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deps/layer/layer-leadership/reactive/leadership.py

 

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# Copyright 2015-2016 Canonical Ltd.

 

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#

 

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# This file is part of the Leadership Layer for Juju.

 

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#

 

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# This program is free software: you can redistribute it and/or modify

 

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# it under the terms of the GNU General Public License version 3, as

 

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# published by the Free Software Foundation.

 

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#

 

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# This program is distributed in the hope that it will be useful, but

 

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# WITHOUT ANY WARRANTY; without even the implied warranties of

 

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# MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR

 

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# PURPOSE.  See the GNU General Public License for more details.

 

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#

 

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# You should have received a copy of the GNU General Public License

 

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# along with this program.  If not, see <http://www.gnu.org/licenses/>.

 

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from charmhelpers.core import hookenv

 

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from charmhelpers.core import unitdata

 

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from charms import reactive

 

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from charms.leadership import leader_get, leader_set

 

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__all__ = ['leader_get', 'leader_set']  # Backwards compatibility

 

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def initialize_leadership_state():

 

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    '''Initialize leadership.* states from the hook environment.

 

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    Invoked by hookenv.atstart() so states are available in

 

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    @hook decorated handlers.

 

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    '''

 

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    is_leader = hookenv.is_leader()

 

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    if is_leader:

 

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        hookenv.log('Initializing Leadership Layer (is leader)')

 

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    else:

 

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        hookenv.log('Initializing Leadership Layer (is follower)')

 

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    reactive.helpers.toggle_state('leadership.is_leader', is_leader)

 

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    previous = unitdata.kv().getrange('leadership.settings.', strip=True)

 

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    current = hookenv.leader_get()

 

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    # Handle deletions.

 

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    for key in set(previous.keys()) - set(current.keys()):

 

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        current[key] = None

 

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    any_changed = False

 

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    for key, value in current.items():

 

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        reactive.helpers.toggle_state('leadership.changed.{}'.format(key),

 

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                                      value != previous.get(key))

 

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        if value != previous.get(key):

 

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            any_changed = True

 

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        reactive.helpers.toggle_state('leadership.set.{}'.format(key),

 

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                                      value is not None)

 

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    reactive.helpers.toggle_state('leadership.changed', any_changed)

 

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    unitdata.kv().update(current, prefix='leadership.settings.')

 

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# Per https://github.com/juju-solutions/charms.reactive/issues/33,

 

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# this module may be imported multiple times so ensure the

 

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# initialization hook is only registered once. I have to piggy back

 

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# onto the namespace of a module imported before reactive discovery

 

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# to do this.

 

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if not hasattr(reactive, '_leadership_registered'):

 

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    hookenv.atstart(initialize_leadership_state)

 

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    reactive._leadership_registered = True

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