Implementation for XenServer migrations. There are several places for optimization but I based the current implementation on the chance scheduler just to be safe. Beyond that, a few features are missing, such as ensuring the IP address is transferred along with the migrated instance. This will be added in a subsequent patch. Finally, everything is implemented through the Openstack API resize hooks, but actual resizing of the instance RAM and hard drive space is not yet implemented.

nova/api/openstack/servers.py

@@ -203,10 +203,58 @@ class Controller(wsgi.Controller):
         return exc.HTTPNoContent()
 
     def action(self, req, id):
-        """ Multi-purpose method used to reboot, rebuild, and
-        resize a server """
+        """Multi-purpose method used to reboot, rebuild, or
+        resize a server"""
+
+        actions = {
+            'reboot':        self._action_reboot,
+            'resize':        self._action_resize,
+            'confirmResize': self._action_confirm_resize,
+            'revertResize':  self._action_revert_resize,
+            'rebuild':       self._action_rebuild,
+            }
+
         input_dict = self._deserialize(req.body, req)
-        #TODO(sandy): rebuild/resize not supported.
+        for key in actions.keys():
+            if key in input_dict:
+                return actions[key](input_dict, req, id)
+        return faults.Fault(exc.HTTPNotImplemented())
+
+    def _action_confirm_resize(self, input_dict, req, id):
+        try:
+            self.compute_api.confirm_resize(req.environ['nova.context'], id)
+        except Exception, e:
+            LOG.exception(_("Error in confirm-resize %s"), e)
+            return faults.Fault(exc.HTTPBadRequest())
+        return exc.HTTPNoContent()
+
+    def _action_revert_resize(self, input_dict, req, id):
+        try:
+            self.compute_api.revert_resize(req.environ['nova.context'], id)
+        except Exception, e:
+            LOG.exception(_("Error in revert-resize %s"), e)
+            return faults.Fault(exc.HTTPBadRequest())
+        return exc.HTTPAccepted()
+
+    def _action_rebuild(self, input_dict, req, id):
+        return faults.Fault(exc.HTTPNotImplemented())
+
+    def _action_resize(self, input_dict, req, id):
+        """ Resizes a given instance to the flavor size requested """
+        try:
+            if 'resize' in input_dict and 'flavorId' in input_dict['resize']:
+                flavor_id = input_dict['resize']['flavorId']
+                self.compute_api.resize(req.environ['nova.context'], id,
+                        flavor_id)
+            else:
+                LOG.exception(_("Missing arguments for resize"))
+                return faults.Fault(exc.HTTPUnprocessableEntity())
+        except Exception, e:
+            LOG.exception(_("Error in resize %s"), e)
+            return faults.Fault(exc.HTTPBadRequest())
+        return faults.Fault(exc.HTTPAccepted())
+
+    def _action_reboot(self, input_dict, req, id):
         try:
             reboot_type = input_dict['reboot']['type']
         except Exception:

nova/compute/api.py

@@ -404,6 +404,10 @@ class API(base.Base):
         kwargs = {'method': method, 'args': params}
         return rpc.call(context, queue, kwargs)
 
+    def _cast_scheduler_message(self, context, args):
+        """Generic handler for RPC calls to the scheduler"""
+        rpc.cast(context, FLAGS.scheduler_topic, args)
+
     def snapshot(self, context, instance_id, name):
         """Snapshot the given instance.
 
@@ -420,6 +424,45 @@ class API(base.Base):
         """Reboot the given instance."""
         self._cast_compute_message('reboot_instance', context, instance_id)
 
+    def revert_resize(self, context, instance_id):
+        """Reverts a resize, deleting the 'new' instance in the process"""
+        context = context.elevated()
+        migration_ref = self.db.migration_get_by_instance_and_status(context,
+                instance_id, 'finished')
+        if not migration_ref:
+            raise exception.NotFound(_("No finished migrations found for "
+                    "instance"))
+
+        params = {'migration_id': migration_ref['id']}
+        self._cast_compute_message('revert_resize', context, instance_id,
+                migration_ref['dest_compute'], params=params)
+
+    def confirm_resize(self, context, instance_id):
+        """Confirms a migration/resize, deleting the 'old' instance in the
+        process."""
+        context = context.elevated()
+        migration_ref = self.db.migration_get_by_instance_and_status(context,
+                instance_id, 'finished')
+        if not migration_ref:
+            raise exception.NotFound(_("No finished migrations found for "
+                    "instance"))
+        instance_ref = self.db.instance_get(context, instance_id)
+        params = {'migration_id': migration_ref['id']}
+        self._cast_compute_message('confirm_resize', context, instance_id,
+                migration_ref['source_compute'], params=params)
+
+        self.db.migration_update(context, migration_id,
+                {'status': 'confirmed'})
+        self.db.instance_update(context, instance_id,
+                {'host': migration_ref['dest_compute'], })
+
+    def resize(self, context, instance_id, flavor):
+        """Resize a running instance."""
+        self._cast_scheduler_message(context,
+                    {"method": "prep_resize",
+                     "args": {"topic": FLAGS.compute_topic,
+                              "instance_id": instance_id, }},)
+
     def pause(self, context, instance_id):
         """Pause the given instance."""
         self._cast_compute_message('pause_instance', context, instance_id)

nova/compute/manager.py

@@ -411,6 +411,112 @@ class ComputeManager(manager.Manager):
         """Update instance state when async task completes."""
         self._update_state(context, instance_id)
 
+    @exception.wrap_exception
+    @checks_instance_lock
+    def confirm_resize(self, context, instance_id, migration_id):
+        """Destroys the source instance"""
+        context = context.elevated()
+        instance_ref = self.db.instance_get(context, instance_id)
+        migration_ref = self.db.migration_get(context, migration_id)
+        self.driver.destroy(instance_ref)
+
+    @exception.wrap_exception
+    @checks_instance_lock
+    def revert_resize(self, context, instance_id, migration_id):
+        """Destroys the new instance on the destination machine,
+        reverts the model changes, and powers on the old
+        instance on the source machine"""
+        instance_ref = self.db.instance_get(context, instance_id)
+        migration_ref = self.db.migration_get(context, migration_id)
+
+        #TODO(mdietz): we may want to split these into separate methods.
+        if migration_ref['source_compute'] == FLAGS.host:
+            self.driver._start(instance_ref)
+            self.db.migration_update(context, migration_id,
+                    {'status': 'reverted'})
+        else:
+            self.driver.destroy(instance_ref)
+            topic = self.db.queue_get_for(context, FLAGS.compute_topic,
+                    instance_ref['host'])
+            rpc.cast(context, topic,
+                    {'method': 'revert_resize',
+                     'args': {
+                           'migration_id': migration_ref['id'],
+                           'instance_id': instance_id, },
+                    })
+
+    @exception.wrap_exception
+    @checks_instance_lock
+    def prep_resize(self, context, instance_id):
+        """Initiates the process of moving a running instance to another
+        host, possibly changing the RAM and disk size in the process"""
+        context = context.elevated()
+        instance_ref = self.db.instance_get(context, instance_id)
+        if instance_ref['host'] == FLAGS.host:
+            raise exception.Error(_(
+                    'Migration error: destination same as source!'))
+
+        migration_ref = self.db.migration_create(context,
+                {'instance_id': instance_id,
+                 'source_compute': instance_ref['host'],
+                 'dest_compute': FLAGS.host,
+                 'dest_host':   self.driver.get_host_ip_addr(),
+                 'status':      'pre-migrating'})
+        LOG.audit(_('instance %s: migrating to '), instance_id,
+                context=context)
+        topic = self.db.queue_get_for(context, FLAGS.compute_topic,
+                instance_ref['host'])
+        rpc.cast(context, topic,
+                {'method': 'resize_instance',
+                 'args': {
+                       'migration_id': migration_ref['id'],
+                       'instance_id': instance_id, },
+                })
+
+    @exception.wrap_exception
+    @checks_instance_lock
+    def resize_instance(self, context, instance_id, migration_id):
+        """Starts the migration of a running instance to another host"""
+        migration_ref = self.db.migration_get(context, migration_id)
+        instance_ref = self.db.instance_get(context, instance_id)
+        self.db.migration_update(context, migration_id,
+                {'status': 'migrating', })
+
+        disk_info = self.driver.migrate_disk_and_power_off(instance_ref,
+                                  migration_ref['dest_host'])
+        self.db.migration_update(context, migration_id,
+                {'status': 'post-migrating', })
+
+        #TODO(mdietz): This is where we would update the VM record
+        #after resizing
+        service = self.db.service_get_by_host_and_topic(context,
+                migration_ref['dest_compute'], FLAGS.compute_topic)
+        topic = self.db.queue_get_for(context, FLAGS.compute_topic,
+                migration_ref['dest_compute'])
+        rpc.cast(context, topic,
+                {'method': 'finish_resize',
+                 'args': {
+                       'migration_id': migration_id,
+                       'instance_id': instance_id,
+                       'disk_info': disk_info, },
+                })
+
+    @exception.wrap_exception
+    @checks_instance_lock
+    def finish_resize(self, context, instance_id, migration_id, disk_info):
+        """Completes the migration process by setting up the newly transferred
+        disk and turning on the instance on its new host machine"""
+        migration_ref = self.db.migration_get(context, migration_id)
+        instance_ref = self.db.instance_get(context,
+                migration_ref['instance_id'])
+
+        # this may get passed into the following spawn instead
+        new_disk_info = self.driver.attach_disk(instance_ref, disk_info)
+        self.driver.spawn(instance_ref, disk=new_disk_info)
+
+        self.db.migration_update(context, migration_id,
+                {'status': 'finished', })
+
     @exception.wrap_exception
     @checks_instance_lock
     def pause_instance(self, context, instance_id):

nova/db/api.py

@@ -80,10 +80,15 @@ def service_destroy(context, instance_id):
 
 
 def service_get(context, service_id):
-    """Get an service or raise if it does not exist."""
+    """Get a service or raise if it does not exist."""
     return IMPL.service_get(context, service_id)
 
 
+def service_get_by_host_and_topic(context, host, topic):
+    """Get a service by host it's on and topic it listens to"""
+    return IMPL.service_get_by_host_and_topic(context, host, topic)
+
+
 def service_get_all(context, disabled=False):
     """Get all services."""
     return IMPL.service_get_all(context, disabled)
@@ -254,6 +259,28 @@ def floating_ip_get_by_address(context, address):
 
 ####################
 
+def migration_update(context, id, values):
+    """Update a migration instance"""
+    return IMPL.migration_update(context, id, values)
+
+
+def migration_create(context, values):
+    """Create a migration record"""
+    return IMPL.migration_create(context, values)
+
+
+def migration_get(context, migration_id):
+    """Finds a migration by the id"""
+    return IMPL.migration_get(context, migration_id)
+
+
+def migration_get_by_instance_and_status(context, instance_id, status):
+    """Finds a migration by the instance id its migrating"""
+    return IMPL.migration_get_by_instance_and_status(context, instance_id,
+            status)
+
+####################
+
 
 def fixed_ip_associate(context, address, instance_id):
     """Associate fixed ip to instance.

nova/db/sqlalchemy/api.py

@@ -154,6 +154,17 @@ def service_get_all_by_topic(context, topic):
                    all()
 
 
+@require_admin_context
+def service_get_by_host_and_topic(context, host, topic):
+    session = get_session()
+    return session.query(models.Service).\
+                   filter_by(deleted=False).\
+                   filter_by(disabled=False).\
+                   filter_by(host=host).\
+                   filter_by(topic=topic).\
+                   first()
+
+
 @require_admin_context
 def service_get_all_by_host(context, host):
     session = get_session()
@@ -1972,6 +1983,51 @@ def host_get_networks(context, host):
                        all()
 
 
+###################
+
+
+@require_admin_context
+def migration_create(context, values):
+    migration = models.Migration()
+    migration.update(values)
+    migration.save()
+    return migration
+
+
+@require_admin_context
+def migration_update(context, id, values):
+    session = get_session()
+    with session.begin():
+        migration = migration_get(context, id, session=session)
+        migration.update(values)
+        migration.save(session=session)
+        return migration
+
+
+@require_admin_context
+def migration_get(context, id, session=None):
+    if not session:
+        session = get_session()
+    result = session.query(models.Migration).\
+                     filter_by(id=id).first()
+    if not result:
+        raise exception.NotFound(_("No migration found with id %s")
+                % migration_id)
+    return result
+
+
+@require_admin_context
+def migration_get_by_instance_and_status(context, instance_id, status):
+    session = get_session()
+    result = session.query(models.Migration).\
+                     filter_by(instance_id=instance_id).\
+                     filter_by(status=status).first()
+    if not result:
+        raise exception.NotFound(_("No migration found with instance id %s")
+                % migration_id)
+    return result
+
+
 ##################
 
 

nova/db/sqlalchemy/migrate_repo/versions/009_add_instance_migrations.py

@@ -0,0 +1,61 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2010 OpenStack LLC.
+# 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.from sqlalchemy import *
+
+from sqlalchemy import *
+from migrate import *
+
+from nova import log as logging
+
+
+meta = MetaData()
+
+# Just for the ForeignKey and column creation to succeed, these are not the
+# actual definitions of instances or services.
+instances = Table('instances', meta,
+        Column('id', Integer(),  primary_key=True, nullable=False),
+        )
+
+#
+# New Tables
+#
+
+migrations = Table('migrations', meta,
+            Column('created_at', DateTime(timezone=False)),
+            Column('updated_at', DateTime(timezone=False)),
+            Column('deleted_at', DateTime(timezone=False)),
+            Column('deleted', Boolean(create_constraint=True, name=None)),
+            Column('id', Integer(), primary_key=True, nullable=False),
+            Column('source_compute', String(255)),
+            Column('dest_compute', String(255)),
+            Column('dest_host', String(255)),
+            Column('instance_id', Integer, ForeignKey('instances.id'),
+                nullable=True),
+            Column('status', String(255)),
+      )
+
+
+def upgrade(migrate_engine):
+    # Upgrade operations go here. Don't create your own engine;
+    # bind migrate_engine to your metadata
+    meta.bind = migrate_engine
+    for table in (migrations, ):
+        try:
+            table.create()
+        except Exception:
+            logging.info(repr(table))
+            logging.exception('Exception while creating table')
+            raise

nova/db/sqlalchemy/migration.py

@@ -60,7 +60,7 @@ def db_version():
                           'key_pairs', 'networks', 'projects', 'quotas',
                           'security_group_instance_association',
                           'security_group_rules', 'security_groups',
-                          'services',
+                          'services', 'migrations',
                           'users', 'user_project_association',
                           'user_project_role_association',
                           'user_role_association',

nova/db/sqlalchemy/models.py

@@ -389,6 +389,18 @@ class KeyPair(BASE, NovaBase):
     public_key = Column(Text)
 
 
+class Migration(BASE, NovaBase):
+    """Represents a running host-to-host migration."""
+    __tablename__ = 'migrations'
+    id = Column(Integer, primary_key=True, nullable=False)
+    source_compute = Column(String(255))
+    dest_compute = Column(String(255))
+    dest_host = Column(String(255))
+    instance_id = Column(Integer, ForeignKey('instances.id'), nullable=True)
+    #TODO(_cerberus_): enum
+    status = Column(String(255))
+
+
 class Network(BASE, NovaBase):
     """Represents a network."""
     __tablename__ = 'networks'
@@ -598,7 +610,7 @@ def register_models():
               Network, SecurityGroup, SecurityGroupIngressRule,
               SecurityGroupInstanceAssociation, AuthToken, User,
               Project, Certificate, ConsolePool, Console, Zone,
-              InstanceMetadata)
+              InstanceMetadata, Migration)
     engine = create_engine(FLAGS.sql_connection, echo=False)
     for model in models:
         model.metadata.create_all(engine)

nova/rpc.py

@@ -123,7 +123,7 @@ class Consumer(messaging.Consumer):
                 LOG.error(_("Reconnected to queue"))
                 self.failed_connection = False
         # NOTE(vish): This is catching all errors because we really don't
-        #             exceptions to be logged 10 times a second if some
+        #             want exceptions to be logged 10 times a second if some
         #             persistent failure occurs.
         except Exception:  # pylint: disable-msg=W0703
             if not self.failed_connection:

nova/tests/api/openstack/common.py

@@ -0,0 +1,35 @@
+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright 2011 OpenStack LLC.
+# 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.
+
+import json
+
+import webob
+
+
+def webob_factory(url):
+    """Factory for removing duplicate webob code from tests"""
+
+    base_url = url
+
+    def web_request(url, method=None, body=None):
+        req = webob.Request.blank("%s%s" % (base_url, url))
+        if method:
+            req.method = method
+        if body:
+            req.body = json.dumps(body)
+        return req
+    return web_request

nova/tests/api/openstack/test_servers.py

@@ -1,6 +1,6 @@
 # vim: tabstop=4 shiftwidth=4 softtabstop=4
 
-# Copyright 2010 OpenStack LLC.
+# Copyright 2010-2011 OpenStack LLC.
 # All Rights Reserved.
 #
 #    Licensed under the Apache License, Version 2.0 (the "License"); you may
@@ -26,10 +26,12 @@ from nova import flags
 from nova import test
 import nova.api.openstack
 from nova.api.openstack import servers
+import nova.compute.api
 import nova.db.api
 from nova.db.sqlalchemy.models import Instance
 from nova.db.sqlalchemy.models import InstanceMetadata
 import nova.rpc
+from nova.tests.api.openstack import common
 from nova.tests.api.openstack import fakes
 
 
@@ -144,6 +146,8 @@ class ServersTest(test.TestCase):
         self.stubs.Set(nova.compute.API, "get_actions", fake_compute_api)
         self.allow_admin = FLAGS.allow_admin_api
 
+        self.webreq = common.webob_factory('/v1.0/servers')
+
     def tearDown(self):
         self.stubs.UnsetAll()
         FLAGS.allow_admin_api = self.allow_admin
@@ -465,3 +469,99 @@ class ServersTest(test.TestCase):
         res = req.get_response(fakes.wsgi_app())
         self.assertEqual(res.status, '202 Accepted')
         self.assertEqual(self.server_delete_called, True)
+
+    def test_resize_server(self):
+        req = self.webreq('/1/action', 'POST', dict(resize=dict(flavorId=3)))
+
+        self.resize_called = False
+
+        def resize_mock(*args):
+            self.resize_called = True
+
+        self.stubs.Set(nova.compute.api.API, 'resize', resize_mock)
+
+        res = req.get_response(fakes.wsgi_app())
+        self.assertEqual(res.status_int, 202)
+        self.assertEqual(self.resize_called, True)
+
+    def test_resize_bad_flavor_fails(self):
+        req = self.webreq('/1/action', 'POST', dict(resize=dict(derp=3)))
+
+        self.resize_called = False
+
+        def resize_mock(*args):
+            self.resize_called = True
+
+        self.stubs.Set(nova.compute.api.API, 'resize', resize_mock)
+
+        res = req.get_response(fakes.wsgi_app())
+        self.assertEqual(res.status_int, 422)
+        self.assertEqual(self.resize_called, False)
+
+    def test_resize_raises_fails(self):
+        req = self.webreq('/1/action', 'POST', dict(resize=dict(flavorId=3)))
+
+        def resize_mock(*args):
+            raise Exception('hurr durr')
+
+        self.stubs.Set(nova.compute.api.API, 'resize', resize_mock)
+
+        res = req.get_response(fakes.wsgi_app())
+        self.assertEqual(res.status_int, 400)
+
+    def test_confirm_resize_server(self):
+        req = self.webreq('/1/action', 'POST', dict(confirmResize=None))
+
+        self.resize_called = False
+
+        def confirm_resize_mock(*args):
+            self.resize_called = True
+
+        self.stubs.Set(nova.compute.api.API, 'confirm_resize',
+                confirm_resize_mock)
+
+        res = req.get_response(fakes.wsgi_app())
+        self.assertEqual(res.status_int, 204)
+        self.assertEqual(self.resize_called, True)
+
+    def test_confirm_resize_server_fails(self):
+        req = self.webreq('/1/action', 'POST', dict(confirmResize=None))
+
+        def confirm_resize_mock(*args):
+            raise Exception('hurr durr')
+
+        self.stubs.Set(nova.compute.api.API, 'confirm_resize',
+                confirm_resize_mock)
+
+        res = req.get_response(fakes.wsgi_app())
+        self.assertEqual(res.status_int, 400)
+
+    def test_revert_resize_server(self):
+        req = self.webreq('/1/action', 'POST', dict(revertResize=None))
+
+        self.resize_called = False
+
+        def revert_resize_mock(*args):
+            self.resize_called = True
+
+        self.stubs.Set(nova.compute.api.API, 'revert_resize',
+                revert_resize_mock)
+
+        res = req.get_response(fakes.wsgi_app())
+        self.assertEqual(res.status_int, 202)
+        self.assertEqual(self.resize_called, True)
+
+    def test_revert_resize_server_fails(self):
+        req = self.webreq('/1/action', 'POST', dict(revertResize=None))
+
+        def revert_resize_mock(*args):
+            raise Exception('hurr durr')
+
+        self.stubs.Set(nova.compute.api.API, 'revert_resize',
+                revert_resize_mock)
+
+        res = req.get_response(fakes.wsgi_app())
+        self.assertEqual(res.status_int, 400)
+
+if __name__ == "__main__":
+    unittest.main()

nova/tests/test_compute.py

@@ -57,7 +57,7 @@ class ComputeTestCase(test.TestCase):
         self.manager.delete_project(self.project)
         super(ComputeTestCase, self).tearDown()
 
-    def _create_instance(self):
+    def _create_instance(self, params={}):
         """Create a test instance"""
         inst = {}
         inst['image_id'] = 'ami-test'
@@ -68,6 +68,7 @@ class ComputeTestCase(test.TestCase):
         inst['instance_type'] = 'm1.tiny'
         inst['mac_address'] = utils.generate_mac()
         inst['ami_launch_index'] = 0
+        inst.update(params)
         return db.instance_create(self.context, inst)['id']
 
     def _create_group(self):
@@ -268,9 +269,30 @@ class ComputeTestCase(test.TestCase):
 
         self.compute.terminate_instance(self.context, instance_id)
 
+    def test_resize_instance(self):
+        """Ensure instance can be migrated/resized"""
+        instance_id = self._create_instance()
+        context = self.context.elevated()
+        self.compute.run_instance(self.context, instance_id)
+        db.instance_update(self.context, instance_id, {'host': 'foo'})
+        self.compute.prep_resize(context, instance_id)
+        migration_ref = db.migration_get_by_instance_and_status(context,
+                instance_id, 'pre-migrating')
+        self.compute.resize_instance(context, instance_id,
+                migration_ref['id'])
+        self.compute.terminate_instance(context, instance_id)
+
     def test_get_by_flavor_id(self):
         type = instance_types.get_by_flavor_id(1)
         self.assertEqual(type, 'm1.tiny')
 
+    def test_resize_same_source_fails(self):
+        """Ensure instance fails to migrate when source and destination are
+        the same host"""
+        instance_id = self._create_instance()
+        self.compute.run_instance(self.context, instance_id)
+        self.assertRaises(exception.Error, self.compute.prep_resize,
+                self.context, instance_id)
+        self.compute.terminate_instance(self.context, instance_id)
         type = instance_types.get_by_flavor_id("1")
         self.assertEqual(type, 'm1.tiny')

nova/tests/test_xenapi.py

@@ -346,6 +346,44 @@ class XenAPIDiffieHellmanTestCase(test.TestCase):
         super(XenAPIDiffieHellmanTestCase, self).tearDown()
 
 
+class XenAPIMigrateInstance(test.TestCase):
+    """
+    Unit test for verifying migration-related actions
+    """
+
+    def setUp(self):
+        super(XenAPIMigrateInstance, self).setUp()
+        self.stubs = stubout.StubOutForTesting()
+        FLAGS.target_host = '127.0.0.1'
+        FLAGS.xenapi_connection_url = 'test_url'
+        FLAGS.xenapi_connection_password = 'test_pass'
+        db_fakes.stub_out_db_instance_api(self.stubs)
+        stubs.stub_out_get_target(self.stubs)
+        xenapi_fake.reset()
+        self.values = {'name': 1, 'id': 1,
+                  'project_id': 'fake',
+                  'user_id': 'fake',
+                  'image_id': 1,
+                  'kernel_id': 2,
+                  'ramdisk_id': 3,
+                  'instance_type': 'm1.large',
+                  'mac_address': 'aa:bb:cc:dd:ee:ff',
+                  }
+        stubs.stub_out_migration_methods(self.stubs)
+
+    def test_migrate_disk_and_power_off(self):
+        instance = db.instance_create(self.values)
+        stubs.stubout_session(self.stubs, stubs.FakeSessionForMigrationTests)
+        conn = xenapi_conn.get_connection(False)
+        conn.migrate_disk_and_power_off(instance, '127.0.0.1')
+
+    def test_attach_disk(self):
+        instance = db.instance_create(self.values)
+        stubs.stubout_session(self.stubs, stubs.FakeSessionForMigrationTests)
+        conn = xenapi_conn.get_connection(False)
+        conn.attach_disk(instance, {'base_copy': 'hurr', 'cow': 'durr'})
+
+
 class XenAPIDetermineDiskImageTestCase(test.TestCase):
     """
     Unit tests for code that detects the ImageType

nova/tests/xenapi/stubs.py

@@ -20,6 +20,7 @@ from nova.virt import xenapi_conn
 from nova.virt.xenapi import fake
 from nova.virt.xenapi import volume_utils
 from nova.virt.xenapi import vm_utils
+from nova.virt.xenapi import vmops
 
 
 def stubout_instance_snapshot(stubs):
@@ -217,3 +218,44 @@ class FakeSessionForVolumeFailedTests(FakeSessionForVolumeTests):
 
     def SR_forget(self, _1, ref):
         pass
+
+
+class FakeSessionForMigrationTests(fake.SessionBase):
+    """Stubs out a XenAPISession for Migration tests"""
+    def __init__(self, uri):
+        super(FakeSessionForMigrationTests, self).__init__(uri)
+
+
+def stub_out_migration_methods(stubs):
+    def fake_get_snapshot(self, instance):
+        return 'foo', 'bar'
+
+    @classmethod
+    def fake_get_vdi(cls, session, vm_ref):
+        vdi_ref = fake.create_vdi(name_label='derp', read_only=False,
+                             sr_ref='herp', sharable=False)
+        vdi_rec = session.get_xenapi().VDI.get_record(vdi_ref)
+        return vdi_ref, {'uuid': vdi_rec['uuid'], }
+
+    def fake_shutdown(self, inst, vm, method='clean'):
+        pass
+
+    @classmethod
+    def fake_sr(cls, session, *args):
+        pass
+
+    @classmethod
+    def fake_get_sr_path(cls, *args):
+        return "fake"
+
+    def fake_destroy(*args, **kwargs):
+        pass
+
+    stubs.Set(vmops.VMOps, '_destroy', fake_destroy)
+    stubs.Set(vm_utils.VMHelper, 'scan_default_sr', fake_sr)
+    stubs.Set(vm_utils.VMHelper, 'scan_sr', fake_sr)
+    stubs.Set(vmops.VMOps, '_get_snapshot', fake_get_snapshot)
+    stubs.Set(vm_utils.VMHelper, 'get_vdi_for_vm_safely', fake_get_vdi)
+    stubs.Set(xenapi_conn.XenAPISession, 'wait_for_task', lambda x, y, z: None)
+    stubs.Set(vm_utils.VMHelper, 'get_sr_path', fake_get_sr_path)
+    stubs.Set(vmops.VMOps, '_shutdown', fake_shutdown)

nova/virt/fake.py

@@ -139,6 +139,24 @@ class FakeConnection(object):
         """
         pass
 
+    def get_host_ip_addr(self):
+        """
+        Retrieves the IP address of the dom0
+        """
+        pass
+
+    def resize(self, instance, flavor):
+        """
+        Resizes/Migrates the specified instance.
+
+        The flavor parameter determines whether or not the instance RAM and
+        disk space are modified, and if so, to what size.
+
+        The work will be done asynchronously. This function returns a task
+        that allows the caller to detect when it is complete.
+        """
+        pass
+
     def set_admin_password(self, instance, new_pass):
         """
         Set the root password on the specified instance.
@@ -179,6 +197,19 @@ class FakeConnection(object):
         """
         pass
 
+    def migrate_disk_and_power_off(self, instance, dest):
+        """
+        Transfers the disk of a running instance in multiple phases, turning
+        off the instance before the end.
+        """
+        pass
+
+    def attach_disk(self, instance, disk_info):
+        """
+        Attaches the disk to an instance given the metadata disk_info
+        """
+        pass
+
     def pause(self, instance, callback):
         """
         Pause the specified instance.

nova/virt/xenapi/fake.py

@@ -290,6 +290,9 @@ class SessionBase(object):
         #Always return 12GB available
         return 12 * 1024 * 1024 * 1024
 
+    def host_call_plugin(*args):
+        return 'herp'
+
     def xenapi_request(self, methodname, params):
         if methodname.startswith('login'):
             self._login(methodname, params)

nova/virt/xenapi/vm_utils.py

@@ -252,17 +252,32 @@ class VMHelper(HelperBase):
                 % locals())
         return vdi_ref
 
+    @classmethod
+    def get_vdi_for_vm_safely(cls, session, vm_ref):
+        vdi_refs = VMHelper.lookup_vm_vdis(session, vm_ref)
+        if vdi_refs is None:
+            raise Exception(_("No VDIs found for VM %s") % vm_ref)
+        else:
+            num_vdis = len(vdi_refs)
+            if num_vdis != 1:
+                raise Exception(
+                        _("Unexpected number of VDIs (%(num_vdis)s) found"
+                        " for VM %(vm_ref)s") % locals())
+
+        vdi_ref = vdi_refs[0]
+        vdi_rec = session.get_xenapi().VDI.get_record(vdi_ref)
+        return vdi_ref, vdi_rec
+
     @classmethod
     def create_snapshot(cls, session, instance_id, vm_ref, label):
-        """ Creates Snapshot (Template) VM, Snapshot VBD, Snapshot VDI,
-        Snapshot VHD
-        """
+        """Creates Snapshot (Template) VM, Snapshot VBD, Snapshot VDI,
+        Snapshot VHD"""
         #TODO(sirp): Add quiesce and VSS locking support when Windows support
         # is added
         LOG.debug(_("Snapshotting VM %(vm_ref)s with label '%(label)s'...")
                 % locals())
 
-        vm_vdi_ref, vm_vdi_rec = get_vdi_for_vm_safely(session, vm_ref)
+        vm_vdi_ref, vm_vdi_rec = cls.get_vdi_for_vm_safely(session, vm_ref)
         vm_vdi_uuid = vm_vdi_rec["uuid"]
         sr_ref = vm_vdi_rec["SR"]
 
@@ -270,7 +285,8 @@ class VMHelper(HelperBase):
 
         task = session.call_xenapi('Async.VM.snapshot', vm_ref, label)
         template_vm_ref = session.wait_for_task(task, instance_id)
-        template_vdi_rec = get_vdi_for_vm_safely(session, template_vm_ref)[1]
+        template_vdi_rec = cls.get_vdi_for_vm_safely(session,
+                template_vm_ref)[1]
         template_vdi_uuid = template_vdi_rec["uuid"]
 
         LOG.debug(_('Created snapshot %(template_vm_ref)s from'
@@ -284,6 +300,24 @@ class VMHelper(HelperBase):
                               'snap': template_vdi_uuid}
         return template_vm_ref, template_vdi_uuids
 
+    @classmethod
+    def get_sr(cls, session, sr_label='slices'):
+        """Finds the SR named by the given name label and returns
+        the UUID"""
+        return session.call_xenapi('SR.get_by_name_label', sr_label)[0]
+
+    @classmethod
+    def get_sr_path(cls, session):
+        """Return the path to our storage repository
+
+        This is used when we're dealing with VHDs directly, either by taking
+        snapshots or by restoring an image in the DISK_VHD format.
+        """
+        sr_ref = safe_find_sr(session)
+        sr_rec = session.get_xenapi().SR.get_record(sr_ref)
+        sr_uuid = sr_rec["uuid"]
+        return os.path.join(FLAGS.xenapi_sr_base_path, sr_uuid)
+
     @classmethod
     def upload_image(cls, session, instance_id, vdi_uuids, image_id):
         """ Requests that the Glance plugin bundle the specified VDIs and
@@ -298,7 +332,7 @@ class VMHelper(HelperBase):
                   'image_id': image_id,
                   'glance_host': FLAGS.glance_host,
                   'glance_port': FLAGS.glance_port,
-                  'sr_path': get_sr_path(session)}
+                  'sr_path': cls.get_sr_path(session)}
 
         kwargs = {'params': pickle.dumps(params)}
         task = session.async_call_plugin('glance', 'upload_vhd', kwargs)
@@ -341,13 +375,13 @@ class VMHelper(HelperBase):
                   'glance_host': FLAGS.glance_host,
                   'glance_port': FLAGS.glance_port,
                   'uuid_stack': uuid_stack,
-                  'sr_path': get_sr_path(session)}
+                  'sr_path': cls.get_sr_path(session)}
 
         kwargs = {'params': pickle.dumps(params)}
         task = session.async_call_plugin('glance', 'download_vhd', kwargs)
         vdi_uuid = session.wait_for_task(task, instance_id)
 
-        scan_sr(session, instance_id, sr_ref)
+        cls.scan_sr(session, instance_id, sr_ref)
 
         # Set the name-label to ease debugging
         vdi_ref = session.get_xenapi().VDI.get_by_uuid(vdi_uuid)
@@ -609,6 +643,21 @@ class VMHelper(HelperBase):
         except cls.XenAPI.Failure as e:
             return {"Unable to retrieve diagnostics": e}
 
+    @classmethod
+    def scan_sr(cls, session, instance_id=None, sr_ref=None):
+        """Scans the SR specified by sr_ref"""
+        if sr_ref:
+            LOG.debug(_("Re-scanning SR %s"), sr_ref)
+            task = session.call_xenapi('Async.SR.scan', sr_ref)
+            session.wait_for_task(task, instance_id)
+
+    @classmethod
+    def scan_default_sr(cls, session):
+        """Looks for the system default SR and triggers a re-scan"""
+        #FIXME(sirp/mdietz): refactor scan_default_sr in there
+        sr_ref = cls.get_sr(session)
+        session.call_xenapi('SR.scan', sr_ref)
+
 
 def get_rrd(host, uuid):
     """Return the VM RRD XML as a string"""
@@ -651,12 +700,6 @@ def get_vhd_parent_uuid(session, vdi_ref):
         return None
 
 
-def scan_sr(session, instance_id, sr_ref):
-    LOG.debug(_("Re-scanning SR %s"), sr_ref)
-    task = session.call_xenapi('Async.SR.scan', sr_ref)
-    session.wait_for_task(task, instance_id)
-
-
 def wait_for_vhd_coalesce(session, instance_id, sr_ref, vdi_ref,
                           original_parent_uuid):
     """ Spin until the parent VHD is coalesced into its parent VHD
@@ -681,7 +724,7 @@ def wait_for_vhd_coalesce(session, instance_id, sr_ref, vdi_ref,
                     " %(max_attempts)d), giving up...") % locals())
             raise exception.Error(msg)
 
-        scan_sr(session, instance_id, sr_ref)
+        VMHelper.scan_sr(session, instance_id, sr_ref)
         parent_uuid = get_vhd_parent_uuid(session, vdi_ref)
         if original_parent_uuid and (parent_uuid != original_parent_uuid):
             LOG.debug(_("Parent %(parent_uuid)s doesn't match original parent"
@@ -738,18 +781,6 @@ def find_sr(session):
     return None
 
 
-def get_sr_path(session):
-    """Return the path to our storage repository
-
-    This is used when we're dealing with VHDs directly, either by taking
-    snapshots or by restoring an image in the DISK_VHD format.
-    """
-    sr_ref = safe_find_sr(session)
-    sr_rec = session.get_xenapi().SR.get_record(sr_ref)
-    sr_uuid = sr_rec["uuid"]
-    return os.path.join(FLAGS.xenapi_sr_base_path, sr_uuid)
-
-
 def remap_vbd_dev(dev):
     """Return the appropriate location for a plugged-in VBD device
 

nova/virt/xenapi/vmops.py

@@ -22,6 +22,7 @@ Management class for VM-related functions (spawn, reboot, etc).
 import json
 import M2Crypto
 import os
+import pickle
 import subprocess
 import tempfile
 import uuid
@@ -61,7 +62,17 @@ class VMOps(object):
                 vms.append(rec["name_label"])
         return vms
 
-    def spawn(self, instance):
+    def _start(self, instance, vm_ref=None):
+        """Power on a VM instance"""
+        if not vm_ref:
+            vm_ref = VMHelper.lookup(self._session, instance.name)
+        if vm_ref is None:
+            raise exception(_('Attempted to power on non-existent instance'
+            ' bad instance id %s') % instance.id)
+        LOG.debug(_("Starting instance %s"), instance.name)
+        self._session.call_xenapi('VM.start', vm_ref, False, False)
+
+    def spawn(self, instance, disk):
         """Create VM instance"""
         instance_name = instance.name
         vm = VMHelper.lookup(self._session, instance_name)
@@ -81,16 +92,22 @@ class VMOps(object):
         user = AuthManager().get_user(instance.user_id)
         project = AuthManager().get_project(instance.project_id)
 
-        disk_image_type = VMHelper.determine_disk_image_type(instance)
+        vdi_ref = kernel = ramdisk = pv_kernel = None
 
-        vdi_uuid = VMHelper.fetch_image(self._session, instance.id,
-            instance.image_id, user, project, disk_image_type)
+        # Are we building from a pre-existing disk?
+        if not disk:
+            #if kernel is not present we must download a raw disk
 
-        vdi_ref = self._session.call_xenapi('VDI.get_by_uuid', vdi_uuid)
+            disk_image_type = VMHelper.determine_disk_image_type(instance)
+            vdi_uuid = VMHelper.fetch_image(self._session, instance.id,
+                    instance.image_id, user, project, disk_image_type)
+            vdi_ref = self._session.call_xenapi('VDI.get_by_uuid', vdi_uuid)
+
+        else:
+            vdi_ref = self._session.call_xenapi('VDI.get_by_uuid', disk)
 
-        pv_kernel = False
         if disk_image_type == ImageType.DISK_RAW:
-            #Have a look at the VDI and see if it has a PV kernel
+            # Have a look at the VDI and see if it has a PV kernel
             pv_kernel = VMHelper.lookup_image(self._session, instance.id,
                                               vdi_ref)
         elif disk_image_type == ImageType.DISK_VHD:
@@ -98,19 +115,18 @@ class VMOps(object):
             # configurable as Windows will use HVM.
             pv_kernel = True
 
-        kernel = None
         if instance.kernel_id:
             kernel = VMHelper.fetch_image(self._session, instance.id,
                 instance.kernel_id, user, project, ImageType.KERNEL_RAMDISK)
 
-        ramdisk = None
         if instance.ramdisk_id:
             ramdisk = VMHelper.fetch_image(self._session, instance.id,
                 instance.ramdisk_id, user, project, ImageType.KERNEL_RAMDISK)
 
         vm_ref = VMHelper.create_vm(self._session,
                                           instance, kernel, ramdisk, pv_kernel)
-        VMHelper.create_vbd(self._session, vm_ref, vdi_ref, 0, True)
+        VMHelper.create_vbd(session=self._session, vm_ref=vm_ref,
+                vdi_ref=vdi_ref, userdevice=0, bootable=True)
 
         # inject_network_info and create vifs
         networks = self.inject_network_info(instance)
@@ -217,7 +233,7 @@ class VMOps(object):
             "start")
 
     def snapshot(self, instance, image_id):
-        """ Create snapshot from a running VM instance
+        """Create snapshot from a running VM instance
 
         :param instance: instance to be snapshotted
         :param image_id: id of image to upload to
@@ -238,7 +254,20 @@ class VMOps(object):
             that will bundle the VHDs together and then push the bundle into
             Glance.
         """
+        template_vm_ref = None
+        try:
+            template_vm_ref, template_vdi_uuids = self._get_snapshot(instance)
+            # call plugin to ship snapshot off to glance
+            VMHelper.upload_image(
+                    self._session, instance.id, template_vdi_uuids, image_id)
+        finally:
+            if template_vm_ref:
+                self._destroy(instance, template_vm_ref,
+                        shutdown=False, destroy_kernel_ramdisk=False)
 
+        logging.debug(_("Finished snapshot and upload for VM %s"), instance)
+
+    def _get_snapshot(self, instance):
         #TODO(sirp): Add quiesce and VSS locking support when Windows support
         # is added
 
@@ -249,20 +278,89 @@ class VMOps(object):
         try:
             template_vm_ref, template_vdi_uuids = VMHelper.create_snapshot(
                 self._session, instance.id, vm_ref, label)
+            return template_vm_ref, template_vdi_uuids
         except self.XenAPI.Failure, exc:
             logging.error(_("Unable to Snapshot %(vm_ref)s: %(exc)s")
                     % locals())
             return
 
-        try:
-            # call plugin to ship snapshot off to glance
-            VMHelper.upload_image(
-                self._session, instance.id, template_vdi_uuids, image_id)
-        finally:
-            self._destroy(instance, template_vm_ref, shutdown=False,
-                          destroy_kernel_ramdisk=False)
+    def migrate_disk_and_power_off(self, instance, dest):
+        """Copies a VHD from one host machine to another
 
-        logging.debug(_("Finished snapshot and upload for VM %s"), instance)
+        :param instance: the instance that owns the VHD in question
+        :param dest: the destination host machine
+        :param disk_type: values are 'primary' or 'cow'
+        """
+        vm_ref = VMHelper.lookup(self._session, instance.name)
+
+        # The primary VDI becomes the COW after the snapshot, and we can
+        # identify it via the VBD. The base copy is the parent_uuid returned
+        # from the snapshot creation
+
+        base_copy_uuid = cow_uuid = None
+        template_vdi_uuids = template_vm_ref = None
+        try:
+            # transfer the base copy
+            template_vm_ref, template_vdi_uuids = self._get_snapshot(instance)
+            base_copy_uuid = template_vdi_uuids[1]
+            vdi_ref, vm_vdi_rec = \
+                    VMHelper.get_vdi_for_vm_safely(self._session, vm_ref)
+            cow_uuid = vm_vdi_rec['uuid']
+
+            params = {'host': dest,
+                      'vdi_uuid': base_copy_uuid,
+                      'instance_id': instance.id,
+                      'sr_path': VMHelper.get_sr_path(self._session)}
+
+            task = self._session.async_call_plugin('migration', 'transfer_vhd',
+                    {'params': pickle.dumps(params)})
+            self._session.wait_for_task(task, instance.id)
+
+            # Now power down the instance and transfer the COW VHD
+            self._shutdown(instance, vm_ref, method='clean')
+
+            params = {'host': dest,
+                      'vdi_uuid': cow_uuid,
+                      'instance_id': instance.id,
+                      'sr_path': VMHelper.get_sr_path(self._session), }
+
+            task = self._session.async_call_plugin('migration', 'transfer_vhd',
+                    {'params': pickle.dumps(params)})
+            self._session.wait_for_task(task, instance.id)
+
+        finally:
+            if template_vm_ref:
+                self._destroy(instance, template_vm_ref,
+                        shutdown=False, destroy_kernel_ramdisk=False)
+
+        # TODO(mdietz): we could also consider renaming these to something
+        # sensible so we don't need to blindly pass around dictionaries
+        return {'base_copy': base_copy_uuid, 'cow': cow_uuid}
+
+    def attach_disk(self, instance, disk_info):
+        """Links the base copy VHD to the COW via the XAPI plugin"""
+        vm_ref = VMHelper.lookup(self._session, instance.name)
+        new_base_copy_uuid = str(uuid.uuid4())
+        new_cow_uuid = str(uuid.uuid4())
+        params = {'instance_id': instance.id,
+                  'old_base_copy_uuid': disk_info['base_copy'],
+                  'old_cow_uuid': disk_info['cow'],
+                  'new_base_copy_uuid': new_base_copy_uuid,
+                  'new_cow_uuid': new_cow_uuid,
+                  'sr_path': VMHelper.get_sr_path(self._session), }
+
+        task = self._session.async_call_plugin('migration',
+                'move_vhds_into_sr', {'params': pickle.dumps(params)})
+        self._session.wait_for_task(task, instance.id)
+
+        # Now we rescan the SR so we find the VHDs
+        VMHelper.scan_default_sr(self._session)
+
+        return new_cow_uuid
+
+    def resize(self, instance, flavor):
+        """Resize a running instance by changing it's RAM and disk size """
+        raise NotImplementedError()
 
     def reboot(self, instance):
         """Reboot VM instance"""
@@ -308,11 +406,6 @@ class VMOps(object):
             raise RuntimeError(resp_dict['message'])
         return resp_dict['message']
 
-    def _start(self, instance, vm):
-        """Start an instance"""
-        task = self._session.call_xenapi("Async.VM.start", vm, False, False)
-        self._session.wait_for_task(task, instance.id)
-
     def inject_file(self, instance, b64_path, b64_contents):
         """Write a file to the VM instance. The path to which it is to be
         written and the contents of the file need to be supplied; both should
@@ -355,8 +448,7 @@ class VMOps(object):
             if hard:
                 task = self._session.call_xenapi("Async.VM.hard_shutdown", vm)
             else:
-                task = self._session.call_xenapi("Async.VM.clean_shutdown", vm)
-
+                task = self._session.call_xenapi('Async.VM.clean_shutdown', vm)
             self._session.wait_for_task(task, instance.id)
         except self.XenAPI.Failure, exc:
             LOG.exception(exc)

nova/virt/xenapi_conn.py

@@ -154,14 +154,18 @@ class XenAPIConnection(object):
         """List VM instances"""
         return self._vmops.list_instances()
 
-    def spawn(self, instance):
+    def spawn(self, instance, disk=None):
         """Create VM instance"""
-        self._vmops.spawn(instance)
+        self._vmops.spawn(instance, disk)
 
     def snapshot(self, instance, image_id):
         """ Create snapshot from a running VM instance """
         self._vmops.snapshot(instance, image_id)
 
+    def resize(self, instance, flavor):
+        """Resize a VM instance"""
+        raise NotImplementedError()
+
     def reboot(self, instance):
         """Reboot VM instance"""
         self._vmops.reboot(instance)
@@ -188,6 +192,15 @@ class XenAPIConnection(object):
         """Unpause paused VM instance"""
         self._vmops.unpause(instance, callback)
 
+    def migrate_disk_and_power_off(self, instance, dest):
+        """Transfers the VHD of a running instance to another host, then shuts
+        off the instance copies over the COW disk"""
+        return self._vmops.migrate_disk_and_power_off(instance, dest)
+
+    def attach_disk(self, instance, disk_info):
+        """Moves the copied VDIs into the SR"""
+        return self._vmops.attach_disk(instance, disk_info)
+
     def suspend(self, instance, callback):
         """suspend the specified instance"""
         self._vmops.suspend(instance, callback)
@@ -228,6 +241,10 @@ class XenAPIConnection(object):
         """Return link to instance's ajax console"""
         return self._vmops.get_ajax_console(instance)
 
+    def get_host_ip_addr(self):
+        xs_url = urlparse.urlparse(FLAGS.xenapi_connection_url)
+        return xs_url.netloc
+
     def attach_volume(self, instance_name, device_path, mountpoint):
         """Attach volume storage to VM instance"""
         return self._volumeops.attach_volume(instance_name,

plugins/xenserver/xenapi/etc/xapi.d/plugins/migration

@@ -0,0 +1,117 @@
+#!/usr/bin/env python
+
+# Copyright 2010 OpenStack LLC.
+# 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.
+
+"""
+XenAPI Plugin for transfering data between host nodes
+"""
+
+import os
+import os.path
+import pickle
+import shutil
+import subprocess
+
+import XenAPIPlugin
+
+from pluginlib_nova import *
+configure_logging('migration')
+
+
+def move_vhds_into_sr(session, args):
+    """Moves the VHDs from their copied location to the SR"""
+    params = pickle.loads(exists(args, 'params'))
+    instance_id = params['instance_id']
+
+    old_base_copy_uuid = params['old_base_copy_uuid']
+    old_cow_uuid = params['old_cow_uuid']
+
+    new_base_copy_uuid = params['new_base_copy_uuid']
+    new_cow_uuid = params['new_cow_uuid']
+
+    sr_path = params['sr_path']
+    sr_temp_path = "%s/images/" % sr_path
+
+    # Discover the copied VHDs locally, and then set up paths to copy
+    # them to under the SR
+    source_image_path = "%s/instance%d" % ('/images/', instance_id)
+    source_base_copy_path = "%s/%s.vhd" % (source_image_path,
+            old_base_copy_uuid)
+    source_cow_path = "%s/%s.vhd" % (source_image_path, old_cow_uuid)
+
+    temp_vhd_path = "%s/instance%d/" % (sr_temp_path, instance_id)
+    new_base_copy_path = "%s/%s.vhd" % (temp_vhd_path, new_base_copy_uuid)
+    new_cow_path = "%s/%s.vhd" % (temp_vhd_path, new_cow_uuid)
+
+    logging.debug('Creating temporary SR path %s' % temp_vhd_path)
+    os.makedirs(temp_vhd_path)
+
+    logging.debug('Moving %s into %s' % (source_base_copy_path, temp_vhd_path))
+    shutil.move(source_base_copy_path, new_base_copy_path)
+
+    logging.debug('Moving %s into %s' % (source_cow_path, temp_vhd_path))
+    shutil.move(source_cow_path, new_cow_path)
+
+    logging.debug('Cleaning up %s' % source_image_path)
+    os.rmdir(source_image_path)
+
+    # Link the COW to the base copy
+    logging.debug('Attaching COW to the base copy %s -> %s' %
+            (new_cow_path, new_base_copy_path))
+    subprocess.call(shlex.split('/usr/sbin/vhd-util modify -n %s -p %s' %
+            (new_cow_path, new_base_copy_path)))
+    logging.debug('Moving VHDs into SR %s' % sr_path)
+    shutil.move("%s/%s.vhd" % (temp_vhd_path, new_base_copy_uuid), sr_path)
+    shutil.move("%s/%s.vhd" % (temp_vhd_path, new_cow_uuid), sr_path)
+
+    logging.debug('Cleaning up temporary SR path %s' % temp_vhd_path)
+    os.rmdir(temp_vhd_path)
+    return ""
+
+
+def transfer_vhd(session, args):
+    """Rsyncs a VHD to an adjacent host"""
+    params = pickle.loads(exists(args, 'params'))
+    instance_id = params['instance_id']
+    host = params['host']
+    vdi_uuid = params['vdi_uuid']
+    sr_path = params['sr_path']
+    vhd_path = "%s.vhd" % vdi_uuid
+
+    source_path = "%s/%s" % (sr_path, vhd_path)
+    dest_path = '%s:%sinstance%d/' % (host, '/images/', instance_id)
+
+    logging.debug("Preparing to transmit %s to %s" % (source_path,
+            dest_path))
+
+    ssh_cmd = 'ssh -o StrictHostKeyChecking=no'
+
+    rsync_args = shlex.split('nohup /usr/bin/rsync -av --progress -e %s %s %s'
+            % (ssh_cmd, source_path, dest_path))
+
+    logging.debug('rsync %s' % (' '.join(rsync_args, )))
+
+    rsync_proc = subprocess.Popen(rsync_args, stdout=subprocess.PIPE)
+    logging.debug('Rsync output: \n %s' % rsync_proc.communicate()[0])
+    logging.debug('Rsync return: %d' % rsync_proc.returncode)
+    if rsync_proc.returncode != 0:
+        raise Exception("Unexpected VHD transfer failure")
+    return ""
+
+
+if __name__ == '__main__':
+    XenAPIPlugin.dispatch({'transfer_vhd': transfer_vhd,
+            'move_vhds_into_sr': move_vhds_into_sr, })