40cf88e55c
Since we have put a warning on the engine components docs saying they should not be used externally it seems ok to make these more visible so that people reading the docs can follow more of how it works (and the components involved there-in). Depends-On: I0f07858e96ea3baf46f8a453e253b9ed29c7f7e2 Depends-On: I33bd2d9dff9cb7dc1a50177db7286b7317966784 Change-Id: I24d5cbfd47aa786ffab923243b97c7ae43b2f21f
205 lines
7.8 KiB
Python
205 lines
7.8 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2014 Yahoo! Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import abc
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import weakref
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from oslo_utils import reflection
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import six
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from taskflow.engines.action_engine import executor as ex
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from taskflow import logging
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from taskflow import retry as retry_atom
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from taskflow import states as st
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from taskflow import task as task_atom
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from taskflow.types import failure
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LOG = logging.getLogger(__name__)
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@six.add_metaclass(abc.ABCMeta)
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class Strategy(object):
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"""Failure resolution strategy base class."""
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strategy = None
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def __init__(self, runtime):
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self._runtime = runtime
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@abc.abstractmethod
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def apply(self):
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"""Applies some algorithm to resolve some detected failure."""
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def __str__(self):
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base = reflection.get_class_name(self, fully_qualified=False)
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if self.strategy is not None:
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strategy_name = self.strategy.name
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else:
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strategy_name = "???"
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return base + "(strategy=%s)" % (strategy_name)
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class RevertAndRetry(Strategy):
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"""Sets the *associated* subflow for revert to be later retried."""
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strategy = retry_atom.RETRY
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def __init__(self, runtime, retry):
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super(RevertAndRetry, self).__init__(runtime)
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self._retry = retry
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def apply(self):
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tweaked = self._runtime.reset_nodes([self._retry], state=None,
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intention=st.RETRY)
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tweaked.extend(self._runtime.reset_subgraph(self._retry, state=None,
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intention=st.REVERT))
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return tweaked
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class RevertAll(Strategy):
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"""Sets *all* nodes/atoms to the ``REVERT`` intention."""
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strategy = retry_atom.REVERT_ALL
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def __init__(self, runtime):
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super(RevertAll, self).__init__(runtime)
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self._analyzer = runtime.analyzer
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def apply(self):
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return self._runtime.reset_nodes(self._analyzer.iterate_all_nodes(),
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state=None, intention=st.REVERT)
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class Revert(Strategy):
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"""Sets atom and *associated* nodes to the ``REVERT`` intention."""
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strategy = retry_atom.REVERT
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def __init__(self, runtime, atom):
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super(Revert, self).__init__(runtime)
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self._atom = atom
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def apply(self):
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tweaked = self._runtime.reset_nodes([self._atom], state=None,
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intention=st.REVERT)
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tweaked.extend(self._runtime.reset_subgraph(self._atom, state=None,
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intention=st.REVERT))
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return tweaked
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class Completer(object):
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"""Completes atoms using actions to complete them."""
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def __init__(self, runtime):
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self._runtime = weakref.proxy(runtime)
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self._analyzer = runtime.analyzer
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self._retry_action = runtime.retry_action
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self._storage = runtime.storage
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self._task_action = runtime.task_action
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self._undefined_resolver = RevertAll(self._runtime)
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def _complete_task(self, task, event, result):
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"""Completes the given task, processes task failure."""
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if event == ex.EXECUTED:
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self._task_action.complete_execution(task, result)
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else:
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self._task_action.complete_reversion(task, result)
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def resume(self):
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"""Resumes nodes in the contained graph.
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This is done to allow any previously completed or failed nodes to
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be analyzed, there results processed and any potential nodes affected
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to be adjusted as needed.
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This should return a set of nodes which should be the initial set of
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nodes that were previously not finished (due to a RUNNING or REVERTING
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attempt not previously finishing).
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"""
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for node in self._analyzer.iterate_all_nodes():
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if self._analyzer.get_state(node) == st.FAILURE:
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self._process_atom_failure(node, self._storage.get(node.name))
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for retry in self._analyzer.iterate_retries(st.RETRYING):
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self._runtime.retry_subflow(retry)
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unfinished_nodes = set()
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for node in self._analyzer.iterate_all_nodes():
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if self._analyzer.get_state(node) in (st.RUNNING, st.REVERTING):
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unfinished_nodes.add(node)
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return unfinished_nodes
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def complete(self, node, event, result):
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"""Performs post-execution completion of a node.
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Returns whether the result should be saved into an accumulator of
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failures or whether this should not be done.
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"""
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if isinstance(node, task_atom.BaseTask):
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self._complete_task(node, event, result)
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if isinstance(result, failure.Failure):
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if event == ex.EXECUTED:
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self._process_atom_failure(node, result)
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else:
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return True
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return False
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def _determine_resolution(self, atom, failure):
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"""Determines which resolution strategy to activate/apply."""
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retry = self._analyzer.find_atom_retry(atom)
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if retry is not None:
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# Ask retry controller what to do in case of failure.
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strategy = self._retry_action.on_failure(retry, atom, failure)
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if strategy == retry_atom.RETRY:
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return RevertAndRetry(self._runtime, retry)
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elif strategy == retry_atom.REVERT:
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# Ask parent retry and figure out what to do...
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parent_resolver = self._determine_resolution(retry, failure)
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# Ok if the parent resolver says something not REVERT, and
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# it isn't just using the undefined resolver, assume the
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# parent knows best.
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if parent_resolver is not self._undefined_resolver:
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if parent_resolver.strategy != retry_atom.REVERT:
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return parent_resolver
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return Revert(self._runtime, retry)
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elif strategy == retry_atom.REVERT_ALL:
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return RevertAll(self._runtime)
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else:
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raise ValueError("Unknown atom failure resolution"
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" action/strategy '%s'" % strategy)
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else:
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return self._undefined_resolver
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def _process_atom_failure(self, atom, failure):
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"""Processes atom failure & applies resolution strategies.
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On atom failure this will find the atoms associated retry controller
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and ask that controller for the strategy to perform to resolve that
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failure. After getting a resolution strategy decision this method will
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then adjust the needed other atoms intentions, and states, ... so that
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the failure can be worked around.
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"""
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resolver = self._determine_resolution(atom, failure)
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LOG.debug("Applying resolver '%s' to resolve failure '%s'"
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" of atom '%s'", resolver, failure, atom)
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tweaked = resolver.apply()
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# Only show the tweaked node list when blather is on, otherwise
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# just show the amount/count of nodes tweaks...
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if LOG.isEnabledFor(logging.BLATHER):
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LOG.blather("Modified/tweaked %s nodes while applying"
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" resolver '%s'", tweaked, resolver)
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else:
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LOG.debug("Modified/tweaked %s nodes while applying"
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" resolver '%s'", len(tweaked), resolver)
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