Connecting Nova to DRBD storage nodes directly

Our DRBD block storage driver for Cinder can be used to make
Nova directly connect to the DRBD 9 storage servers, instead
of needing an iSCSI hop.

Co-Authored-By: Matt Riedemann <mriedem.os@gmail.com>

Change-Id: I60477778a73701794db0c0860183ea9ab144040b
Implements: blueprint drbd-driver

nova/tests/unit/virt/libvirt/volume/test_drbd.py

@@ -0,0 +1,63 @@
+# Copyright (c) 2015 LINBIT HA-Solutions GmbH.
+# 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.
+"""Unit tests for the DRDB volume driver module."""
+
+import mock
+from os_brick.initiator import connector
+
+from nova import context as nova_context
+from nova.tests.unit import fake_instance
+from nova.tests.unit.virt.libvirt.volume import test_volume
+from nova.virt.libvirt.volume import drbd
+
+
+class LibvirtDRBDVolumeDriverTestCase(
+        test_volume.LibvirtVolumeBaseTestCase):
+    """Tests the LibvirtDRBDVolumeDriver class."""
+
+    def test_libvirt_drbd_driver(self):
+        drbd_driver = drbd.LibvirtDRBDVolumeDriver(self.fake_host)
+        self.assertIsInstance(drbd_driver.connector, connector.DRBDConnector)
+        # connect a fake volume
+        connection_info = {
+            'data': {
+                'device': '/path/to/fake-device'
+            }
+        }
+        ctxt = nova_context.RequestContext('fake-user', 'fake-project')
+        instance = fake_instance.fake_instance_obj(ctxt)
+        device_info = {
+            'type': 'block',
+            'path': connection_info['data']['device'],
+        }
+        with mock.patch.object(connector.DRBDConnector, 'connect_volume',
+                               return_value=device_info):
+            drbd_driver.connect_volume(
+                connection_info, self.disk_info, instance)
+        # assert that the device_path was set
+        self.assertIn('device_path', connection_info['data'])
+        self.assertEqual('/path/to/fake-device',
+                         connection_info['data']['device_path'])
+        # now get the config using the updated connection_info
+        conf = drbd_driver.get_config(connection_info, self.disk_info)
+        # assert things were passed through to the parent class
+        self.assertEqual('block', conf.source_type)
+        self.assertEqual('/path/to/fake-device', conf.source_path)
+        # now disconnect the volume
+        with mock.patch.object(connector.DRBDConnector,
+                               'disconnect_volume') as mock_disconnect:
+            drbd_driver.disconnect_volume(connection_info, 'vda', instance)
+        # disconnect is all passthrough so just assert the call
+        mock_disconnect.assert_called_once_with(connection_info['data'], None)

nova/virt/libvirt/driver.py

@@ -150,6 +150,7 @@ libvirt_volume_drivers = [
     'iscsi=nova.virt.libvirt.volume.iscsi.LibvirtISCSIVolumeDriver',
     'iser=nova.virt.libvirt.volume.iser.LibvirtISERVolumeDriver',
     'local=nova.virt.libvirt.volume.volume.LibvirtVolumeDriver',
+    'drbd=nova.virt.libvirt.volume.drbd.LibvirtDRBDVolumeDriver',
     'fake=nova.virt.libvirt.volume.volume.LibvirtFakeVolumeDriver',
     'rbd=nova.virt.libvirt.volume.net.LibvirtNetVolumeDriver',
     'sheepdog=nova.virt.libvirt.volume.net.LibvirtNetVolumeDriver',

nova/virt/libvirt/volume/drbd.py

@@ -0,0 +1,61 @@
+#    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.
+
+from os_brick.initiator import connector
+from oslo_log import log as logging
+
+from nova import utils
+from nova.virt.libvirt.volume import volume as libvirt_volume
+
+
+LOG = logging.getLogger(__name__)
+
+
+class LibvirtDRBDVolumeDriver(libvirt_volume.LibvirtVolumeDriver):
+    """Driver to attach DRBD volumes to libvirt."""
+
+    def __init__(self, host):
+        super(LibvirtDRBDVolumeDriver, self).__init__(host)
+        self.connector = connector.InitiatorConnector.factory(
+            connector.DRBD, utils.get_root_helper())
+
+    def connect_volume(self, connection_info, disk_info, instance):
+        """Connect the volume.
+
+        Sets the connection_info['data']['device_path'] value upon successful
+        connection.
+
+        :param connection_info: dict of connection information for the backend
+            storage when a connection was initiated with Cinder. Expects
+            connection_info['data']['device'] to be set.
+        :param disk_info: dict of block device information (not used).
+        :param instance: The nova.objects.Instance that is having a volume
+            connected to it.
+        """
+        LOG.debug("Calling os-brick to attach DRBD Volume.", instance=instance)
+        device_info = self.connector.connect_volume(connection_info['data'])
+        LOG.debug("Attached DRBD volume %s", device_info, instance=instance)
+        connection_info['data']['device_path'] = device_info['path']
+
+    def disconnect_volume(self, connection_info, disk_dev, instance):
+        """Disconnect the volume.
+
+        :param connection_info: dict of connection information for the backend
+            storage when a connection was initiated with Cinder.
+        :param disk_dev: The block device mountpoint device name (not path).
+            This is currently not used by this method.
+        :param instance: The nova.objects.Instance that is having a volume
+            disconnected from it.
+        """
+        LOG.debug("Calling os-brick to detach DRBD Volume.", instance=instance)
+        self.connector.disconnect_volume(connection_info['data'], None)
+        LOG.debug("Disconnected DRBD Volume %s", disk_dev, instance=instance)

releasenotes/notes/drbd-libvirt-volume-driver-d27c79e62c0beb64.yaml

@@ -0,0 +1,7 @@
+---
+features:
+  - |
+    The libvirt compute driver now supports attaching volumes of type "drbd".
+    See the `DRBD documentation`_ for more information.
+
+    .. _DRBD documentation: http://docs.linbit.com/docs/users-guide-9.0/p-apps/#s-openstack-transport-protocol