coordination: implement lock mechanism in ZK

Change-Id: I0372200abbb79d2812a0e89317518e58d754845a
Co-Authored-By: Sahid Ferdjaoui <sahid.ferdjaoui@cloudwatt.com>

tooz/coordination.py

@@ -267,6 +267,16 @@ class CoordinationDriver(object):
         """
         raise NotImplementedError
 
+    @staticmethod
+    def get_lock(name):
+        """Return a distributed lock.
+
+        :param name: The lock name that is used to identify it across all
+                     nodes.
+
+        """
+        raise NotImplementedError
+
     @staticmethod
     def heartbeat():
         """Method to run once in a while to be sure that the member is not dead

tooz/drivers/zookeeper.py

@@ -24,6 +24,19 @@ import six
 from zake import fake_client
 
 from tooz import coordination
+from tooz import locking
+
+
+class ZooKeeperLock(locking.Lock):
+    def __init__(self, lock):
+        self._lock = lock
+
+    def acquire(self, blocking=True, timeout=None):
+        return self._lock.acquire(blocking=blocking,
+                                  timeout=timeout)
+
+    def release(self):
+        return self._lock.release()
 
 
 class BaseZooKeeperDriver(coordination.CoordinationDriver):
@@ -317,6 +330,12 @@ class KazooDriver(BaseZooKeeperDriver):
             leader = None
         return ZooAsyncResult(None, lambda *args: leader)
 
+    def get_lock(self, name):
+        return ZooKeeperLock(
+            self._coord.Lock(
+                self.paths_join(b"/", self._TOOZ_NAMESPACE, b"locks", name),
+                self._member_id.decode('ascii')))
+
     def run_watchers(self):
         ret = []
         while True:

tooz/locking.py

@@ -0,0 +1,35 @@
+# -*- coding: utf-8 -*-
+#
+#    Copyright (C) 2014 eNovance Inc. All Rights Reserved.
+#
+#    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 abc
+
+import six
+
+
+@six.add_metaclass(abc.ABCMeta)
+class Lock(object):
+    def __enter__(self):
+        self.acquire()
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        self.release()
+
+    @abc.abstractmethod
+    def release(self):
+        pass
+
+    @abc.abstractmethod
+    def acquire(self):
+        pass

tooz/tests/test_coordination.py

@@ -457,6 +457,29 @@ class TestAPI(testscenarios.TestWithScenarios,
         self.assertEqual(self.group_id,
                          self.event.group_id)
 
+    def test_get_lock(self):
+        lock = self._coord.get_lock(self._get_random_uuid())
+        self.assertEqual(True, lock.acquire())
+        lock.release()
+        with lock:
+            pass
+
+    def test_get_lock_multiple_coords(self):
+        member_id2 = self._get_random_uuid()
+        client2 = tooz.coordination.get_coordinator(self.backend,
+                                                    member_id2,
+                                                    **self.kwargs)
+        client2.start()
+
+        lock_name = self._get_random_uuid()
+        lock = self._coord.get_lock(lock_name)
+        self.assertEqual(True, lock.acquire())
+
+        lock2 = client2.get_lock(lock_name)
+        self.assertEqual(False, lock2.acquire(blocking=False))
+        lock.release()
+        self.assertEqual(True, lock2.acquire(blocking=False))
+
     @staticmethod
     def _get_random_uuid():
         return str(uuid.uuid4()).encode('ascii')