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# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
import uuid
from etcd3gw.utils import _encode
from etcd3gw.utils import DEFAULT_TIMEOUT
from etcd3gw.utils import LOCK_PREFIX
class Lock(object):
def __init__(self, name, ttl=DEFAULT_TIMEOUT, client=None):
"""Create a lock using the given name with specified timeout
:param name:
:param ttl:
:param client:
"""
self.name = name
self.ttl = ttl
self.client = client
self.key = LOCK_PREFIX + self.name
self.lease = None
self._uuid = str(uuid.uuid1())
@property
def uuid(self):
"""The unique id of the lock"""
return self._uuid
def acquire(self):
"""Acquire the lock."""
self.lease = self.client.lease(self.ttl)
base64_key = _encode(self.key)
base64_value = _encode(self._uuid)
txn = {
'compare': [{
'key': base64_key,
'result': 'EQUAL',
'target': 'CREATE',
'create_revision': 0
}],
'success': [{
'request_put': {
'key': base64_key,
'value': base64_value,
'lease': self.lease.id
}
}],
'failure': [{
'request_range': {
'key': base64_key
}
}]
}
result = self.client.transaction(txn)
if 'succeeded' in result:
return result['succeeded']
return False
def release(self):
"""Release the lock"""
base64_key = _encode(self.key)
base64_value = _encode(self._uuid)
txn = {
'compare': [{
'key': base64_key,
'result': 'EQUAL',
'target': 'VALUE',
'value': base64_value
}],
'success': [{
'request_delete_range': {
'key': base64_key
}
}]
}
result = self.client.transaction(txn)
if 'succeeded' in result:
return result['succeeded']
return False
def refresh(self):
"""Refresh the lease on the lock
:return:
"""
return self.lease.refresh()
def is_acquired(self):
"""Check if the lock is acquired"""
values = self.client.get(self.key)
return self._uuid.encode("latin-1") in values
def __enter__(self):
"""Use the lock as a contextmanager"""
self.acquire()
return self
def __exit__(self, exception_type, exception_value, traceback):
self.release()
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