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# Copyright 2021 RedHat Inc.
# All Rights Reserved.
#
# 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 collections
import contextlib
import logging
import socket
import threading
from oslo_config import cfg
from glance_store.common import cinder_utils
from glance_store import exceptions
from glance_store.i18n import _LE, _LW
LOG = logging.getLogger(__name__)
HOST = socket.gethostname()
CONF = cfg.CONF
class AttachmentStateManagerMeta(type):
_instance = {}
def __call__(cls, *args, **kwargs):
if cls not in cls._instance:
cls._instance[cls] = super(
AttachmentStateManagerMeta, cls).__call__(*args, **kwargs)
return cls._instance[cls]
class _AttachmentStateManager(metaclass=AttachmentStateManagerMeta):
"""A global manager of a volume's multiple attachments.
_AttachmentStateManager manages a _AttachmentState object for the current
glance node. Primarily it creates one on object initialization and returns
it via get_state().
_AttachmentStateManager manages concurrency itself. Independent callers do
not need to consider interactions between multiple _AttachmentStateManager
calls when designing their own locking.
"""
# Reset state of global _AttachmentStateManager
state = None
use_count = 0
# Guards both state and use_count
cond = threading.Condition()
def __init__(self, host):
"""Initialise a new _AttachmentState
We will block before creating a new state until all operations
using a previous state have completed.
:param host: host
"""
# Wait until all operations using a previous state are
# complete before initialising a new one. Note that self.state is
# already None, set either by initialisation or by host_down. This
# means the current state will not be returned to any new callers,
# and use_count will eventually reach zero.
# We do this to avoid a race between _AttachmentState initialisation
# and an on-going attach/detach operation
self.host = host
while self.use_count != 0:
self.cond.wait()
# Another thread might have initialised state while we were
# waiting
if self.state is None:
LOG.debug('Initialising _AttachmentStateManager')
self.state = _AttachmentState()
@contextlib.contextmanager
def get_state(self):
"""Return the current attachment state.
_AttachmentStateManager will not permit a new state object to be
created while any previous state object is still in use.
:rtype: _AttachmentState
"""
# We hold the instance lock here so that if a _AttachmentState is
# currently initialising we'll wait for it to complete rather than
# fail.
with self.cond:
state = self.state
if state is None:
LOG.error('Host not initialized')
raise exceptions.HostNotInitialized(host=self.host)
self.use_count += 1
try:
LOG.debug('Got _AttachmentState')
yield state
finally:
with self.cond:
self.use_count -= 1
self.cond.notify_all()
class _AttachmentState(object):
"""A data structure recording all managed attachments. _AttachmentState
ensures that the glance node only attempts to a single multiattach volume
in use by multiple attachments once, and that it is not disconnected until
it is no longer in use by any attachments.
Callers should not create a _AttachmentState directly, but should obtain
it via:
with attachment.get_manager().get_state() as state:
state.attach(...)
_AttachmentState manages concurrency itself. Independent callers do not
need to consider interactions between multiple _AttachmentState calls when
designing their own locking.
"""
class _Attachment(object):
# A single multiattach volume, and the set of attachments in use
# on it.
def __init__(self):
# A guard for operations on this volume
self.lock = threading.Lock()
# The set of attachments on this volume
self.attachments = set()
def add_attachment(self, attachment_id, host):
self.attachments.add((attachment_id, host))
def remove_attachment(self, attachment_id, host):
self.attachments.remove((attachment_id, host))
def in_use(self):
return len(self.attachments) > 0
def __init__(self):
"""Initialise _AttachmentState"""
self.volumes = collections.defaultdict(self._Attachment)
self.volume_api = cinder_utils.API()
@contextlib.contextmanager
def _get_locked(self, volume):
"""Get a locked attachment object
:param mountpoint: The path of the volume whose attachment we should
return.
:rtype: _AttachmentState._Attachment
"""
while True:
vol = self.volumes[volume]
with vol.lock:
if self.volumes[volume] is vol:
yield vol
break
def attach(self, client, volume_id, host, mode=None):
"""Ensure a volume is available for an attachment and create an
attachment
:param client: Cinderclient object
:param volume_id: ID of the volume to attach
:param host: The host the volume will be attached to
:param mode: The attachment mode
"""
LOG.debug('_AttachmentState.attach(volume_id=%(volume_id)s, '
'host=%(host)s, mode=%(mode)s)',
{'volume_id': volume_id, 'host': host, 'mode': mode})
with self._get_locked(volume_id) as vol_attachment:
try:
attachment = self.volume_api.attachment_create(
client, volume_id, mode=mode)
except Exception:
LOG.exception(_LE('Error attaching volume %(volume_id)s',
{'volume_id': volume_id}))
del self.volumes[volume_id]
raise
vol_attachment.add_attachment(attachment['id'], host)
LOG.debug('_AttachmentState.attach for volume_id=%(volume_id)s '
'and attachment_id=%(attachment_id)s completed successfully',
{'volume_id': volume_id, 'attachment_id': attachment['id']})
return attachment
def detach(self, client, attachment_id, volume_id, host, conn,
connection_info, device):
"""Delete the attachment no longer in use, and disconnect volume
if necessary.
:param client: Cinderclient object
:param attachment_id: ID of the attachment between volume and host
:param volume_id: ID of the volume to attach
:param host: The host the volume was attached to
:param conn: connector object
:param connection_info: connection information of the volume we are
detaching
:device: device used to write image
"""
LOG.debug('_AttachmentState.detach(vol_id=%(volume_id)s, '
'attachment_id=%(attachment_id)s)',
{'volume_id': volume_id, 'attachment_id': attachment_id})
with self._get_locked(volume_id) as vol_attachment:
try:
vol_attachment.remove_attachment(attachment_id, host)
except KeyError:
LOG.warning(_LW("Request to remove attachment "
"(%(volume_id)s, %(host)s) but we "
"don't think it's in use."),
{'volume_id': volume_id, 'host': host})
if not vol_attachment.in_use():
conn.disconnect_volume(connection_info, device)
del self.volumes[volume_id]
self.volume_api.attachment_delete(client, attachment_id)
LOG.debug('_AttachmentState.detach for volume %(volume_id)s '
'and attachment_id=%(attachment_id)s completed '
'successfully',
{'volume_id': volume_id,
'attachment_id': attachment_id})
__manager__ = _AttachmentStateManager(HOST)
def attach(client, volume_id, host, mode=None):
"""A convenience wrapper around _AttachmentState.attach()"""
with __manager__.get_state() as attach_state:
attachment = attach_state.attach(client, volume_id, host, mode=mode)
return attachment
def detach(client, attachment_id, volume_id, host, conn, connection_info,
device):
"""A convenience wrapper around _AttachmentState.detach()"""
with __manager__.get_state() as attach_state:
attach_state.detach(client, attachment_id, volume_id, host, conn,
connection_info, device)
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