""Determines which resolution strategy to activate/apply."""
retry = self._analyzer.find_atom_retry(atom)
if retry is not None:
# Ask retry controller what to do in case of failure.
strategy = self._retry_action.on_failure(retry, atom, failure)
if strategy == retry_atom.RETRY:
return _RevertAndRetry(self._runtime, retry)
elif strategy == retry_atom.REVERT:
# Ask parent retry and figure out what to do...
parent_resolver = self._determine_resolution(retry, failure)
# Ok if the parent resolver says something not REVERT, and
# it isn't just using the undefined resolver, assume the
# parent knows best.
if parent_resolver is not self._undefined_resolver:
if parent_resolver.strategy != retry_atom.REVERT:
return parent_resolver
return _Revert(self._runtime, retry)
elif strategy == retry_atom.REVERT_ALL:
return _RevertAll(self._runtime)
else:
raise ValueError("Unknown atom failure resolution"
" action/strategy '%s'" % strategy)
else:
return self._undefined_resolver
def _process_atom_failure(self, atom, failure):
"""Processes atom failure & applies resolution strategies.
@@ -86,30 +180,15 @@ class Completer(object):
then adjust the needed other atoms intentions, and states, ... so that
the failure can be worked around.
"""
retry = self._analyzer.find_atom_retry(atom)
if retry is not None:
# Ask retry controller what to do in case of failure
action = self._retry_action.on_failure(retry, atom, failure)
if action == retry_atom.RETRY:
# Prepare just the surrounding subflow for revert to be later
# retried...
self._storage.set_atom_intention(retry.name, st.RETRY)
self._runtime.reset_subgraph(retry, state=None,
intention=st.REVERT)
elif action == retry_atom.REVERT:
# Ask parent checkpoint.
self._process_atom_failure(retry, failure)
elif action == retry_atom.REVERT_ALL:
# Prepare all flow for revert
self._revert_all()
else:
raise ValueError("Unknown atom failure resolution"
" action '%s'" % action)
resolver = self._determine_resolution(atom, failure)
LOG.debug("Applying resolver '%s' to resolve failure '%s'"
" of atom '%s'", resolver, failure, atom)
tweaked = resolver.apply()
# Only show the tweaked node list when blather is on, otherwise
# just show the amount/count of nodes tweaks...
if LOG.isEnabledFor(logging.BLATHER):
LOG.blather("Modified/tweaked %s nodes while applying"
" resolver '%s'", tweaked, resolver)
else:
# Prepare all flow for revert
self._revert_all()
def _revert_all(self):
"""Attempts to set all nodes to the REVERT intention."""
self._runtime.reset_nodes(self._analyzer.iterate_all_nodes(),
state=None, intention=st.REVERT)
LOG.debug("Modified/tweaked %s nodes while applying"
" resolver '%s'", len(tweaked), resolver)

12
taskflow/engines/action_engine/runtime.py
View File

@@ -97,7 +97,10 @@ class Runtime(object):
# consumption...
def reset_nodes(self, nodes, state=st.PENDING, intention=st.EXECUTE):
tweaked = []
for node in nodes:
if state or intention:
tweaked.append((node, state, intention))
if state:
if self.task_action.handles(node):
self.task_action.change_state(node, state,
@@ -109,14 +112,15 @@ class Runtime(object):
% (node, type(node)))
if intention:
self.storage.set_atom_intention(node.name, intention)
return tweaked
def reset_all(self, state=st.PENDING, intention=st.EXECUTE):
self.reset_nodes(self.analyzer.iterate_all_nodes(),
state=state, intention=intention)
return self.reset_nodes(self.analyzer.iterate_all_nodes(),
state=state, intention=intention)
def reset_subgraph(self, node, state=st.PENDING, intention=st.EXECUTE):
self.reset_nodes(self.analyzer.iterate_subgraph(node),
state=state, intention=intention)
return self.reset_nodes(self.analyzer.iterate_subgraph(node),
state=state, intention=intention)
def retry_subflow(self, retry):
self.storage.set_atom_intention(retry.name, st.EXECUTE)