Merge "Raise exception on failed lock's CM acquire fail"

tooz/coordination.py

@@ -436,6 +436,10 @@ class OperationTimedOut(ToozError):
     """Exception raised when an operation times out."""
 
 
+class LockAcquireFailed(ToozError):
+    """Exception raised when a lock acquire fails in a context manager."""
+
+
 class GroupNotCreated(ToozError):
     """Exception raised when the caller request a group which does
     not exist.

tooz/locking.py

@@ -19,6 +19,8 @@ import six
 import threading
 import weakref
 
+from tooz import coordination
+
 
 @six.add_metaclass(abc.ABCMeta)
 class Lock(object):
@@ -32,7 +34,12 @@ class Lock(object):
         return self._name
 
     def __enter__(self):
-        self.acquire()
+        acquired = self.acquire()
+        if not acquired:
+            msg = u'Acquiring lock %s failed' % self.name
+            raise coordination.LockAcquireFailed(msg)
+
+        return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         self.release()

tooz/tests/test_coordination.py

@@ -21,6 +21,7 @@ import uuid
 
 from concurrent import futures
 import fixtures
+import mock
 import testscenarios
 from testtools import matchers
 from testtools import testcase
@@ -682,6 +683,22 @@ class TestAPI(testscenarios.TestWithScenarios,
         with lock1:
             self.assertFalse(lock2.acquire(blocking=False))
 
+    def test_get_lock_context_fails(self):
+        name = self._get_random_uuid()
+        lock1 = self._coord.get_lock(name)
+        lock2 = self._coord.get_lock(name)
+        with mock.patch.object(lock2, 'acquire', return_value=False):
+            with lock1:
+                self.assertRaises(
+                    tooz.coordination.LockAcquireFailed,
+                    lock2.__enter__)
+
+    def test_get_lock_context_check_value(self):
+        name = self._get_random_uuid()
+        lock = self._coord.get_lock(name)
+        with lock as returned_lock:
+            self.assertEqual(lock, returned_lock)
+
     def test_get_lock_locked_twice(self):
         name = self._get_random_uuid()
         lock = self._coord.get_lock(name)