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# Copyright 2017 Mirantis, Inc.
#
# 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 itertools
from oslo_log import log as logging
import tenacity
from tooz import coordination
LOG = logging.getLogger(__name__)
class PoolLock(object):
"""Tooz lock wrapper for pools of locks
If tooz coordinator is provided, it will attempt to grab any lock
from a predefined set of names, with configurable set size (lock pool),
and keep attempting for until given timeout is reached.
"""
def __init__(self, coordinator, locks_pool_size=1, locks_prefix='ngs-',
timeout=0):
self.coordinator = coordinator
self.locks_prefix = locks_prefix
self.lock_names = ("{}{}".format(locks_prefix, i)
for i in range(locks_pool_size))
self.locks_pool_size = locks_pool_size
self.timeout = timeout
def __enter__(self):
self.lock = False
if not self.coordinator:
return self
LOG.debug("Trying to acquire lock for %s", self.locks_prefix)
names = itertools.cycle(self.lock_names)
retry_kwargs = {'wait': tenacity.wait_random(min=0, max=1),
'reraise': True}
if self.timeout:
retry_kwargs['stop'] = tenacity.stop_after_delay(self.timeout)
@tenacity.retry(**retry_kwargs)
def grab_lock_from_pool():
name = next(names)
# NOTE(pas-ha) currently all tooz backends support locking API.
# In case this changes, this should be wrapped to not respin
# lock grabbing on NotImplemented exception.
lock = self.coordinator.get_lock(name.encode())
locked = lock.acquire(blocking=False)
if not locked:
raise coordination.LockAcquireFailed(
"Failed to acquire lock %s" % name)
return lock
try:
self.lock = grab_lock_from_pool()
except Exception:
msg = ("Failed to acquire any of %s locks for %s "
"for a netmiko action in %s seconds. "
"Try increasing acquire_timeout." % (
self.locks_pool_size, self.locks_prefix,
self.timeout))
LOG.error(msg, exc_info=True)
raise
return self
def __exit__(self, exc_type, exc_val, exc_tb):
if self.lock:
self.lock.release()
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