42a665d06f
To at least try to support things like windows it's better if we can make an attempt to use the platform neutral characters for line separator(s) where appropriate. Change-Id: Icc533ed4d4c94f461b7f19600b74146221f17b18
103 lines
4.0 KiB
Python
103 lines
4.0 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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from __future__ import absolute_import
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import logging
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import os
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import six
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from taskflow import exceptions
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from taskflow.listeners import base
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from taskflow import states
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LOG = logging.getLogger(__name__)
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class CheckingClaimListener(base.Listener):
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"""Listener that interacts [engine, job, jobboard]; ensures claim is valid.
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This listener (or a derivative) can be associated with an engines
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notification system after the job has been claimed (so that the jobs work
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can be worked on by that engine). This listener (after associated) will
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check that the job is still claimed *whenever* the engine notifies of a
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task or flow state change. If the job is not claimed when a state change
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occurs, a associated handler (or the default) will be activated to
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determine how to react to this *hopefully* exceptional case.
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NOTE(harlowja): this may create more traffic than desired to the
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jobboard backend (zookeeper or other), since the amount of state change
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per task and flow is non-zero (and checking during each state change will
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result in quite a few calls to that management system to check the jobs
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claim status); this could be later optimized to check less (or only check
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on a smaller set of states)
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NOTE(harlowja): if a custom ``on_job_loss`` callback is provided it must
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accept three positional arguments, the first being the current engine being
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ran, the second being the 'task/flow' state and the third being the details
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that were sent from the engine to listeners for inspection.
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"""
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def __init__(self, engine, job, board, owner, on_job_loss=None):
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super(CheckingClaimListener, self).__init__(engine)
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self._job = job
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self._board = board
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self._owner = owner
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if on_job_loss is None:
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self._on_job_loss = self._suspend_engine_on_loss
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else:
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if not six.callable(on_job_loss):
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raise ValueError("Custom 'on_job_loss' handler must be"
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" callable")
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self._on_job_loss = on_job_loss
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def _suspend_engine_on_loss(self, engine, state, details):
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"""The default strategy for handling claims being lost."""
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try:
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engine.suspend()
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except exceptions.TaskFlowException as e:
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LOG.warn("Failed suspending engine '%s', (previously owned by"
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" '%s'):%s%s", engine, self._owner, os.linesep,
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e.pformat())
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def _flow_receiver(self, state, details):
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self._claim_checker(state, details)
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def _task_receiver(self, state, details):
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self._claim_checker(state, details)
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def _has_been_lost(self):
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try:
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job_state = self._job.state
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job_owner = self._board.find_owner(self._job)
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except (exceptions.NotFound, exceptions.JobFailure):
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return True
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else:
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if job_state == states.UNCLAIMED or self._owner != job_owner:
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return True
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else:
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return False
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def _claim_checker(self, state, details):
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if not self._has_been_lost():
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LOG.debug("Job '%s' is still claimed (actively owned by '%s')",
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self._job, self._owner)
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else:
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LOG.warn("Job '%s' has lost its claim (previously owned by '%s')",
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self._job, self._owner)
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self._on_job_loss(self._engine, state, details)
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