Source code for taskflow.conductors.backends.impl_blocking

# -*- coding: utf-8 -*-

#    Licensed under the Apache License, Version 2.0 (the "License"); you may
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#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
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#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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#    under the License.

import threading

try:
    from contextlib import ExitStack  # noqa
except ImportError:
    from contextlib2 import ExitStack  # noqa

from debtcollector import removals
from oslo_utils import excutils
import six

from taskflow.conductors import base
from taskflow import exceptions as excp
from taskflow.listeners import logging as logging_listener
from taskflow import logging
from taskflow.types import timing as tt
from taskflow.utils import async_utils

LOG = logging.getLogger(__name__)
WAIT_TIMEOUT = 0.5
NO_CONSUME_EXCEPTIONS = tuple([
    excp.ExecutionFailure,
    excp.StorageFailure,
])


[docs]class BlockingConductor(base.Conductor): """A conductor that runs jobs in its own dispatching loop. This conductor iterates over jobs in the provided jobboard (waiting for the given timeout if no jobs exist) and attempts to claim them, work on those jobs in its local thread (blocking further work from being claimed and consumed) and then consume those work units after completetion. This process will repeat until the conductor has been stopped or other critical error occurs. NOTE(harlowja): consumption occurs even if a engine fails to run due to a task failure. This is only skipped when an execution failure or a storage failure occurs which are *usually* correctable by re-running on a different conductor (storage failures and execution failures may be transient issues that can be worked around by later execution). If a job after completing can not be consumed or abandoned the conductor relies upon the jobboard capabilities to automatically abandon these jobs. """ START_FINISH_EVENTS_EMITTED = tuple([ 'compilation', 'preparation', 'validation', 'running', ]) """Events will be emitted for the start and finish of each engine activity defined above, the actual event name that can be registered to subscribe to will be ``${event}_start`` and ``${event}_end`` where the ``${event}`` in this pseudo-variable will be one of these events. """ def __init__(self, name, jobboard, persistence=None, engine=None, engine_options=None, wait_timeout=None): super(BlockingConductor, self).__init__( name, jobboard, persistence=persistence, engine=engine, engine_options=engine_options) if wait_timeout is None: wait_timeout = WAIT_TIMEOUT if isinstance(wait_timeout, (int, float) + six.string_types): self._wait_timeout = tt.Timeout(float(wait_timeout)) elif isinstance(wait_timeout, tt.Timeout): self._wait_timeout = wait_timeout else: raise ValueError("Invalid timeout literal: %s" % (wait_timeout)) self._dead = threading.Event() @removals.removed_kwarg('timeout', version="0.8", removal_version="2.0")
[docs] def stop(self, timeout=None): """Requests the conductor to stop dispatching. This method can be used to request that a conductor stop its consumption & dispatching loop. The method returns immediately regardless of whether the conductor has been stopped. .. deprecated:: 0.8 The ``timeout`` parameter is **deprecated** and is present for backward compatibility **only**. In order to wait for the conductor to gracefully shut down, :py:meth:`wait` should be used instead. """ self._wait_timeout.interrupt()
@property def dispatching(self): return not self._dead.is_set() def _listeners_from_job(self, job, engine): listeners = super(BlockingConductor, self)._listeners_from_job(job, engine) listeners.append(logging_listener.LoggingListener(engine, log=LOG)) return listeners def _dispatch_job(self, job): engine = self._engine_from_job(job) listeners = self._listeners_from_job(job, engine) with ExitStack() as stack: for listener in listeners: stack.enter_context(listener) LOG.debug("Dispatching engine for job '%s'", job) consume = True try: for stage_func, event_name in [(engine.compile, 'compilation'), (engine.prepare, 'preparation'), (engine.validate, 'validation'), (engine.run, 'running')]: self._notifier.notify("%s_start" % event_name, { 'job': job, 'engine': engine, 'conductor': self, }) stage_func() self._notifier.notify("%s_end" % event_name, { 'job': job, 'engine': engine, 'conductor': self, }) except excp.WrappedFailure as e: if all((f.check(*NO_CONSUME_EXCEPTIONS) for f in e)): consume = False if LOG.isEnabledFor(logging.WARNING): if consume: LOG.warn("Job execution failed (consumption being" " skipped): %s [%s failures]", job, len(e)) else: LOG.warn("Job execution failed (consumption" " proceeding): %s [%s failures]", job, len(e)) # Show the failure/s + traceback (if possible)... for i, f in enumerate(e): LOG.warn("%s. %s", i + 1, f.pformat(traceback=True)) except NO_CONSUME_EXCEPTIONS: LOG.warn("Job execution failed (consumption being" " skipped): %s", job, exc_info=True) consume = False except Exception: LOG.warn("Job execution failed (consumption proceeding): %s", job, exc_info=True) else: LOG.info("Job completed successfully: %s", job) return async_utils.make_completed_future(consume) def run(self): self._dead.clear() try: while True: if self._wait_timeout.is_stopped(): break dispatched = 0 for job in self._jobboard.iterjobs(): if self._wait_timeout.is_stopped(): break LOG.debug("Trying to claim job: %s", job) try: self._jobboard.claim(job, self._name) except (excp.UnclaimableJob, excp.NotFound): LOG.debug("Job already claimed or consumed: %s", job) continue consume = False try: f = self._dispatch_job(job) except KeyboardInterrupt: with excutils.save_and_reraise_exception(): LOG.warn("Job dispatching interrupted: %s", job) except Exception: LOG.warn("Job dispatching failed: %s", job, exc_info=True) else: dispatched += 1 consume = f.result() try: if consume: self._jobboard.consume(job, self._name) else: self._jobboard.abandon(job, self._name) except (excp.JobFailure, excp.NotFound): if consume: LOG.warn("Failed job consumption: %s", job, exc_info=True) else: LOG.warn("Failed job abandonment: %s", job, exc_info=True) if dispatched == 0 and not self._wait_timeout.is_stopped(): self._wait_timeout.wait() finally: self._dead.set()
[docs] def wait(self, timeout=None): """Waits for the conductor to gracefully exit. This method waits for the conductor to gracefully exit. An optional timeout can be provided, which will cause the method to return within the specified timeout. If the timeout is reached, the returned value will be False. :param timeout: Maximum number of seconds that the :meth:`wait` method should block for. """ return self._dead.wait(timeout)