DRBD: new option "drbdmanage_devs_on_controller".

With this option set the c-vol node will have all volumes accessible,
via DRBD-client if no local copy already exists anyway.

This is handy for a) debugging b) maintenance c) iSCSI exports
and other use cases.

Change-Id: Ib347777d2f4bb8b46990d76e138e1dbf13ff95bb

cinder/tests/unit/test_drbdmanagedrv.py

@@ -161,6 +161,10 @@ class DrbdManageFakeDriver(object):
         self.calls.append(["restore_snapshot", res, snap, new, rprop, vprops])
         return [[mock_dm_exc.DM_SUCCESS, "ack", []]]
 
+    def assign(self, host, resource, props):
+        self.calls.append(["assign", host, resource, props])
+        return [[mock_dm_exc.DM_SUCCESS, "ack", []]]
+
 
 class DrbdManageTestCase(test.TestCase):
 
@@ -215,6 +219,7 @@ class DrbdManageTestCase(test.TestCase):
                    'created_at': timeutils.utcnow()}
 
         dmd = drbdmanagedrv.DrbdManageDriver(configuration=self.configuration)
+        dmd.drbdmanage_devs_on_controller = False
         dmd.odm = DrbdManageFakeDriver()
         dmd.create_volume(testvol)
         self.assertEqual("create_resource", dmd.odm.calls[0][0])
@@ -222,6 +227,27 @@ class DrbdManageTestCase(test.TestCase):
         self.assertEqual("create_volume", dmd.odm.calls[2][0])
         self.assertEqual(1048576, dmd.odm.calls[2][2])
         self.assertEqual("auto_deploy", dmd.odm.calls[3][0])
+        self.assertEqual(len(dmd.odm.calls), 4)
+
+    def test_create_volume_controller_all_vols(self):
+        testvol = {'project_id': 'testprjid',
+                   'name': 'testvol',
+                   'size': 1,
+                   'id': 'deadbeef-8068-11e4-98c0-5254008ea111',
+                   'volume_type_id': 'drbdmanage',
+                   'created_at': timeutils.utcnow()}
+
+        dmd = drbdmanagedrv.DrbdManageDriver(configuration=self.configuration)
+        dmd.drbdmanage_devs_on_controller = True
+        dmd.odm = DrbdManageFakeDriver()
+        dmd.create_volume(testvol)
+        self.assertEqual("create_resource", dmd.odm.calls[0][0])
+        self.assertEqual("list_volumes", dmd.odm.calls[1][0])
+        self.assertEqual("create_volume", dmd.odm.calls[2][0])
+        self.assertEqual(1048576, dmd.odm.calls[2][2])
+        self.assertEqual("auto_deploy", dmd.odm.calls[3][0])
+        self.assertEqual("assign", dmd.odm.calls[4][0])
+        self.assertEqual(len(dmd.odm.calls), 5)
 
     def test_delete_volume(self):
         testvol = {'project_id': 'testprjid',

cinder/volume/drivers/drbdmanagedrv.py

@@ -24,6 +24,7 @@ for more details.
 """
 
 import six
+import socket
 import uuid
 
 from oslo_config import cfg
@@ -54,6 +55,13 @@ drbd_opts = [
     cfg.StrOpt('drbdmanage_redundancy',
                default='1',
                help='Number of nodes that should replicate the data.'),
+    cfg.BoolOpt('drbdmanage_devs_on_controller',
+                default=True,
+                help='''If set, the c-vol node will receive a useable
+                /dev/drbdX device, even if the actual data is stored on
+                other nodes only.
+                This is useful for debugging, maintenance, and to be
+                able to do the iSCSI export from the c-vol node.''')
     # TODO(PM): offsite_redundancy?
     # TODO(PM): choose DRBDmanage storage pool?
 ]
@@ -86,6 +94,10 @@ class DrbdManageDriver(driver.VolumeDriver):
             self.drbdmanage_dbus_interface = '/interface'
         self.drbdmanage_redundancy = int(getattr(self.configuration,
                                                  'drbdmanage_redundancy', 1))
+        self.drbdmanage_devs_on_controller = bool(
+            getattr(self.configuration,
+                    'drbdmanage_devs_on_controller',
+                    True))
         self.dm_control_vol = ".drbdctrl"
 
         # Copied from the LVM driver, see
@@ -336,6 +348,14 @@ class DrbdManageDriver(driver.VolumeDriver):
                                      0, True)
         self._check_result(res)
 
+        if self.drbdmanage_devs_on_controller:
+            # FIXME: Consistency groups, vol#
+            res = self.call_or_reconnect(self.odm.assign,
+                                         socket.gethostname(),
+                                         dres,
+                                         self.empty_dict)
+            self._check_result(res, ignore=[dm_exc.DM_EEXIST])
+
         return 0
 
     def delete_volume(self, volume):