def is_elected_leader(resource):
"""
Returns True if the charm executing this is the elected cluster leader.
It relies on two mechanisms to determine leadership:
1. If juju is sufficiently new and leadership election is supported,
the is_leader command will be used.
2. If the charm is part of a corosync cluster, call corosync to
determine leadership.
3. If the charm is not part of a corosync cluster, the leader is
determined as being "the alive unit with the lowest unit numer". In
other words, the oldest surviving unit.
"""
try:
return juju_is_leader()
except NotImplementedError:
log(
'Juju leadership election feature not enabled'
', using fallback support',
level=WARNING)
if is_clustered():
if not is_crm_leader(resource):
log('Deferring action to CRM leader.', level=INFO)
return False
else:
peers = peer_units()
if peers and not oldest_peer(peers):
log('Deferring action to oldest service unit.', level=INFO)
return False
return True
def is_elected_leader(resource):
"""
Returns True if the charm executing this is the elected cluster leader.
It relies on two mechanisms to determine leadership:
1. If juju is sufficiently new and leadership election is supported,
the is_leader command will be used.
2. If the charm is part of a corosync cluster, call corosync to
determine leadership.
3. If the charm is not part of a corosync cluster, the leader is
determined as being "the alive unit with the lowest unit numer". In
other words, the oldest surviving unit.
"""
try:
return juju_is_leader()
except NotImplementedError:
log('Juju leadership election feature not enabled'
', using fallback support',
level=WARNING)
if is_clustered():
if not is_crm_leader(resource):
log('Deferring action to CRM leader.', level=INFO)
return False
else:
peers = peer_units()
if peers and not oldest_peer(peers):
log('Deferring action to oldest service unit.', level=INFO)
return False
return True
def distributed_wait(modulo=None, wait=None, operation_name='operation'):
''' Distribute operations by waiting based on modulo_distribution
If modulo and or wait are not set, check config_get for those values.
If config values are not set, default to modulo=3 and wait=30.
:param modulo: int The modulo number creates the group distribution
:param wait: int The constant time wait value
:param operation_name: string Operation name for status message
i.e. 'restart'
:side effect: Calls config_get()
:side effect: Calls log()
:side effect: Calls status_set()
:side effect: Calls time.sleep()
'''
if modulo is None:
modulo = config_get('modulo-nodes') or 3
if wait is None:
wait = config_get('known-wait') or 30
if juju_is_leader():
# The leader should never wait
calculated_wait = 0
else:
# non_zero_wait=True guarantees the non-leader who gets modulo 0
# will still wait
calculated_wait = modulo_distribution(modulo=modulo,
wait=wait,
non_zero_wait=True)
msg = "Waiting {} seconds for {} ...".format(calculated_wait,
operation_name)
log(msg, DEBUG)
status_set('maintenance', msg)
time.sleep(calculated_wait)
def distributed_wait(modulo=None, wait=None, operation_name='operation'):
''' Distribute operations by waiting based on modulo_distribution
If modulo and or wait are not set, check config_get for those values.
If config values are not set, default to modulo=3 and wait=30.
:param modulo: int The modulo number creates the group distribution
:param wait: int The constant time wait value
:param operation_name: string Operation name for status message
i.e. 'restart'
:side effect: Calls config_get()
:side effect: Calls log()
:side effect: Calls status_set()
:side effect: Calls time.sleep()
'''
if modulo is None:
modulo = config_get('modulo-nodes') or 3
if wait is None:
wait = config_get('known-wait') or 30
if juju_is_leader():
# The leader should never wait
calculated_wait = 0
else:
# non_zero_wait=True guarantees the non-leader who gets modulo 0
# will still wait
calculated_wait = modulo_distribution(modulo=modulo, wait=wait,
non_zero_wait=True)
msg = "Waiting {} seconds for {} ...".format(calculated_wait,
operation_name)
log(msg, DEBUG)
status_set('maintenance', msg)
time.sleep(calculated_wait)