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Diffstat (limited to 'charms/trusty/cassandra/hooks/charmhelpers/contrib/charmsupport/volumes.py')
| -rw-r--r-- | charms/trusty/cassandra/hooks/charmhelpers/contrib/charmsupport/volumes.py | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/charms/trusty/cassandra/hooks/charmhelpers/contrib/charmsupport/volumes.py b/charms/trusty/cassandra/hooks/charmhelpers/contrib/charmsupport/volumes.py new file mode 100644 index 0000000..320961b --- /dev/null +++ b/charms/trusty/cassandra/hooks/charmhelpers/contrib/charmsupport/volumes.py @@ -0,0 +1,175 @@ +# 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'] |