# 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 os
import socket
import threading
from oslo_concurrency import processutils
from oslo_config import cfg
from glance_store import exceptions
from glance_store.i18n import _LE, _LW
LOG = logging.getLogger(__name__)
HOST = socket.gethostname()
CONF = cfg.CONF
class HostMountStateManagerMeta(type):
_instance = {}
def __call__(cls, *args, **kwargs):
if cls not in cls._instance:
cls._instance[cls] = super(
HostMountStateManagerMeta, cls).__call__(*args, **kwargs)
return cls._instance[cls]
class _HostMountStateManager(metaclass=HostMountStateManagerMeta):
"""A global manager of filesystem mounts.
_HostMountStateManager manages a _HostMountState object for the current
glance node. Primarily it creates one on object initialization and returns
it via get_state().
_HostMountStateManager manages concurrency itself. Independent callers do
not need to consider interactions between multiple _HostMountStateManager
calls when designing their own locking.
"""
# Reset state of global _HostMountStateManager
state = None
use_count = 0
# Guards both state and use_count
cond = threading.Condition()
def __init__(self, host):
"""Initialise a new _HostMountState
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 _HostMountState initialisation
# and an on-going mount/unmount 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 _HostMountState')
self.state = _HostMountState()
backends = []
enabled_backends = CONF.enabled_backends
if enabled_backends:
for backend in enabled_backends:
if enabled_backends[backend] == 'cinder':
backends.append(backend)
else:
backends.append('glance_store')
for backend in backends:
mountpoint = getattr(CONF, backend).cinder_mount_point_base
# This is currently designed for cinder nfs backend only.
# Later can be modified to work with other *fs backends.
mountpoint = os.path.join(mountpoint, 'nfs')
# There will probably be the same rootwrap file for all stores,
# generalizing this will be done in a later refactoring
rootwrap = getattr(CONF, backend).rootwrap_config
rootwrap = ('sudo glance-rootwrap %s' % rootwrap)
dirs = []
# fetch the directories in the mountpoint path
if os.path.isdir(mountpoint):
dirs = os.listdir(mountpoint)
else:
continue
if not dirs:
return
for dir in dirs:
# for every directory in the mountpath, we
# unmount it (if mounted) and remove it
dir = os.path.join(mountpoint, dir)
with self.get_state() as mount_state:
if os.path.exists(dir) and not os.path.ismount(dir):
try:
os.rmdir(dir)
except Exception as ex:
LOG.debug(
"Couldn't remove directory"
"%(mountpoint)s: %(reason)s",
{'mountpoint': mountpoint,
'reason': ex})
else:
mount_state.umount(None, dir, HOST, rootwrap)
@contextlib.contextmanager
def get_state(self):
"""Return the current mount state.
_HostMountStateManager will not permit a new state object to be
created while any previous state object is still in use.
:rtype: _HostMountState
"""
# We hold the instance lock here so that if a _HostMountState 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 _HostMountState')
yield state
finally:
with self.cond:
self.use_count -= 1
self.cond.notify_all()
class _HostMountState(object):
"""A data structure recording all managed mountpoints and the
attachments in use for each one. _HostMountState ensures that the glance
node only attempts to mount a single mountpoint in use by multiple
attachments once, and that it is not unmounted until it is no longer in use
by any attachments.
Callers should not create a _HostMountState directly, but should obtain
it via:
with mount.get_manager().get_state() as state:
state.mount(...)
_HostMountState manages concurrency itself. Independent callers do not need
to consider interactions between multiple _HostMountState calls when
designing their own locking.
"""
class _MountPoint(object):
"""A single mountpoint, and the set of attachments in use on it."""
def __init__(self):
# A guard for operations on this mountpoint
# N.B. Care is required using this lock, as it will be deleted
# if the containing _MountPoint is deleted.
self.lock = threading.Lock()
# The set of attachments on this mountpoint.
self.attachments = set()
def add_attachment(self, vol_name, host):
self.attachments.add((vol_name, host))
def remove_attachment(self, vol_name, host):
self.attachments.remove((vol_name, host))
def in_use(self):
return len(self.attachments) > 0
def __init__(self):
"""Initialise _HostMountState"""
self.mountpoints = collections.defaultdict(self._MountPoint)
@contextlib.contextmanager
def _get_locked(self, mountpoint):
"""Get a locked mountpoint object
:param mountpoint: The path of the mountpoint whose object we should
return.
:rtype: _HostMountState._MountPoint
"""
while True:
mount = self.mountpoints[mountpoint]
with mount.lock:
if self.mountpoints[mountpoint] is mount:
yield mount
break
def mount(self, fstype, export, vol_name, mountpoint, host,
rootwrap_helper, options):
"""Ensure a mountpoint is available for an attachment, mounting it
if necessary.
If this is the first attachment on this mountpoint, we will mount it
with:
mount -t <fstype> <options> <export> <mountpoint>
:param fstype: The filesystem type to be passed to mount command.
:param export: The type-specific identifier of the filesystem to be
mounted. e.g. for nfs 'host.example.com:/mountpoint'.
:param vol_name: The name of the volume on the remote filesystem.
:param mountpoint: The directory where the filesystem will be
mounted on the local compute host.
:param host: The host the volume will be attached to.
:param options: An arbitrary list of additional arguments to be
passed to the mount command immediate before export
and mountpoint.
"""
LOG.debug('_HostMountState.mount(fstype=%(fstype)s, '
'export=%(export)s, vol_name=%(vol_name)s, %(mountpoint)s, '
'options=%(options)s)',
{'fstype': fstype, 'export': export, 'vol_name': vol_name,
'mountpoint': mountpoint, 'options': options})
with self._get_locked(mountpoint) as mount:
if not os.path.ismount(mountpoint):
LOG.debug('Mounting %(mountpoint)s',
{'mountpoint': mountpoint})
os.makedirs(mountpoint)
mount_cmd = ['mount', '-t', fstype]
if options is not None:
mount_cmd.extend(options)
mount_cmd.extend([export, mountpoint])
try:
processutils.execute(*mount_cmd, run_as_root=True,
root_helper=rootwrap_helper)
except Exception:
# Check to see if mountpoint is mounted despite the error
# eg it was already mounted
if os.path.ismount(mountpoint):
# We're not going to raise the exception because we're
# in the desired state anyway. However, this is still
# unusual so we'll log it.
LOG.exception(_LE('Error mounting %(fstype)s export '
'%(export)s on %(mountpoint)s. '
'Continuing because mountpount is '
'mounted despite this.'),
{'fstype': fstype, 'export': export,
'mountpoint': mountpoint})
else:
# If the mount failed there's no reason for us to keep
# a record of it. It will be created again if the
# caller retries.
# Delete while holding lock
del self.mountpoints[mountpoint]
raise
mount.add_attachment(vol_name, host)
LOG.debug('_HostMountState.mount() for %(mountpoint)s '
'completed successfully',
{'mountpoint': mountpoint})
def umount(self, vol_name, mountpoint, host, rootwrap_helper):
"""Mark an attachment as no longer in use, and unmount its mountpoint
if necessary.
:param vol_name: The name of the volume on the remote filesystem.
:param mountpoint: The directory where the filesystem is be
mounted on the local compute host.
:param host: The host the volume was attached to.
"""
LOG.debug('_HostMountState.umount(vol_name=%(vol_name)s, '
'mountpoint=%(mountpoint)s)',
{'vol_name': vol_name, 'mountpoint': mountpoint})
with self._get_locked(mountpoint) as mount:
try:
mount.remove_attachment(vol_name, host)
except KeyError:
LOG.warning(_LW("Request to remove attachment "
"(%(vol_name)s, %(host)s) from "
"%(mountpoint)s, but we don't think it's in "
"use."),
{'vol_name': vol_name, 'host': host,
'mountpoint': mountpoint})
if not mount.in_use():
mounted = os.path.ismount(mountpoint)
if mounted:
mounted = self._real_umount(mountpoint, rootwrap_helper)
# Delete our record entirely if it's unmounted
if not mounted:
del self.mountpoints[mountpoint]
LOG.debug('_HostMountState.umount() for %(mountpoint)s '
'completed successfully',
{'mountpoint': mountpoint})
def _real_umount(self, mountpoint, rootwrap_helper):
# Unmount and delete a mountpoint.
# Return mount state after umount (i.e. True means still mounted)
LOG.debug('Unmounting %(mountpoint)s', {'mountpoint': mountpoint})
try:
processutils.execute('umount', mountpoint, run_as_root=True,
attempts=3, delay_on_retry=True,
root_helper=rootwrap_helper)
except processutils.ProcessExecutionError as ex:
LOG.error(_LE("Couldn't unmount %(mountpoint)s: %(reason)s"),
{'mountpoint': mountpoint, 'reason': ex})
if not os.path.ismount(mountpoint):
try:
os.rmdir(mountpoint)
except Exception as ex:
LOG.error(_LE("Couldn't remove directory %(mountpoint)s: "
"%(reason)s"),
{'mountpoint': mountpoint,
'reason': ex})
return False
return True
__manager__ = _HostMountStateManager(HOST)
def mount(fstype, export, vol_name, mountpoint, host, rootwrap_helper,
options=None):
"""A convenience wrapper around _HostMountState.mount()"""
with __manager__.get_state() as mount_state:
mount_state.mount(fstype, export, vol_name, mountpoint, host,
rootwrap_helper, options)
def umount(vol_name, mountpoint, host, rootwrap_helper):
"""A convenience wrapper around _HostMountState.umount()"""
with __manager__.get_state() as mount_state:
mount_state.umount(vol_name, mountpoint, host, rootwrap_helper)
