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# vim: tabstop=4 shiftwidth=4 softtabstop=4
#
# 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.
from openstack.common import log as logging
from openstack.common.gettextutils import _
LOG = logging.getLogger(__name__)
def periodic_task(*args, **kwargs):
"""Decorator to indicate that a method is a periodic task.
This decorator can be used in two ways:
1. Without arguments '@periodic_task', this will be run on every tick
of the periodic scheduler.
2. With arguments, @periodic_task(ticks_between_runs=N), this will be
run on every N ticks of the periodic scheduler.
"""
def decorator(f):
f._periodic_task = True
f._ticks_between_runs = kwargs.pop('ticks_between_runs', 0)
return f
# NOTE(sirp): The `if` is necessary to allow the decorator to be used with
# and without parens.
#
# In the 'with-parens' case (with kwargs present), this function needs to
# return a decorator function since the interpreter will invoke it like:
#
# periodic_task(*args, **kwargs)(f)
#
# In the 'without-parens' case, the original function will be passed
# in as the first argument, like:
#
# periodic_task(f)
if kwargs:
return decorator
else:
return decorator(args[0])
class _PeriodicTasksMeta(type):
def __init__(cls, names, bases, dict_):
"""Metaclass that allows us to collect decorated periodic tasks."""
super(_PeriodicTasksMeta, cls).__init__(names, bases, dict_)
# NOTE(sirp): if the attribute is not present then we must be the base
# class, so, go ahead and initialize it. If the attribute is present,
# then we're a subclass so make a copy of it so we don't step on our
# parent's toes.
try:
cls._periodic_tasks = cls._periodic_tasks[:]
except AttributeError:
cls._periodic_tasks = []
try:
cls._ticks_to_skip = cls._ticks_to_skip.copy()
except AttributeError:
cls._ticks_to_skip = {}
# This uses __dict__ instead of
# inspect.getmembers(cls, inspect.ismethod) so only the methods of the
# current class are added when this class is scanned, and base classes
# are not added redundantly.
for value in cls.__dict__.values():
if getattr(value, '_periodic_task', False):
task = value
name = task.__name__
cls._periodic_tasks.append((name, task))
cls._ticks_to_skip[name] = task._ticks_between_runs
class PeriodicTasks(object):
__metaclass__ = _PeriodicTasksMeta
def run_periodic_tasks(self, *args, **kwargs):
"""Tasks to be run at a periodic interval."""
raise_on_error = kwargs.get('raise_on_error', False)
for task_name, task in self._periodic_tasks:
full_task_name = '.'.join([self.__class__.__name__, task_name])
ticks_to_skip = self._ticks_to_skip[task_name]
if ticks_to_skip > 0:
LOG.debug(_("Skipping %(full_task_name)s, %(ticks_to_skip)s"
" ticks left until next run"), locals())
self._ticks_to_skip[task_name] -= 1
continue
self._ticks_to_skip[task_name] = task._ticks_between_runs
LOG.debug(_("Running periodic task %(full_task_name)s"), locals())
try:
task(self, *args, **kwargs)
except Exception as e:
if raise_on_error:
raise
LOG.exception(_("Error during %(full_task_name)s: %(e)s"),
locals())
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