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