70e58977c9
In situations where many atoms can execute at the same time it is sometimes useful to denote that when this situation happens that certain atoms should execute/revert before other atoms (or at least an attempt should be made to do this) instead of being nearly arbitrary. This adds a priority class attribute to the atom class (which can be overridden or changed as needed) which is then used in the runtime state machine to sort on so that atoms with higher priority get submitted (and therefore executed/reverted) first. Closes-Bug: #1507755 Change-Id: I3dcc705959085cba167883c85278e394b5cb1d2b
289 lines
12 KiB
Python
289 lines
12 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2012 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 weakref
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from automaton import machines
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from taskflow import logging
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from taskflow import states as st
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from taskflow.types import failure
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from taskflow.utils import iter_utils
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# Default waiting state timeout (in seconds).
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WAITING_TIMEOUT = 60
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# Meta states the state machine uses.
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UNDEFINED = 'UNDEFINED'
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GAME_OVER = 'GAME_OVER'
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META_STATES = (GAME_OVER, UNDEFINED)
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# Event name constants the state machine uses.
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SCHEDULE = 'schedule_next'
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WAIT = 'wait_finished'
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ANALYZE = 'examine_finished'
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FINISH = 'completed'
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FAILED = 'failed'
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SUSPENDED = 'suspended'
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SUCCESS = 'success'
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REVERTED = 'reverted'
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START = 'start'
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LOG = logging.getLogger(__name__)
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class MachineMemory(object):
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"""State machine memory."""
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def __init__(self):
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self.next_up = set()
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self.not_done = set()
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self.failures = []
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self.done = set()
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class MachineBuilder(object):
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"""State machine *builder* that powers the engine components.
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NOTE(harlowja): the machine (states and events that will trigger
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transitions) that this builds is represented by the following
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table::
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+--------------+------------------+------------+----------+---------+
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| Start | Event | End | On Enter | On Exit |
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+--------------+------------------+------------+----------+---------+
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| ANALYZING | completed | GAME_OVER | . | . |
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| ANALYZING | schedule_next | SCHEDULING | . | . |
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| ANALYZING | wait_finished | WAITING | . | . |
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| FAILURE[$] | . | . | . | . |
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| GAME_OVER | failed | FAILURE | . | . |
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| GAME_OVER | reverted | REVERTED | . | . |
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| GAME_OVER | success | SUCCESS | . | . |
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| GAME_OVER | suspended | SUSPENDED | . | . |
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| RESUMING | schedule_next | SCHEDULING | . | . |
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| REVERTED[$] | . | . | . | . |
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| SCHEDULING | wait_finished | WAITING | . | . |
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| SUCCESS[$] | . | . | . | . |
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| SUSPENDED[$] | . | . | . | . |
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| UNDEFINED[^] | start | RESUMING | . | . |
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| WAITING | examine_finished | ANALYZING | . | . |
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+--------------+------------------+------------+----------+---------+
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Between any of these yielded states (minus ``GAME_OVER`` and ``UNDEFINED``)
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if the engine has been suspended or the engine has failed (due to a
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non-resolveable task failure or scheduling failure) the machine will stop
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executing new tasks (currently running tasks will be allowed to complete)
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and this machines run loop will be broken.
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NOTE(harlowja): If the runtimes scheduler component is able to schedule
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tasks in parallel, this enables parallel running and/or reversion.
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"""
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def __init__(self, runtime, waiter):
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self._runtime = weakref.proxy(runtime)
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self._analyzer = runtime.analyzer
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self._completer = runtime.completer
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self._scheduler = runtime.scheduler
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self._storage = runtime.storage
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self._waiter = waiter
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def build(self, timeout=None):
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"""Builds a state-machine (that is used during running)."""
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memory = MachineMemory()
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if timeout is None:
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timeout = WAITING_TIMEOUT
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# Cache some local functions/methods...
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do_complete = self._completer.complete
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def do_schedule(next_nodes):
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return self._scheduler.schedule(
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sorted(next_nodes,
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key=lambda node: getattr(node, 'priority', 0),
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reverse=True))
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def is_runnable():
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# Checks if the storage says the flow is still runnable...
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return self._storage.get_flow_state() == st.RUNNING
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def iter_next_atoms(atom=None, apply_deciders=True):
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# Yields and filters and tweaks the next atoms to run...
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maybe_atoms_it = self._analyzer.iter_next_atoms(atom=atom)
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for atom, late_decider in maybe_atoms_it:
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if apply_deciders:
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proceed = late_decider.check_and_affect(self._runtime)
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if proceed:
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yield atom
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else:
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yield atom
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def resume(old_state, new_state, event):
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# This reaction function just updates the state machines memory
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# to include any nodes that need to be executed (from a previous
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# attempt, which may be empty if never ran before) and any nodes
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# that are now ready to be ran.
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memory.next_up.update(
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iter_utils.unique_seen(self._completer.resume(),
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iter_next_atoms()))
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return SCHEDULE
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def game_over(old_state, new_state, event):
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# This reaction function is mainly a intermediary delegation
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# function that analyzes the current memory and transitions to
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# the appropriate handler that will deal with the memory values,
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# it is *always* called before the final state is entered.
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if memory.failures:
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return FAILED
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leftover_atoms = iter_utils.count(
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# Avoid activating the deciders, since at this point
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# the engine is finishing and there will be no more further
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# work done anyway...
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iter_next_atoms(apply_deciders=False))
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if leftover_atoms:
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# Ok we didn't finish (either reverting or executing...) so
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# that means we must of been stopped at some point...
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LOG.blather("Suspension determined to have been reacted to"
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" since (at least) %s atoms have been left in an"
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" unfinished state", leftover_atoms)
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return SUSPENDED
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elif self._analyzer.is_success():
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return SUCCESS
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else:
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return REVERTED
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def schedule(old_state, new_state, event):
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# This reaction function starts to schedule the memory's next
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# nodes (iff the engine is still runnable, which it may not be
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# if the user of this engine has requested the engine/storage
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# that holds this information to stop or suspend); handles failures
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# that occur during this process safely...
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if is_runnable() and memory.next_up:
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not_done, failures = do_schedule(memory.next_up)
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if not_done:
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memory.not_done.update(not_done)
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if failures:
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memory.failures.extend(failures)
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memory.next_up.intersection_update(not_done)
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return WAIT
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def wait(old_state, new_state, event):
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# TODO(harlowja): maybe we should start doing 'yield from' this
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# call sometime in the future, or equivalent that will work in
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# py2 and py3.
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if memory.not_done:
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done, not_done = self._waiter(memory.not_done, timeout=timeout)
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memory.done.update(done)
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memory.not_done = not_done
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return ANALYZE
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def analyze(old_state, new_state, event):
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# This reaction function is responsible for analyzing all nodes
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# that have finished executing and completing them and figuring
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# out what nodes are now ready to be ran (and then triggering those
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# nodes to be scheduled in the future); handles failures that
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# occur during this process safely...
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next_up = set()
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while memory.done:
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fut = memory.done.pop()
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atom = fut.atom
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try:
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outcome, result = fut.result()
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retain = do_complete(atom, outcome, result)
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if isinstance(result, failure.Failure):
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if retain:
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memory.failures.append(result)
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else:
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# NOTE(harlowja): avoid making any
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# intention request to storage unless we are
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# sure we are in DEBUG enabled logging (otherwise
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# we will call this all the time even when DEBUG
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# is not enabled, which would suck...)
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if LOG.isEnabledFor(logging.DEBUG):
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intention = self._storage.get_atom_intention(
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atom.name)
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LOG.debug("Discarding failure '%s' (in"
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" response to outcome '%s') under"
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" completion units request during"
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" completion of atom '%s' (intention"
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" is to %s)", result, outcome,
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atom, intention)
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except Exception:
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memory.failures.append(failure.Failure())
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else:
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try:
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more_work = set(iter_next_atoms(atom=atom))
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except Exception:
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memory.failures.append(failure.Failure())
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else:
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next_up.update(more_work)
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if is_runnable() and next_up and not memory.failures:
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memory.next_up.update(next_up)
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return SCHEDULE
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elif memory.not_done:
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return WAIT
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else:
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return FINISH
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def on_exit(old_state, event):
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LOG.debug("Exiting old state '%s' in response to event '%s'",
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old_state, event)
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def on_enter(new_state, event):
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LOG.debug("Entering new state '%s' in response to event '%s'",
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new_state, event)
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# NOTE(harlowja): when ran in blather mode it is quite useful
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# to track the various state transitions as they happen...
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watchers = {}
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if LOG.isEnabledFor(logging.BLATHER):
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watchers['on_exit'] = on_exit
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watchers['on_enter'] = on_enter
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m = machines.FiniteMachine()
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m.add_state(GAME_OVER, **watchers)
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m.add_state(UNDEFINED, **watchers)
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m.add_state(st.ANALYZING, **watchers)
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m.add_state(st.RESUMING, **watchers)
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m.add_state(st.REVERTED, terminal=True, **watchers)
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m.add_state(st.SCHEDULING, **watchers)
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m.add_state(st.SUCCESS, terminal=True, **watchers)
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m.add_state(st.SUSPENDED, terminal=True, **watchers)
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m.add_state(st.WAITING, **watchers)
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m.add_state(st.FAILURE, terminal=True, **watchers)
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m.default_start_state = UNDEFINED
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m.add_transition(GAME_OVER, st.REVERTED, REVERTED)
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m.add_transition(GAME_OVER, st.SUCCESS, SUCCESS)
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m.add_transition(GAME_OVER, st.SUSPENDED, SUSPENDED)
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m.add_transition(GAME_OVER, st.FAILURE, FAILED)
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m.add_transition(UNDEFINED, st.RESUMING, START)
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m.add_transition(st.ANALYZING, GAME_OVER, FINISH)
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m.add_transition(st.ANALYZING, st.SCHEDULING, SCHEDULE)
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m.add_transition(st.ANALYZING, st.WAITING, WAIT)
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m.add_transition(st.RESUMING, st.SCHEDULING, SCHEDULE)
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m.add_transition(st.SCHEDULING, st.WAITING, WAIT)
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m.add_transition(st.WAITING, st.ANALYZING, ANALYZE)
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m.add_reaction(GAME_OVER, FINISH, game_over)
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m.add_reaction(st.ANALYZING, ANALYZE, analyze)
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m.add_reaction(st.RESUMING, START, resume)
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m.add_reaction(st.SCHEDULING, SCHEDULE, schedule)
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m.add_reaction(st.WAITING, WAIT, wait)
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m.freeze()
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return (m, memory)
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