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In the scenario of network interruption or connection manually shutdown, the service api can't be used any more, we should catch the exception. Change-Id: I276cdb70e35b14504c7139604066098703d9edec Closes-Bug: #1484804
210 lines
5.9 KiB
Python
210 lines
5.9 KiB
Python
# Copyright 2015 Huawei Technologies Co., Ltd.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain 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,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import six
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from oslo_concurrency import lockutils
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from oslo_config import cfg
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from oslo_log import log
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from oslo_service import threadgroup
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from retrying import retry
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import tooz.coordination
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from mistral import utils
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LOG = log.getLogger(__name__)
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_SERVICE_COORDINATOR = None
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class ServiceCoordinator(object):
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"""Service coordinator.
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This class uses the `tooz` library to manage group membership.
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To ensure that the other agents know this agent is still alive,
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the `heartbeat` method should be called periodically.
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"""
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def __init__(self, my_id=None):
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self._coordinator = None
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self._my_id = my_id or utils.get_process_identifier()
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self._started = False
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def start(self):
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backend_url = cfg.CONF.coordination.backend_url
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if backend_url:
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try:
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self._coordinator = tooz.coordination.get_coordinator(
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backend_url,
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self._my_id
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)
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self._coordinator.start()
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self._started = True
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LOG.info('Coordination backend started successfully.')
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except tooz.coordination.ToozError as e:
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self._started = False
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LOG.exception('Error connecting to coordination backend. '
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'%s', six.text_type(e))
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def stop(self):
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if not self.is_active():
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return
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try:
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self._coordinator.stop()
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except tooz.coordination.ToozError:
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LOG.warning('Error connecting to coordination backend.')
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finally:
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self._coordinator = None
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self._started = False
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def is_active(self):
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return self._coordinator and self._started
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def heartbeat(self):
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if not self.is_active():
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# Re-connect.
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self.start()
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if not self.is_active():
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LOG.debug("Coordination backend didn't start.")
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return
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try:
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self._coordinator.heartbeat()
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except tooz.coordination.ToozError as e:
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LOG.exception('Error sending a heartbeat to coordination '
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'backend. %s', six.text_type(e))
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self._started = False
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@retry(stop_max_attempt_number=5)
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def join_group(self, group_id):
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if not self.is_active() or not group_id:
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return
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try:
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join_req = self._coordinator.join_group(group_id)
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join_req.get()
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LOG.info(
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'Joined service group:%s, member:%s',
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group_id,
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self._my_id
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)
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return
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except tooz.coordination.MemberAlreadyExist:
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return
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except tooz.coordination.GroupNotCreated as e:
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create_grp_req = self._coordinator.create_group(group_id)
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try:
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create_grp_req.get()
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except tooz.coordination.GroupAlreadyExist:
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pass
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# Re-raise exception to join group again.
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raise e
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def leave_group(self, group_id):
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if self.is_active():
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self._coordinator.leave_group(group_id)
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LOG.info(
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'Left service group:%s, member:%s',
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group_id,
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self._my_id
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)
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def get_members(self, group_id):
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"""Gets members of coordination group.
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ToozError exception must be handled when this function is invoded, we
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leave it to the invoker for the handling decision.
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"""
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if not self.is_active():
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return []
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get_members_req = self._coordinator.get_members(group_id)
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try:
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members = get_members_req.get()
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LOG.debug('Members of group %s: %s', group_id, members)
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return members
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except tooz.coordination.GroupNotCreated:
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LOG.warning('Group %s does not exist.', group_id)
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return []
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def cleanup_service_coordinator():
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"""Intends to be used by tests to recreate service coordinator."""
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global _SERVICE_COORDINATOR
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_SERVICE_COORDINATOR = None
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def get_service_coordinator(my_id=None):
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global _SERVICE_COORDINATOR
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if not _SERVICE_COORDINATOR:
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_SERVICE_COORDINATOR = ServiceCoordinator(my_id=my_id)
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_SERVICE_COORDINATOR.start()
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return _SERVICE_COORDINATOR
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class Service(object):
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def __init__(self, group_type):
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self.group_type = group_type
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self._tg = None
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@lockutils.synchronized('service_coordinator')
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def register_membership(self):
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"""Registers group membership.
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Because this method will be invoked on each service startup almost at
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the same time, so it must be synchronized, in case all the services
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are started within same process.
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"""
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service_coordinator = get_service_coordinator()
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if service_coordinator.is_active():
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service_coordinator.join_group(self.group_type)
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self._tg = threadgroup.ThreadGroup()
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self._tg.add_timer(
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cfg.CONF.coordination.heartbeat_interval,
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service_coordinator.heartbeat
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)
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def stop(self):
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service_coordinator = get_service_coordinator()
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if service_coordinator.is_active():
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self._tg.stop()
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service_coordinator.stop()
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