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OpenStack Study: loopingcall.py

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# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2010 United States Government as represented by the

# Administrator of the National Aeronautics and Space Administration.

# Copyright 2011 Justin Santa Barbara

# 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 sys

from eventlet import event

from eventlet import greenthread

from glance.openstack.common.gettextutils import _

from glance.openstack.common import log as logging

from glance.openstack.common import timeutils

LOG = logging.getLogger(__name__)

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class LoopingCallDone(Exception):

"""Exception to break out and stop a LoopingCall.

The poll-function passed to LoopingCall can raise this exception to

break out of the loop normally. This is somewhat analogous to

StopIteration.

An optional return-value can be included as the argument to the exception;

this return-value will be returned by LoopingCall.wait()

"""

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    def __init__(self, retvalue=True):

        """:param retvalue: Value that LoopingCall.wait() should return."""

        self.retvalue = retvalue

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class LoopingCallBase(object):

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    def __init__(self, f=None, *args, **kw):

        self.args = args

        self.kw = kw

        self.f = f

        self._running = False

        self.done = None

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    def stop(self):

        self._running = False

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    def wait(self):

        return self.done.wait()

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class FixedIntervalLoopingCall(LoopingCallBase):

"""A fixed interval looping call."""

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    def start(self, interval, initial_delay=None):

        self._running = True

        done = event.Event()

        def _inner():

            if initial_delay:

                greenthread.sleep(initial_delay)

            try:

                while self._running:

                    start = timeutils.utcnow()

                    self.f(*self.args, **self.kw)

                    end = timeutils.utcnow()

                    if not self._running:

                        break

                    delay = interval - timeutils.delta_seconds(start, end)

                    if delay <= 0:

                        LOG.warn(_('task run outlasted interval by %s sec') %

                                 -delay)

                    greenthread.sleep(delay if delay > 0 else 0)

            except LoopingCallDone as e:

                self.stop()

                done.send(e.retvalue)

            except Exception:

                LOG.exception(_('in fixed duration looping call'))

                done.send_exception(*sys.exc_info())

                return

            else:

                done.send(True)

        self.done = done

        greenthread.spawn_n(_inner)

        return self.done

# TODO(mikal): this class name is deprecated in Havana and should be removed

# in the I release

LoopingCall = FixedIntervalLoopingCall

**** CubicPower OpenStack Study ****

        def _inner():

            if initial_delay:

                greenthread.sleep(initial_delay)

            try:

                while self._running:

                    start = timeutils.utcnow()

                    self.f(*self.args, **self.kw)

                    end = timeutils.utcnow()

                    if not self._running:

                        break

                    delay = interval - timeutils.delta_seconds(start, end)

                    if delay <= 0:

                        LOG.warn(_('task run outlasted interval by %s sec') %

                                 -delay)

                    greenthread.sleep(delay if delay > 0 else 0)

            except LoopingCallDone as e:

                self.stop()

                done.send(e.retvalue)

            except Exception:

                LOG.exception(_('in fixed duration looping call'))

                done.send_exception(*sys.exc_info())

                return

            else:

                done.send(True)

        self.done = done

        greenthread.spawn_n(_inner)

        return self.done

# TODO(mikal): this class name is deprecated in Havana and should be removed

# in the I release

LoopingCall = FixedIntervalLoopingCall

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class DynamicLoopingCall(LoopingCallBase):

"""A looping call which sleeps until the next known event.

The function called should return how long to sleep for before being

called again.

"""

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    def start(self, initial_delay=None, periodic_interval_max=None):

        self._running = True

        done = event.Event()

        def _inner():

            if initial_delay:

                greenthread.sleep(initial_delay)

            try:

                while self._running:

                    idle = self.f(*self.args, **self.kw)

                    if not self._running:

                        break

                    if periodic_interval_max is not None:

                        idle = min(idle, periodic_interval_max)

                    LOG.debug(_('Dynamic looping call sleeping for %.02f '

                                'seconds'), idle)

                    greenthread.sleep(idle)

            except LoopingCallDone as e:

                self.stop()

                done.send(e.retvalue)

            except Exception:

                LOG.exception(_('in dynamic looping call'))

                done.send_exception(*sys.exc_info())

                return

            else:

                done.send(True)

        self.done = done

        greenthread.spawn(_inner)

        return self.done

**** CubicPower OpenStack Study ****

        def _inner():

            if initial_delay:

                greenthread.sleep(initial_delay)

            try:

                while self._running:

                    idle = self.f(*self.args, **self.kw)

                    if not self._running:

                        break

                    if periodic_interval_max is not None:

                        idle = min(idle, periodic_interval_max)

                    LOG.debug(_('Dynamic looping call sleeping for %.02f '

                                'seconds'), idle)

                    greenthread.sleep(idle)

            except LoopingCallDone as e:

                self.stop()

                done.send(e.retvalue)

            except Exception:

                LOG.exception(_('in dynamic looping call'))

                done.send_exception(*sys.exc_info())

                return

            else:

                done.send(True)

        self.done = done

        greenthread.spawn(_inner)

        return self.done