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import etcd
import platform
class LeaderElection(object):
"""
Leader Election class using the etcd module
"""
def __init__(self, client):
"""
Initialize a leader election object.
Args:
client (etcd.Client): etcd client to use for the connection
"""
self.client = client
def get_path(self, key):
if key.startswith('/'):
return '/mod/v2/leader{}'.format(key)
return '/mod/v2/leader/{}'.format(key)
def set(self, key, name=None, ttl=0, timeout=None):
"""
Initialize a leader election object.
Args:
key (string): name of the leader key,
ttl (int): ttl (in seconds) for the lock to live.
name (string): the name to store as the leader name. Defaults to the
client's hostname
"""
name = name or platform.node()
params = {'ttl': ttl, 'name': name}
path = self.get_path(key)
res = self.client.api_execute(
path, self.client._MPUT, params=params, timeout=timeout)
return res.data.decode('utf-8')
def get(self, key):
"""
Get the name of a leader object.
Args:
key (string): name of the leader key,
Raises:
etcd.EtcdException
"""
res = self.client.api_execute(self.get_path(key), self.client._MGET)
if not res.data:
raise etcd.EtcdException('Leader path {} not found'.format(key))
return res.data.decode('utf-8')
def delete(self, key, name=None):
"""
Delete a leader object.
Args:
key (string): the leader key,
name (string): name of the elected leader
Raises:
etcd.EtcdException
"""
path = self.get_path(key)
name = name or platform.node()
res = self.client.api_execute(path, self.client._MDELETE, {'name': name})
return res.data.decode('utf-8') == ''
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