deb-manila/manila/coordination.py
Tom Barron 326755f42c coordination: use tooz builtin heartbeat feature
Since a few versions, tooz can manage the heartbeat entirely
internally.

Use that feature and simplify the manila code.

See Cinder change [1].

Closes-Bug: #1691323

[1] I7fa654caf6620d410d4e297d3d8af2215e27ed12

Change-Id: I86ef7a092a3ab7fd0a90ab664b7f9f62a275901b
2017-05-17 10:38:53 +02:00

228 lines
7.8 KiB
Python

# 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.
"""Tooz Coordination and locking utilities."""
import inspect
import decorator
from oslo_config import cfg
from oslo_log import log
from oslo_utils import uuidutils
import six
from tooz import coordination
from tooz import locking
from manila import exception
from manila.i18n import _
LOG = log.getLogger(__name__)
coordination_opts = [
cfg.StrOpt('backend_url',
default='file://$state_path',
help='The back end URL to use for distributed coordination.'),
cfg.FloatOpt('heartbeat',
default=1.0,
help='Number of seconds between heartbeats for distributed '
'coordination. No longer used since distributed '
'coordination manages its heartbeat internally.',
deprecated_for_removal=True,
deprecated_reason='This option is no longer used.',
deprecated_since='16.0.0'),
cfg.FloatOpt('initial_reconnect_backoff',
default=0.1,
help='Initial number of seconds to wait after failed '
'reconnection. No longer used since distributed '
'coordination manages its heartbeat internally.',
deprecated_for_removal=True,
deprecated_reason='This option is no longer used.',
deprecated_since='16.0.0'),
cfg.FloatOpt('max_reconnect_backoff',
default=60.0,
help='Maximum number of seconds between sequential '
'reconnection retries. No longer used since '
'distributed coordination manages its heartbeat '
'internally.',
deprecated_for_removal=True,
deprecated_reason='This option is no longer used.',
deprecated_since='16.0.0'),
]
CONF = cfg.CONF
CONF.register_opts(coordination_opts, group='coordination')
class Coordinator(object):
"""Tooz coordination wrapper.
Coordination member id is created from concatenated `prefix` and
`agent_id` parameters.
:param str agent_id: Agent identifier
:param str prefix: Used to provide member identifier with a
meaningful prefix.
"""
def __init__(self, agent_id=None, prefix=''):
self.coordinator = None
self.agent_id = agent_id or uuidutils.generate_uuid()
self.started = False
self.prefix = prefix
def start(self):
"""Connect to coordination back end."""
if self.started:
return
# NOTE(gouthamr): Tooz expects member_id as a byte string.
member_id = (self.prefix + self.agent_id).encode('ascii')
self.coordinator = coordination.get_coordinator(
cfg.CONF.coordination.backend_url, member_id)
self.coordinator.start(start_heart=True)
self.started = True
def stop(self):
"""Disconnect from coordination back end."""
msg = 'Stopped Coordinator (Agent ID: %(agent)s, prefix: %(prefix)s)'
msg_args = {'agent': self.agent_id, 'prefix': self.prefix}
if self.started:
self.coordinator.stop()
self.coordinator = None
self.started = False
LOG.info(msg, msg_args)
def get_lock(self, name):
"""Return a Tooz back end lock.
:param str name: The lock name that is used to identify it
across all nodes.
"""
# NOTE(gouthamr): Tooz expects lock name as a byte string
lock_name = (self.prefix + name).encode('ascii')
if self.started:
return self.coordinator.get_lock(lock_name)
else:
raise exception.LockCreationFailed(_('Coordinator uninitialized.'))
LOCK_COORDINATOR = Coordinator(prefix='manila-')
class Lock(locking.Lock):
"""Lock with dynamic name.
:param str lock_name: Lock name.
:param dict lock_data: Data for lock name formatting.
:param coordinator: Coordinator object to use when creating lock.
Defaults to the global coordinator.
Using it like so::
with Lock('mylock'):
...
ensures that only one process at a time will execute code in context.
Lock name can be formatted using Python format string syntax::
Lock('foo-{share.id}, {'share': ...,}')
Available field names are keys of lock_data.
"""
def __init__(self, lock_name, lock_data=None, coordinator=None):
super(Lock, self).__init__(six.text_type(id(self)))
lock_data = lock_data or {}
self.coordinator = coordinator or LOCK_COORDINATOR
self.blocking = True
self.lock = self._prepare_lock(lock_name, lock_data)
def _prepare_lock(self, lock_name, lock_data):
if not isinstance(lock_name, six.string_types):
raise ValueError(_('Not a valid string: %s') % lock_name)
return self.coordinator.get_lock(lock_name.format(**lock_data))
def acquire(self, blocking=None):
"""Attempts to acquire lock.
:param blocking: If True, blocks until the lock is acquired. If False,
returns right away. Otherwise, the value is used as a timeout
value and the call returns maximum after this number of seconds.
:return: returns true if acquired (false if not)
:rtype: bool
"""
blocking = self.blocking if blocking is None else blocking
return self.lock.acquire(blocking=blocking)
def release(self):
"""Attempts to release lock.
The behavior of releasing a lock which was not acquired in the first
place is undefined.
"""
self.lock.release()
def synchronized(lock_name, blocking=True, coordinator=None):
"""Synchronization decorator.
:param str lock_name: Lock name.
:param blocking: If True, blocks until the lock is acquired.
If False, raises exception when not acquired. Otherwise,
the value is used as a timeout value and if lock is not acquired
after this number of seconds exception is raised.
:param coordinator: Coordinator object to use when creating lock.
Defaults to the global coordinator.
:raises tooz.coordination.LockAcquireFailed: if lock is not acquired
Decorating a method like so::
@synchronized('mylock')
def foo(self, *args):
...
ensures that only one process will execute the foo method at a time.
Different methods can share the same lock::
@synchronized('mylock')
def foo(self, *args):
...
@synchronized('mylock')
def bar(self, *args):
...
This way only one of either foo or bar can be executing at a time.
Lock name can be formatted using Python format string syntax::
@synchronized('{f_name}-{shr.id}-{snap[name]}')
def foo(self, shr, snap):
...
Available field names are: decorated function parameters and
`f_name` as a decorated function name.
"""
@decorator.decorator
def _synchronized(f, *a, **k):
call_args = inspect.getcallargs(f, *a, **k)
call_args['f_name'] = f.__name__
lock = Lock(lock_name, call_args, coordinator)
with lock(blocking):
LOG.debug('Lock "%(name)s" acquired by "%(function)s".',
{'name': lock_name, 'function': f.__name__})
return f(*a, **k)
return _synchronized