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# Copyright 2014-2015 Canonical Limited.
#
# This file is part of charm-helpers.
#
# charm-helpers is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License version 3 as
# published by the Free Software Foundation.
#
# charm-helpers is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with charm-helpers. If not, see <http://www.gnu.org/licenses/>.
'''
Functions for managing volumes in juju units. One volume is supported per unit.
Subordinates may have their own storage, provided it is on its own partition.
Configuration stanzas::
volume-ephemeral:
type: boolean
default: true
description: >
If false, a volume is mounted as sepecified in "volume-map"
If true, ephemeral storage will be used, meaning that log data
will only exist as long as the machine. YOU HAVE BEEN WARNED.
volume-map:
type: string
default: {}
description: >
YAML map of units to device names, e.g:
"{ rsyslog/0: /dev/vdb, rsyslog/1: /dev/vdb }"
Service units will raise a configure-error if volume-ephemeral
is 'true' and no volume-map value is set. Use 'juju set' to set a
value and 'juju resolved' to complete configuration.
Usage::
from charmsupport.volumes import configure_volume, VolumeConfigurationError
from charmsupport.hookenv import log, ERROR
def post_mount_hook():
stop_service('myservice')
def post_mount_hook():
start_service('myservice')
if __name__ == '__main__':
try:
configure_volume(before_change=pre_mount_hook,
after_change=post_mount_hook)
except VolumeConfigurationError:
log('Storage could not be configured', ERROR)
'''
# XXX: Known limitations
# - fstab is neither consulted nor updated
import os
from charmhelpers.core import hookenv
from charmhelpers.core import host
import yaml
MOUNT_BASE = '/srv/juju/volumes'
class VolumeConfigurationError(Exception):
'''Volume configuration data is missing or invalid'''
pass
def get_config():
'''Gather and sanity-check volume configuration data'''
volume_config = {}
config = hookenv.config()
errors = False
if config.get('volume-ephemeral') in (True, 'True', 'true', 'Yes', 'yes'):
volume_config['ephemeral'] = True
else:
volume_config['ephemeral'] = False
try:
volume_map = yaml.safe_load(config.get('volume-map', '{}'))
except yaml.YAMLError as e:
hookenv.log("Error parsing YAML volume-map: {}".format(e),
hookenv.ERROR)
errors = True
if volume_map is None:
# probably an empty string
volume_map = {}
elif not isinstance(volume_map, dict):
hookenv.log("Volume-map should be a dictionary, not {}".format(
type(volume_map)))
errors = True
volume_config['device'] = volume_map.get(os.environ['JUJU_UNIT_NAME'])
if volume_config['device'] and volume_config['ephemeral']:
# asked for ephemeral storage but also defined a volume ID
hookenv.log('A volume is defined for this unit, but ephemeral '
'storage was requested', hookenv.ERROR)
errors = True
elif not volume_config['device'] and not volume_config['ephemeral']:
# asked for permanent storage but did not define volume ID
hookenv.log('Ephemeral storage was requested, but there is no volume '
'defined for this unit.', hookenv.ERROR)
errors = True
unit_mount_name = hookenv.local_unit().replace('/', '-')
volume_config['mountpoint'] = os.path.join(MOUNT_BASE, unit_mount_name)
if errors:
return None
return volume_config
def mount_volume(config):
if os.path.exists(config['mountpoint']):
if not os.path.isdir(config['mountpoint']):
hookenv.log('Not a directory: {}'.format(config['mountpoint']))
raise VolumeConfigurationError()
else:
host.mkdir(config['mountpoint'])
if os.path.ismount(config['mountpoint']):
unmount_volume(config)
if not host.mount(config['device'], config['mountpoint'], persist=True):
raise VolumeConfigurationError()
def unmount_volume(config):
if os.path.ismount(config['mountpoint']):
if not host.umount(config['mountpoint'], persist=True):
raise VolumeConfigurationError()
def managed_mounts():
'''List of all mounted managed volumes'''
return filter(lambda mount: mount[0].startswith(MOUNT_BASE), host.mounts())
def configure_volume(before_change=lambda: None, after_change=lambda: None):
'''Set up storage (or don't) according to the charm's volume configuration.
Returns the mount point or "ephemeral". before_change and after_change
are optional functions to be called if the volume configuration changes.
'''
config = get_config()
if not config:
hookenv.log('Failed to read volume configuration', hookenv.CRITICAL)
raise VolumeConfigurationError()
if config['ephemeral']:
if os.path.ismount(config['mountpoint']):
before_change()
unmount_volume(config)
after_change()
return 'ephemeral'
else:
# persistent storage
if os.path.ismount(config['mountpoint']):
mounts = dict(managed_mounts())
if mounts.get(config['mountpoint']) != config['device']:
before_change()
unmount_volume(config)
mount_volume(config)
after_change()
else:
before_change()
mount_volume(config)
after_change()
return config['mountpoint']
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