etcd3: replace custom lock code by more recent etcd3 lock code

The code in python-etcd3 for locks has been adjusted to reflect how tooz wants
his lock to work. That's amazing because now we can use them directly and not
implement our own locking mechanism!

Change-Id: Ia5741bae83cddd90f9bb78fba9173dca8509e6d9

setup.cfg

@@ -45,7 +45,7 @@ consul =
 etcd =
   requests>=2.10.0 # Apache-2.0
 etcd3 =
-  etcd3>=0.5.1 # Apache-2.0
+  etcd3>=0.6.2 # Apache-2.0
 etcd3gw =
   etcd3gw>=0.1.0 # Apache-2.0
 zake =

tooz/drivers/etcd3.py

@@ -13,7 +13,6 @@
 # under the License.
 
 from __future__ import absolute_import
-import uuid
 
 import etcd3
 from etcd3 import exceptions as etcd3_exc
@@ -21,7 +20,6 @@ from oslo_utils import encodeutils
 import six
 
 import tooz
-from tooz import _retry
 from tooz import coordination
 from tooz import locking
 from tooz import utils
@@ -61,67 +59,38 @@ class Etcd3Lock(locking.Lock):
 
     def __init__(self, coord, name, timeout):
         super(Etcd3Lock, self).__init__(name)
-        self._timeout = timeout
         self._coord = coord
-        self._key = self.LOCK_PREFIX + name
-        self._uuid = uuid.uuid4().bytes
-        self._lease = self._coord.client.lease(self._timeout)
+        self._lock = coord.client.lock(name.decode(), timeout)
 
     @_translate_failures
     def acquire(self, blocking=True, shared=False):
         if shared:
             raise tooz.NotImplemented
 
-        @_retry.retry(stop_max_delay=blocking)
-        def _acquire():
-            # TODO(jd): save the created revision so we can check it later to
-            # make sure we still have the lock
-            success, _ = self._coord.client.transaction(
-                compare=[
-                    self._coord.client.transactions.create(self._key) == 0
-                ],
-                success=[
-                    self._coord.client.transactions.put(self._key, self._uuid,
-                                                        lease=self._lease)
-                ],
-                failure=[
-                    self._coord.client.transactions.get(self._key)
-                ],
-            )
-            if success is not True:
-                if blocking is False:
-                    return False
-                raise _retry.TryAgain
+        blocking, timeout = utils.convert_blocking(blocking)
+        if blocking is False:
+            timeout = 0
+
+        if self._lock.acquire(timeout):
             self._coord._acquired_locks.add(self)
             return True
 
-        return _acquire()
+        return False
+
+    @property
+    def acquired(self):
+        return self in self._coord._acquired_locks
 
     @_translate_failures
     def release(self):
-        success, _ = self._coord.client.transaction(
-            compare=[
-                self._coord.client.transactions.value(self._key) == self._uuid
-            ],
-            success=[self._coord.client.transactions.delete(self._key)],
-            failure=[],
-        )
-        if success:
-            self._coord._acquired_locks.remove(self)
+        if self.acquired and self._lock.release():
+            self._coord._acquired_locks.discard(self)
             return True
         return False
 
-    @_translate_failures
-    def break_(self):
-        # FIXME(jd) when pyetcd3 returns the status
-        # https://github.com/kragniz/python-etcd3/pull/126
-        self._coord.client.delete(self._key)
-        self._coord._acquired_locks.discard(self)
-        return True
-
     @_translate_failures
     def heartbeat(self):
-        self._lease.refresh()
+        self._lock.refresh()
 
 
 class Etcd3Driver(coordination.CoordinationDriver):