e7df6c66f0
Removed _dead.wait from the stop method and added a wait method to explicitly wait for graceful shutdown. Implicitly waiting for graceful shutdown in the stop method is leading to potential deadlock situations when conductor is running in the main thread and a signal handler is used to kick off stop/shutdown. Also in larger systems, it is desirable to be able to initiate shutdown on all running services then wait/join everything together so as not to force a serial shutdown pattern. Change-Id: Ic74dab22b09100c5b653d12c2518f83a1bf8e859
174 lines
7.3 KiB
Python
174 lines
7.3 KiB
Python
# -*- coding: utf-8 -*-
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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 six
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from taskflow.conductors import base
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from taskflow import exceptions as excp
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from taskflow.listeners import logging as logging_listener
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from taskflow import logging
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from taskflow.types import timing as tt
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from taskflow.utils import async_utils
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from taskflow.utils import deprecation
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from taskflow.utils import threading_utils
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LOG = logging.getLogger(__name__)
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WAIT_TIMEOUT = 0.5
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NO_CONSUME_EXCEPTIONS = tuple([
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excp.ExecutionFailure,
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excp.StorageFailure,
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])
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class SingleThreadedConductor(base.Conductor):
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"""A conductor that runs jobs in its own dispatching loop.
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This conductor iterates over jobs in the provided jobboard (waiting for
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the given timeout if no jobs exist) and attempts to claim them, work on
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those jobs in its local thread (blocking further work from being claimed
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and consumed) and then consume those work units after completetion. This
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process will repeat until the conductor has been stopped or other critical
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error occurs.
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NOTE(harlowja): consumption occurs even if a engine fails to run due to
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a task failure. This is only skipped when an execution failure or
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a storage failure occurs which are *usually* correctable by re-running on
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a different conductor (storage failures and execution failures may be
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transient issues that can be worked around by later execution). If a job
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after completing can not be consumed or abandoned the conductor relies
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upon the jobboard capabilities to automatically abandon these jobs.
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"""
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def __init__(self, name, jobboard, persistence,
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engine=None, engine_options=None, wait_timeout=None):
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super(SingleThreadedConductor, self).__init__(
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name, jobboard, persistence,
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engine=engine, engine_options=engine_options)
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if wait_timeout is None:
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wait_timeout = WAIT_TIMEOUT
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if isinstance(wait_timeout, (int, float) + six.string_types):
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self._wait_timeout = tt.Timeout(float(wait_timeout))
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elif isinstance(wait_timeout, tt.Timeout):
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self._wait_timeout = wait_timeout
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else:
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raise ValueError("Invalid timeout literal: %s" % (wait_timeout))
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self._dead = threading_utils.Event()
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@deprecation.removed_kwarg('timeout')
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def stop(self, timeout=None):
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"""Requests the conductor to stop dispatching.
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This method can be used to request that a conductor stop its
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consumption & dispatching loop.
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The method returns immediately regardless of whether the conductor has
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been stopped.
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:param timeout: This parameter is deprecated and is present for
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backward compatibility. In order to wait for the
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conductor to gracefully shut down, :meth:`wait` should
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be used.
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"""
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self._wait_timeout.interrupt()
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@property
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def dispatching(self):
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return not self._dead.is_set()
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def _dispatch_job(self, job):
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engine = self._engine_from_job(job)
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consume = True
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with logging_listener.LoggingListener(engine, log=LOG):
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LOG.debug("Dispatching engine %s for job: %s", engine, job)
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try:
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engine.run()
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except excp.WrappedFailure as e:
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if all((f.check(*NO_CONSUME_EXCEPTIONS) for f in e)):
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consume = False
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if LOG.isEnabledFor(logging.WARNING):
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if consume:
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LOG.warn("Job execution failed (consumption being"
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" skipped): %s [%s failures]", job, len(e))
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else:
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LOG.warn("Job execution failed (consumption"
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" proceeding): %s [%s failures]", job, len(e))
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# Show the failure/s + traceback (if possible)...
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for i, f in enumerate(e):
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LOG.warn("%s. %s", i + 1, f.pformat(traceback=True))
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except NO_CONSUME_EXCEPTIONS:
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LOG.warn("Job execution failed (consumption being"
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" skipped): %s", job, exc_info=True)
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consume = False
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except Exception:
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LOG.warn("Job execution failed (consumption proceeding): %s",
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job, exc_info=True)
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else:
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LOG.info("Job completed successfully: %s", job)
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return async_utils.make_completed_future(consume)
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def run(self):
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self._dead.clear()
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try:
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while True:
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if self._wait_timeout.is_stopped():
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break
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dispatched = 0
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for job in self._jobboard.iterjobs():
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if self._wait_timeout.is_stopped():
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break
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LOG.debug("Trying to claim job: %s", job)
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try:
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self._jobboard.claim(job, self._name)
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except (excp.UnclaimableJob, excp.NotFound):
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LOG.debug("Job already claimed or consumed: %s", job)
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continue
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consume = False
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try:
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f = self._dispatch_job(job)
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except Exception:
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LOG.warn("Job dispatching failed: %s", job,
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exc_info=True)
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else:
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dispatched += 1
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consume = f.result()
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try:
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if consume:
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self._jobboard.consume(job, self._name)
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else:
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self._jobboard.abandon(job, self._name)
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except excp.JobFailure:
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if consume:
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LOG.warn("Failed job consumption: %s", job,
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exc_info=True)
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else:
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LOG.warn("Failed job abandonment: %s", job,
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exc_info=True)
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if dispatched == 0 and not self._wait_timeout.is_stopped():
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self._wait_timeout.wait()
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finally:
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self._dead.set()
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def wait(self, timeout=None):
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"""Waits for the conductor to gracefully exit.
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This method waits for the conductor to gracefully exit. An optional
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timeout can be provided, which will cause the method to return
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within the specified timeout. If the timeout is reached, the returned
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value will be False.
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:param timeout: Maximum number of seconds that the :meth:`wait` method
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should block for.
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"""
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return self._dead.wait(timeout)
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