cf69c5b4c3
This patch addresses the issue by removing the extra nesting
(which is effectively redundant).
The longer story about this patch is the following:
Race conditions may cause DBDuplicateEntry exceptions that
require a transaction to be rollbacked back, and yet make
the whole operation succeed. A classic example is what has
been solved in commit fbc6b99. If the rollback is done in a
nested transaction, the above mentioned exception is raised.
To address the problem, we could use savepoints by means of
sqlalchemy's begin_nested(); Even though this approach is
preferable, it causes quite a bit of changes in the unit
tests (because of sqlite); it may also require that certain
DBMS, or certain DB backend configurations, support savepoints.
In the end, the simpler approach was chosen.
Closes-bug: #1354072
Change-Id: Ic9393319e55f71d681124bd3052e939724ebab6b
247 lines
11 KiB
Python
247 lines
11 KiB
Python
# Copyright (c) 2013 OpenStack Foundation.
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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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import abc
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import random
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from oslo.db import exception as db_exc
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import six
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from sqlalchemy.orm import exc
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from sqlalchemy import sql
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from neutron.common import constants
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from neutron.db import agents_db
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from neutron.db import l3_agentschedulers_db
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from neutron.db import l3_db
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from neutron.openstack.common import log as logging
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LOG = logging.getLogger(__name__)
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@six.add_metaclass(abc.ABCMeta)
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class L3Scheduler(object):
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@abc.abstractmethod
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def schedule(self, plugin, context, router_id,
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candidates=None, hints=None):
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"""Schedule the router to an active L3 agent.
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Schedule the router only if it is not already scheduled.
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"""
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pass
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def dvr_has_binding(self, context, router_id, l3_agent_id):
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router_binding_model = l3_agentschedulers_db.RouterL3AgentBinding
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query = context.session.query(router_binding_model)
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query = query.filter(router_binding_model.router_id == router_id,
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router_binding_model.l3_agent_id == l3_agent_id)
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return query.count() > 0
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def auto_schedule_routers(self, plugin, context, host, router_ids):
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"""Schedule non-hosted routers to L3 Agent running on host.
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If router_ids is given, each router in router_ids is scheduled
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if it is not scheduled yet. Otherwise all unscheduled routers
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are scheduled.
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Don't schedule the routers which are hosted already
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by active l3 agents.
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"""
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with context.session.begin(subtransactions=True):
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# query if we have valid l3 agent on the host
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query = context.session.query(agents_db.Agent)
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query = query.filter(agents_db.Agent.agent_type ==
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constants.AGENT_TYPE_L3,
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agents_db.Agent.host == host,
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agents_db.Agent.admin_state_up == sql.true())
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try:
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l3_agent = query.one()
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except (exc.MultipleResultsFound, exc.NoResultFound):
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LOG.debug(_('No enabled L3 agent on host %s'),
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host)
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return False
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if agents_db.AgentDbMixin.is_agent_down(
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l3_agent.heartbeat_timestamp):
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LOG.warn(_('L3 agent %s is not active'), l3_agent.id)
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# check if each of the specified routers is hosted
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if router_ids:
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routers = plugin.get_routers(
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context, filters={'id': router_ids})
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unscheduled_routers = []
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for router in routers:
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l3_agents = plugin.get_l3_agents_hosting_routers(
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context, [router['id']], admin_state_up=True)
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if l3_agents and not router.get('distributed', False):
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LOG.debug(_('Router %(router_id)s has already been'
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' hosted by L3 agent %(agent_id)s'),
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{'router_id': router['id'],
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'agent_id': l3_agents[0]['id']})
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else:
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unscheduled_routers.append(router)
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if not unscheduled_routers:
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# all (specified) routers are already scheduled
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return False
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else:
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# get all routers that are not hosted
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#TODO(gongysh) consider the disabled agent's router
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stmt = ~sql.exists().where(
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l3_db.Router.id ==
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l3_agentschedulers_db.RouterL3AgentBinding.router_id)
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unscheduled_router_ids = [router_id_[0] for router_id_ in
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context.session.query(
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l3_db.Router.id).filter(stmt)]
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if not unscheduled_router_ids:
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LOG.debug(_('No non-hosted routers'))
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return False
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unscheduled_routers = plugin.get_routers(
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context, filters={'id': unscheduled_router_ids})
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# check if the configuration of l3 agent is compatible
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# with the router
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to_removed_ids = set()
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for router in unscheduled_routers:
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candidates = plugin.get_l3_agent_candidates(context,
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router,
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[l3_agent])
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if not candidates:
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to_removed_ids.add(router['id'])
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target_routers = [r for r in unscheduled_routers
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if r['id'] not in to_removed_ids]
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if not target_routers:
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LOG.warn(_('No routers compatible with L3 agent configuration'
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' on host %s'), host)
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return False
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for router_dict in target_routers:
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if (router_dict.get('distributed', False)
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and self.dvr_has_binding(context,
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router_dict['id'],
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l3_agent.id)):
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continue
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self.bind_router(context, router_dict['id'], l3_agent)
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return True
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def get_candidates(self, plugin, context, sync_router, subnet_id):
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"""Return L3 agents where a router could be scheduled."""
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with context.session.begin(subtransactions=True):
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# allow one router is hosted by just
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# one enabled l3 agent hosting since active is just a
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# timing problem. Non-active l3 agent can return to
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# active any time
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l3_agents = plugin.get_l3_agents_hosting_routers(
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context, [sync_router['id']], admin_state_up=True)
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if l3_agents and not sync_router.get('distributed', False):
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LOG.debug(_('Router %(router_id)s has already been hosted'
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' by L3 agent %(agent_id)s'),
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{'router_id': sync_router['id'],
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'agent_id': l3_agents[0]['id']})
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return
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active_l3_agents = plugin.get_l3_agents(context, active=True)
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if not active_l3_agents:
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LOG.warn(_('No active L3 agents'))
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return
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new_l3agents = plugin.get_l3_agent_candidates(context,
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sync_router,
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active_l3_agents,
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subnet_id)
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old_l3agentset = set(l3_agents)
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if sync_router.get('distributed', False):
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new_l3agentset = set(new_l3agents)
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candidates = list(new_l3agentset - old_l3agentset)
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else:
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candidates = new_l3agents
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if not candidates:
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LOG.warn(_('No L3 agents can host the router %s'),
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sync_router['id'])
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return
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return candidates
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def bind_router(self, context, router_id, chosen_agent):
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"""Bind the router to the l3 agent which has been chosen."""
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try:
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with context.session.begin(subtransactions=True):
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binding = l3_agentschedulers_db.RouterL3AgentBinding()
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binding.l3_agent = chosen_agent
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binding.router_id = router_id
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context.session.add(binding)
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except db_exc.DBDuplicateEntry:
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LOG.debug('Router %(router_id)s has already been scheduled '
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'to L3 agent %(agent_id)s.',
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{'agent_id': chosen_agent.id,
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'router_id': router_id})
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return
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LOG.debug('Router %(router_id)s is scheduled to L3 agent '
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'%(agent_id)s', {'router_id': router_id,
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'agent_id': chosen_agent.id})
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def _schedule_router(self, plugin, context, router_id,
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candidates=None, hints=None):
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sync_router = plugin.get_router(context, router_id)
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subnet_id = hints.get('subnet_id') if hints else None
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if (hints and 'gw_exists' in hints
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and sync_router.get('distributed', False)):
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plugin.schedule_snat_router(
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context, router_id, sync_router, hints['gw_exists'])
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candidates = candidates or self.get_candidates(
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plugin, context, sync_router, subnet_id)
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if not candidates:
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return
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if sync_router.get('distributed', False):
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for chosen_agent in candidates:
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self.bind_router(context, router_id, chosen_agent)
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else:
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chosen_agent = self._choose_router_agent(
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plugin, context, candidates)
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self.bind_router(context, router_id, chosen_agent)
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return chosen_agent
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@abc.abstractmethod
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def _choose_router_agent(self, plugin, context, candidates):
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"""Choose an agent from candidates based on a specific policy."""
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pass
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class ChanceScheduler(L3Scheduler):
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"""Randomly allocate an L3 agent for a router."""
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def schedule(self, plugin, context, router_id,
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candidates=None, hints=None):
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return self._schedule_router(
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plugin, context, router_id, candidates=candidates, hints=hints)
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def _choose_router_agent(self, plugin, context, candidates):
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return random.choice(candidates)
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class LeastRoutersScheduler(L3Scheduler):
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"""Allocate to an L3 agent with the least number of routers bound."""
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def schedule(self, plugin, context, router_id,
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candidates=None, hints=None):
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return self._schedule_router(
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plugin, context, router_id, candidates=candidates, hints=hints)
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def _choose_router_agent(self, plugin, context, candidates):
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candidate_ids = [candidate['id'] for candidate in candidates]
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chosen_agent = plugin.get_l3_agent_with_min_routers(
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context, candidate_ids)
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return chosen_agent
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