# -*- coding: utf-8 -*- # Copyright (C) 2012 Yahoo! Inc. All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); you may # not use this file except in compliance with the License. You may obtain # a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the # License for the specific language governing permissions and limitations # under the License. import weakref from automaton import machines from taskflow import logging from taskflow import states as st from taskflow.types import failure from taskflow.utils import iter_utils # Default waiting state timeout (in seconds). WAITING_TIMEOUT = 60 # Meta states the state machine uses. UNDEFINED = 'UNDEFINED' GAME_OVER = 'GAME_OVER' META_STATES = (GAME_OVER, UNDEFINED) # Event name constants the state machine uses. SCHEDULE = 'schedule_next' WAIT = 'wait_finished' ANALYZE = 'examine_finished' FINISH = 'completed' FAILED = 'failed' SUSPENDED = 'suspended' SUCCESS = 'success' REVERTED = 'reverted' START = 'start' LOG = logging.getLogger(__name__) class MachineMemory(object): """State machine memory.""" def __init__(self): self.next_up = set() self.not_done = set() self.failures = [] self.done = set() class MachineBuilder(object): """State machine *builder* that powers the engine components. NOTE(harlowja): the machine (states and events that will trigger transitions) that this builds is represented by the following table:: +--------------+------------------+------------+----------+---------+ | Start | Event | End | On Enter | On Exit | +--------------+------------------+------------+----------+---------+ | ANALYZING | completed | GAME_OVER | . | . | | ANALYZING | schedule_next | SCHEDULING | . | . | | ANALYZING | wait_finished | WAITING | . | . | | FAILURE[$] | . | . | . | . | | GAME_OVER | failed | FAILURE | . | . | | GAME_OVER | reverted | REVERTED | . | . | | GAME_OVER | success | SUCCESS | . | . | | GAME_OVER | suspended | SUSPENDED | . | . | | RESUMING | schedule_next | SCHEDULING | . | . | | REVERTED[$] | . | . | . | . | | SCHEDULING | wait_finished | WAITING | . | . | | SUCCESS[$] | . | . | . | . | | SUSPENDED[$] | . | . | . | . | | UNDEFINED[^] | start | RESUMING | . | . | | WAITING | examine_finished | ANALYZING | . | . | +--------------+------------------+------------+----------+---------+ Between any of these yielded states (minus ``GAME_OVER`` and ``UNDEFINED``) if the engine has been suspended or the engine has failed (due to a non-resolveable task failure or scheduling failure) the machine will stop executing new tasks (currently running tasks will be allowed to complete) and this machines run loop will be broken. NOTE(harlowja): If the runtimes scheduler component is able to schedule tasks in parallel, this enables parallel running and/or reversion. """ def __init__(self, runtime, waiter): self._runtime = weakref.proxy(runtime) self._analyzer = runtime.analyzer self._completer = runtime.completer self._scheduler = runtime.scheduler self._storage = runtime.storage self._waiter = waiter def build(self, timeout=None): """Builds a state-machine (that is used during running).""" memory = MachineMemory() if timeout is None: timeout = WAITING_TIMEOUT # Cache some local functions/methods... do_complete = self._completer.complete do_complete_failure = self._completer.complete_failure get_atom_intention = self._storage.get_atom_intention def do_schedule(next_nodes): return self._scheduler.schedule( sorted(next_nodes, key=lambda node: getattr(node, 'priority', 0), reverse=True)) def is_runnable(): # Checks if the storage says the flow is still runnable... return self._storage.get_flow_state() == st.RUNNING def iter_next_atoms(atom=None, apply_deciders=True): # Yields and filters and tweaks the next atoms to run... maybe_atoms_it = self._analyzer.iter_next_atoms(atom=atom) for atom, late_decider in maybe_atoms_it: if apply_deciders: proceed = late_decider.check_and_affect(self._runtime) if proceed: yield atom else: yield atom def resume(old_state, new_state, event): # This reaction function just updates the state machines memory # to include any nodes that need to be executed (from a previous # attempt, which may be empty if never ran before) and any nodes # that are now ready to be ran. memory.next_up.update( iter_utils.unique_seen((self._completer.resume(), iter_next_atoms()))) return SCHEDULE def game_over(old_state, new_state, event): # This reaction function is mainly a intermediary delegation # function that analyzes the current memory and transitions to # the appropriate handler that will deal with the memory values, # it is *always* called before the final state is entered. if memory.failures: return FAILED leftover_atoms = iter_utils.count( # Avoid activating the deciders, since at this point # the engine is finishing and there will be no more further # work done anyway... iter_next_atoms(apply_deciders=False)) if leftover_atoms: # Ok we didn't finish (either reverting or executing...) so # that means we must of been stopped at some point... LOG.trace("Suspension determined to have been reacted to" " since (at least) %s atoms have been left in an" " unfinished state", leftover_atoms) return SUSPENDED elif self._analyzer.is_success(): return SUCCESS else: return REVERTED def schedule(old_state, new_state, event): # This reaction function starts to schedule the memory's next # nodes (iff the engine is still runnable, which it may not be # if the user of this engine has requested the engine/storage # that holds this information to stop or suspend); handles failures # that occur during this process safely... if is_runnable() and memory.next_up: not_done, failures = do_schedule(memory.next_up) if not_done: memory.not_done.update(not_done) if failures: memory.failures.extend(failures) memory.next_up.intersection_update(not_done) return WAIT def complete_an_atom(fut): # This completes a single atom saving its result in # storage and preparing whatever predecessors or successors will # now be ready to execute (or revert or retry...); it also # handles failures that occur during this process safely... atom = fut.atom try: outcome, result = fut.result() do_complete(atom, outcome, result) if isinstance(result, failure.Failure): retain = do_complete_failure(atom, outcome, result) if retain: memory.failures.append(result) else: # NOTE(harlowja): avoid making any intention request # to storage unless we are sure we are in DEBUG # enabled logging (otherwise we will call this all # the time even when DEBUG is not enabled, which # would suck...) if LOG.isEnabledFor(logging.DEBUG): intention = get_atom_intention(atom.name) LOG.debug("Discarding failure '%s' (in response" " to outcome '%s') under completion" " units request during completion of" " atom '%s' (intention is to %s)", result, outcome, atom, intention) except Exception: memory.failures.append(failure.Failure()) LOG.exception("Engine '%s' atom post-completion failed", atom) def wait(old_state, new_state, event): # TODO(harlowja): maybe we should start doing 'yield from' this # call sometime in the future, or equivalent that will work in # py2 and py3. if memory.not_done: done, not_done = self._waiter(memory.not_done, timeout=timeout) memory.done.update(done) memory.not_done = not_done return ANALYZE def analyze(old_state, new_state, event): # This reaction function is responsible for analyzing all nodes # that have finished executing/reverting and figuring # out what nodes are now ready to be ran (and then triggering those # nodes to be scheduled in the future); handles failures that # occur during this process safely... next_up = set() while memory.done: fut = memory.done.pop() # Force it to be completed so that we can ensure that # before we iterate over any successors or predecessors # that we know it has been completed and saved and so on... complete_an_atom(fut) if not memory.failures: atom = fut.atom try: more_work = set(iter_next_atoms(atom=atom)) except Exception: memory.failures.append(failure.Failure()) LOG.exception("Engine '%s' atom post-completion" " next atom searching failed", atom) else: next_up.update(more_work) if is_runnable() and next_up and not memory.failures: memory.next_up.update(next_up) return SCHEDULE elif memory.not_done: return WAIT else: return FINISH def on_exit(old_state, event): LOG.debug("Exiting old state '%s' in response to event '%s'", old_state, event) def on_enter(new_state, event): LOG.debug("Entering new state '%s' in response to event '%s'", new_state, event) # NOTE(harlowja): when ran in trace mode it is quite useful # to track the various state transitions as they happen... watchers = {} if LOG.isEnabledFor(logging.TRACE): watchers['on_exit'] = on_exit watchers['on_enter'] = on_enter m = machines.FiniteMachine() m.add_state(GAME_OVER, **watchers) m.add_state(UNDEFINED, **watchers) m.add_state(st.ANALYZING, **watchers) m.add_state(st.RESUMING, **watchers) m.add_state(st.REVERTED, terminal=True, **watchers) m.add_state(st.SCHEDULING, **watchers) m.add_state(st.SUCCESS, terminal=True, **watchers) m.add_state(st.SUSPENDED, terminal=True, **watchers) m.add_state(st.WAITING, **watchers) m.add_state(st.FAILURE, terminal=True, **watchers) m.default_start_state = UNDEFINED m.add_transition(GAME_OVER, st.REVERTED, REVERTED) m.add_transition(GAME_OVER, st.SUCCESS, SUCCESS) m.add_transition(GAME_OVER, st.SUSPENDED, SUSPENDED) m.add_transition(GAME_OVER, st.FAILURE, FAILED) m.add_transition(UNDEFINED, st.RESUMING, START) m.add_transition(st.ANALYZING, GAME_OVER, FINISH) m.add_transition(st.ANALYZING, st.SCHEDULING, SCHEDULE) m.add_transition(st.ANALYZING, st.WAITING, WAIT) m.add_transition(st.RESUMING, st.SCHEDULING, SCHEDULE) m.add_transition(st.SCHEDULING, st.WAITING, WAIT) m.add_transition(st.WAITING, st.ANALYZING, ANALYZE) m.add_reaction(GAME_OVER, FINISH, game_over) m.add_reaction(st.ANALYZING, ANALYZE, analyze) m.add_reaction(st.RESUMING, START, resume) m.add_reaction(st.SCHEDULING, SCHEDULE, schedule) m.add_reaction(st.WAITING, WAIT, wait) m.freeze() return (m, memory)