1 files changed, 107 insertions, 0 deletions
diff --git a/designate/common/decorators/lock.py b/designate/common/decorators/lock.py
new file mode 100644
index 00000000..f633fa4d
--- /dev/null
+++ b/designate/common/decorators/lock.py
@@ -0,0 +1,107 @@
+# 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 functools
+import itertools
+import threading
+
+from oslo_log import log as logging
+
+from designate import objects
+
+LOG = logging.getLogger(__name__)
+
+
+class ZoneLockLocal(threading.local):
+    def __init__(self):
+        super(ZoneLockLocal, self).__init__()
+        self._held = set()
+
+    def hold(self, name):
+        self._held.add(name)
+
+    def release(self, name):
+        self._held.remove(name)
+
+    def has_lock(self, name):
+        return name in self._held
+
+
+def extract_zone_id(args, kwargs):
+    zone_id = None
+
+    if 'zone_id' in kwargs:
+        zone_id = kwargs['zone_id']
+    elif 'zone' in kwargs:
+        zone_id = kwargs['zone'].id
+    elif 'recordset' in kwargs:
+        zone_id = kwargs['recordset'].zone_id
+    elif 'record' in kwargs:
+        zone_id = kwargs['record'].zone_id
+
+    if not zone_id:
+        for arg in itertools.chain(args, kwargs.values()):
+            if not isinstance(arg, objects.DesignateObject):
+                continue
+            if isinstance(arg, objects.Zone):
+                zone_id = arg.id
+                if zone_id:
+                    break
+            elif isinstance(arg, (objects.RecordSet,
+                                  objects.Record,
+                                  objects.ZoneTransferRequest,
+                                  objects.ZoneTransferAccept)):
+                zone_id = arg.zone_id
+                if zone_id:
+                    break
+
+    if not zone_id and len(args) > 1:
+        arg = args[1]
+        if isinstance(arg, str):
+            zone_id = arg
+        elif isinstance(zone_id, objects.Zone):
+            zone_id = arg.id
+
+    return zone_id
+
+
+def synchronized_zone(new_zone=False):
+    """Ensures only a single operation is in progress for each zone
+
+    A Decorator which ensures only a single operation can be happening
+    on a single zone at once, within the current designate-central instance
+    """
+    def outer(f):
+        @functools.wraps(f)
+        def sync_wrapper(cls, *args, **kwargs):
+            if new_zone is True:
+                lock_name = 'create-new-zone'
+            else:
+                zone_id = extract_zone_id(args, kwargs)
+                if zone_id:
+                    lock_name = 'zone-%s' % zone_id
+                else:
+                    raise Exception('Failed to determine zone id for '
+                                    'synchronized operation')
+
+            if cls.zone_lock_local.has_lock(lock_name):
+                return f(cls, *args, **kwargs)
+
+            with cls.coordination.get_lock(lock_name):
+                try:
+                    cls.zone_lock_local.hold(lock_name)
+                    return f(cls, *args, **kwargs)
+                finally:
+                    cls.zone_lock_local.release(lock_name)
+
+        return sync_wrapper
+    return outer