206 lines
7.4 KiB
Python
206 lines
7.4 KiB
Python
# vim: tabstop=4 shiftwidth=4 softtabstop=4
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# Copyright 2010 United States Government as represented by the
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# Administrator of the National Aeronautics and Space Administration.
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# 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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"""Base Manager class.
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Managers are responsible for a certain aspect of the system. It is a logical
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grouping of code relating to a portion of the system. In general other
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components should be using the manager to make changes to the components that
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it is responsible for.
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For example, other components that need to deal with volumes in some way,
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should do so by calling methods on the VolumeManager instead of directly
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changing fields in the database. This allows us to keep all of the code
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relating to volumes in the same place.
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We have adopted a basic strategy of Smart managers and dumb data, which means
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rather than attaching methods to data objects, components should call manager
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methods that act on the data.
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Methods on managers that can be executed locally should be called directly. If
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a particular method must execute on a remote host, this should be done via rpc
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to the service that wraps the manager
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Managers should be responsible for most of the db access, and
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non-implementation specific data. Anything implementation specific that can't
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be generalized should be done by the Driver.
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In general, we prefer to have one manager with multiple drivers for different
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implementations, but sometimes it makes sense to have multiple managers. You
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can think of it this way: Abstract different overall strategies at the manager
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level(FlatNetwork vs VlanNetwork), and different implementations at the driver
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level(LinuxNetDriver vs CiscoNetDriver).
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Managers will often provide methods for initial setup of a host or periodic
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tasks to a wrapping service.
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This module provides Manager, a base class for managers.
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"""
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from nova.db import base
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from nova import flags
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from nova import log as logging
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from nova.scheduler import api
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from nova import version
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FLAGS = flags.FLAGS
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LOG = logging.getLogger('nova.manager')
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def periodic_task(*args, **kwargs):
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"""Decorator to indicate that a method is a periodic task.
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This decorator can be used in two ways:
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1. Without arguments '@periodic_task', this will be run on every tick
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of the periodic scheduler.
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2. With arguments, @periodic_task(ticks_between_runs=N), this will be
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run on every N ticks of the periodic scheduler.
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"""
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def decorator(f):
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f._periodic_task = True
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f._ticks_between_runs = kwargs.pop('ticks_between_runs', 0)
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return f
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# NOTE(sirp): The `if` is necessary to allow the decorator to be used with
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# and without parens.
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#
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# In the 'with-parens' case (with kwargs present), this function needs to
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# return a decorator function since the interpreter will invoke it like:
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#
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# periodic_task(*args, **kwargs)(f)
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#
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# In the 'without-parens' case, the original function will be passed
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# in as the first argument, like:
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#
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# periodic_task(f)
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if kwargs:
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return decorator
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else:
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return decorator(args[0])
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class ManagerMeta(type):
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def __init__(cls, names, bases, dict_):
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"""Metaclass that allows us to collect decorated periodic tasks."""
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super(ManagerMeta, cls).__init__(names, bases, dict_)
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# NOTE(sirp): if the attribute is not present then we must be the base
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# class, so, go ahead an initialize it. If the attribute is present,
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# then we're a subclass so make a copy of it so we don't step on our
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# parent's toes.
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try:
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cls._periodic_tasks = cls._periodic_tasks[:]
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except AttributeError:
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cls._periodic_tasks = []
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try:
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cls._ticks_to_skip = cls._ticks_to_skip.copy()
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except AttributeError:
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cls._ticks_to_skip = {}
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for value in cls.__dict__.values():
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if getattr(value, '_periodic_task', False):
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task = value
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name = task.__name__
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cls._periodic_tasks.append((name, task))
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cls._ticks_to_skip[name] = task._ticks_between_runs
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class Manager(base.Base):
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__metaclass__ = ManagerMeta
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def __init__(self, host=None, db_driver=None):
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if not host:
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host = FLAGS.host
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self.host = host
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super(Manager, self).__init__(db_driver)
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def periodic_tasks(self, context, raise_on_error=False):
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"""Tasks to be run at a periodic interval."""
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for task_name, task in self._periodic_tasks:
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full_task_name = '.'.join([self.__class__.__name__, task_name])
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ticks_to_skip = self._ticks_to_skip[task_name]
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if ticks_to_skip > 0:
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LOG.debug(_("Skipping %(full_task_name)s, %(ticks_to_skip)s"
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" ticks left until next run"), locals())
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self._ticks_to_skip[task_name] -= 1
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continue
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self._ticks_to_skip[task_name] = task._ticks_between_runs
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LOG.debug(_("Running periodic task %(full_task_name)s"), locals())
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try:
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task(self, context)
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except Exception as e:
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if raise_on_error:
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raise
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LOG.exception(_("Error during %(full_task_name)s: %(e)s"),
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locals())
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def init_host(self):
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"""Handle initialization if this is a standalone service.
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Child classes should override this method.
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"""
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pass
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def service_version(self, context):
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return version.version_string()
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def service_config(self, context):
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config = {}
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for key in FLAGS:
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config[key] = FLAGS.get(key, None)
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return config
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class SchedulerDependentManager(Manager):
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"""Periodically send capability updates to the Scheduler services.
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Services that need to update the Scheduler of their capabilities
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should derive from this class. Otherwise they can derive from
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manager.Manager directly. Updates are only sent after
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update_service_capabilities is called with non-None values.
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"""
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def __init__(self, host=None, db_driver=None, service_name='undefined'):
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self.last_capabilities = None
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self.service_name = service_name
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super(SchedulerDependentManager, self).__init__(host, db_driver)
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def update_service_capabilities(self, capabilities):
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"""Remember these capabilities to send on next periodic update."""
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self.last_capabilities = capabilities
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@periodic_task
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def _publish_service_capabilities(self, context):
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"""Pass data back to the scheduler at a periodic interval."""
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if self.last_capabilities:
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LOG.debug(_('Notifying Schedulers of capabilities ...'))
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api.update_service_capabilities(context, self.service_name,
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self.host, self.last_capabilities)
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