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#
# Copyright 2014 Red Hat, Inc.
# Copyright 2015 Hewlett-Packard Development Company, L.P.
#
# Author: Endre Karlson <endre.karlson@hpe.com>
#
# 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 math
import time
from oslo_log import log
import tenacity
import tooz.coordination
import designate.conf
from designate.utils import generate_uuid
CONF = designate.conf.CONF
LOG = log.getLogger(__name__)
def _retry_if_tooz_error(exception):
"""Return True if we should retry, False otherwise"""
return isinstance(exception, tooz.coordination.ToozError)
class Coordination(object):
def __init__(self, name, tg):
self.name = name
self.tg = tg
self.coordination_id = None
self._coordinator = None
self._started = False
@property
def coordinator(self):
return self._coordinator
@property
def started(self):
return self._started
def start(self):
self.coordination_id = ":".join([CONF.host, generate_uuid()])
if CONF.coordination.backend_url is not None:
backend_url = CONF.coordination.backend_url
self._coordinator = tooz.coordination.get_coordinator(
backend_url, self.coordination_id.encode())
self._started = False
self.tg.add_timer(CONF.coordination.heartbeat_interval,
self._coordinator_heartbeat)
self.tg.add_timer(CONF.coordination.run_watchers_interval,
self._coordinator_run_watchers)
else:
LOG.warning('No coordination backend configured, distributed '
'coordination functionality will be disabled. '
'Please configure a coordination backend.')
if self._coordinator is not None:
while not self._started:
try:
self._coordinator.start()
try:
create_group_req = self._coordinator.create_group(
self.name)
create_group_req.get()
except tooz.coordination.GroupAlreadyExist:
pass
join_group_req = self._coordinator.join_group(self.name)
join_group_req.get()
self._started = True
except Exception:
LOG.warning('Failed to start Coordinator', exc_info=True)
time.sleep(15)
def stop(self):
if self._coordinator is not None:
self._started = False
leave_group_req = self._coordinator.leave_group(self.name)
leave_group_req.get()
self._coordinator.stop()
self._coordinator = None
def _coordinator_heartbeat(self):
if not self._started:
return
try:
self._coordinator.heartbeat()
except tooz.coordination.ToozError:
LOG.warning('Error sending a heartbeat to coordination backend.')
def _coordinator_run_watchers(self):
if not self._started:
return
self._coordinator.run_watchers()
class Partitioner(object):
def __init__(self, coordinator, group_id, my_id, partitions):
self._coordinator = coordinator
self._group_id = group_id
self._my_id = my_id
self._partitions = partitions
self._started = False
self._my_partitions = None
self._callbacks = []
def _warn_no_backend(self):
LOG.warning('No coordination backend configured, assuming we are '
'the only worker. Please configure a coordination '
'backend')
@tenacity.retry(stop=tenacity.stop_after_attempt(5),
wait=tenacity.wait_random(max=2),
retry=tenacity.retry_if_exception(_retry_if_tooz_error),
reraise=True)
def _get_members(self, group_id):
get_members_req = self._coordinator.get_members(group_id)
try:
return get_members_req.get()
except tooz.coordination.GroupNotCreated:
LOG.error('Attempting to partition over a non-existent group: %s',
self._group_id)
raise
except tooz.coordination.ToozError:
LOG.error('Error getting group membership info from coordination '
'backend.')
raise
def _on_group_change(self, event):
LOG.debug('Received member change %s', event)
members, self._my_partitions = self._update_partitions()
self._run_callbacks(members, event)
def _partition(self, members, me, partitions):
member_count = len(members)
partition_count = len(partitions)
partition_size = int(
math.ceil(float(partition_count) / float(member_count)))
my_index = members.index(me)
my_start = partition_size * my_index
my_end = my_start + partition_size
return partitions[my_start:my_end]
def _run_callbacks(self, members, event):
for cb in self._callbacks:
cb(self.my_partitions, members, event)
def _update_partitions(self):
# Recalculate partitions - we need to sort the list of members
# alphabetically so that it's the same order across all nodes.
members = sorted(list(self._get_members(self._group_id)))
partitions = self._partition(
members, self._my_id, self._partitions)
return members, partitions
@property
def my_partitions(self):
return self._my_partitions
def start(self):
"""Allow the partitioner to start timers after the coordinator has
gotten it's connections up.
"""
LOG.debug('Starting partitioner')
if self._coordinator:
self._coordinator.watch_join_group(
self._group_id, self._on_group_change)
self._coordinator.watch_leave_group(
self._group_id, self._on_group_change)
# We need to get our partitions now. Events doesn't help in this
# case since they require state change in the group that we wont
# get when starting initially
self._my_partitions = self._update_partitions()[1]
else:
self._my_partitions = self._partitions
self._run_callbacks(None, None)
self._started = True
def watch_partition_change(self, callback):
LOG.debug('Watching for change %s', self._group_id)
self._callbacks.append(callback)
if self._started:
if not self._coordinator:
self._warn_no_backend()
callback(self._my_partitions, None, None)
def unwatch_partition_change(self, callback):
self._callbacks.remove(callback)
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