pull-up from trunk

19 files changed, 665 insertions, 103 deletions

diff --git a/nova/api/openstack/contrib/hosts.py b/nova/api/openstack/contrib/hosts.py
new file mode 100644
index 000000000..55e57e1a4
--- /dev/null
+++ b/nova/api/openstack/contrib/hosts.py
@@ -0,0 +1,114 @@
+# Copyright (c) 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.
+
+"""The hosts admin extension."""
+
+import webob.exc
+
+from nova import compute
+from nova import exception
+from nova import flags
+from nova import log as logging
+from nova.api.openstack import common
+from nova.api.openstack import extensions
+from nova.api.openstack import faults
+from nova.scheduler import api as scheduler_api
+
+
+LOG = logging.getLogger("nova.api.hosts")
+FLAGS = flags.FLAGS
+
+
+def _list_hosts(req, service=None):
+    """Returns a summary list of hosts, optionally filtering
+    by service type.
+    """
+    context = req.environ['nova.context']
+    hosts = scheduler_api.get_host_list(context)
+    if service:
+        hosts = [host for host in hosts
+                if host["service"] == service]
+    return hosts
+
+
+def check_host(fn):
+    """Makes sure that the host exists."""
+    def wrapped(self, req, id, service=None, *args, **kwargs):
+        listed_hosts = _list_hosts(req, service)
+        hosts = [h["host_name"] for h in listed_hosts]
+        if id in hosts:
+            return fn(self, req, id, *args, **kwargs)
+        else:
+            raise exception.HostNotFound(host=id)
+    return wrapped
+
+
+class HostController(object):
+    """The Hosts API controller for the OpenStack API."""
+    def __init__(self):
+        self.compute_api = compute.API()
+        super(HostController, self).__init__()
+
+    def index(self, req):
+        return {'hosts': _list_hosts(req)}
+
+    @check_host
+    def update(self, req, id, body):
+        for raw_key, raw_val in body.iteritems():
+            key = raw_key.lower().strip()
+            val = raw_val.lower().strip()
+            # NOTE: (dabo) Right now only 'status' can be set, but other
+            # actions may follow.
+            if key == "status":
+                if val[:6] in ("enable", "disabl"):
+                    return self._set_enabled_status(req, id,
+                            enabled=(val.startswith("enable")))
+                else:
+                    explanation = _("Invalid status: '%s'") % raw_val
+                    raise webob.exc.HTTPBadRequest(explanation=explanation)
+            else:
+                explanation = _("Invalid update setting: '%s'") % raw_key
+                raise webob.exc.HTTPBadRequest(explanation=explanation)
+
+    def _set_enabled_status(self, req, host, enabled):
+        """Sets the specified host's ability to accept new instances."""
+        context = req.environ['nova.context']
+        state = "enabled" if enabled else "disabled"
+        LOG.audit(_("Setting host %(host)s to %(state)s.") % locals())
+        result = self.compute_api.set_host_enabled(context, host=host,
+                enabled=enabled)
+        return {"host": host, "status": result}
+
+
+class Hosts(extensions.ExtensionDescriptor):
+    def get_name(self):
+        return "Hosts"
+
+    def get_alias(self):
+        return "os-hosts"
+
+    def get_description(self):
+        return "Host administration"
+
+    def get_namespace(self):
+        return "http://docs.openstack.org/ext/hosts/api/v1.1"
+
+    def get_updated(self):
+        return "2011-06-29T00:00:00+00:00"
+
+    def get_resources(self):
+        resources = [extensions.ResourceExtension('os-hosts', HostController(),
+                collection_actions={'update': 'PUT'}, member_actions={})]
+        return resources
diff --git a/nova/compute/api.py b/nova/compute/api.py
index 28459dc75..b0eedcd64 100644
--- a/nova/compute/api.py
+++ b/nova/compute/api.py
@@ -912,6 +912,11 @@ class API(base.Base):
         """Unpause the given instance."""
         self._cast_compute_message('unpause_instance', context, instance_id)
 
+    def set_host_enabled(self, context, host, enabled):
+        """Sets the specified host's ability to accept new instances."""
+        return self._call_compute_message("set_host_enabled", context,
+                instance_id=None, host=host, params={"enabled": enabled})
+
     @scheduler_api.reroute_compute("diagnostics")
     def get_diagnostics(self, context, instance_id):
         """Retrieve diagnostics for the given instance."""
diff --git a/nova/compute/manager.py b/nova/compute/manager.py
index bbbddde0a..91a604934 100644
--- a/nova/compute/manager.py
+++ b/nova/compute/manager.py
@@ -875,6 +875,12 @@ class ComputeManager(manager.SchedulerDependentManager):
                                                        result))
 
     @exception.wrap_exception
+    def set_host_enabled(self, context, instance_id=None, host=None,
+            enabled=None):
+        """Sets the specified host's ability to accept new instances."""
+        return self.driver.set_host_enabled(host, enabled)
+
+    @exception.wrap_exception
     def get_diagnostics(self, context, instance_id):
         """Retrieve diagnostics for an instance on this host."""
         instance_ref = self.db.instance_get(context, instance_id)
diff --git a/nova/scheduler/api.py b/nova/scheduler/api.py
index 0f4fc48c8..137b671c0 100644
--- a/nova/scheduler/api.py
+++ b/nova/scheduler/api.py
@@ -51,6 +51,11 @@ def _call_scheduler(method, context, params=None):
     return rpc.call(context, queue, kwargs)
 
 
+def get_host_list(context):
+    """Return a list of hosts associated with this zone."""
+    return _call_scheduler('get_host_list', context)
+
+
 def get_zone_list(context):
     """Return a list of zones assoicated with this zone."""
     items = _call_scheduler('get_zone_list', context)
diff --git a/nova/scheduler/manager.py b/nova/scheduler/manager.py
index 6cb75aa8d..749d66cad 100644
--- a/nova/scheduler/manager.py
+++ b/nova/scheduler/manager.py
@@ -56,6 +56,10 @@ class SchedulerManager(manager.Manager):
         """Poll child zones periodically to get status."""
         self.zone_manager.ping(context)
 
+    def get_host_list(self, context=None):
+        """Get a list of hosts from the ZoneManager."""
+        return self.zone_manager.get_host_list()
+
     def get_zone_list(self, context=None):
         """Get a list of zones from the ZoneManager."""
         return self.zone_manager.get_zone_list()
diff --git a/nova/scheduler/zone_manager.py b/nova/scheduler/zone_manager.py
index ba7403c15..6093443a9 100644
--- a/nova/scheduler/zone_manager.py
+++ b/nova/scheduler/zone_manager.py
@@ -115,6 +115,18 @@ class ZoneManager(object):
         """Return the list of zones we know about."""
         return [zone.to_dict() for zone in self.zone_states.values()]
 
+    def get_host_list(self):
+        """Returns a list of dicts for each host that the Zone Manager
+        knows about. Each dict contains the host_name and the service
+        for that host.
+        """
+        all_hosts = self.service_states.keys()
+        ret = []
+        for host in self.service_states:
+            for svc in self.service_states[host]:
+                ret.append({"service": svc, "host_name": host})
+        return ret
+
     def get_zone_capabilities(self, context):
         """Roll up all the individual host info to generic 'service'
            capabilities. Each capability is aggregated into
@@ -127,13 +139,15 @@ class ZoneManager(object):
         combined = {}  # { <service>_<cap> : (min, max), ... }
         for host, host_dict in hosts_dict.iteritems():
             for service_name, service_dict in host_dict.iteritems():
+                if not service_dict.get("enabled", True):
+                    # Service is disabled; do no include it
+                    continue
                 for cap, value in service_dict.iteritems():
                     key = "%s_%s" % (service_name, cap)
                     min_value, max_value = combined.get(key, (value, value))
                     min_value = min(min_value, value)
                     max_value = max(max_value, value)
                     combined[key] = (min_value, max_value)
-
         return combined
 
     def _refresh_from_db(self, context):
diff --git a/nova/tests/test_hosts.py b/nova/tests/test_hosts.py
new file mode 100644
index 000000000..548f81f8b
--- /dev/null
+++ b/nova/tests/test_hosts.py
@@ -0,0 +1,102 @@
+# Copyright (c) 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 stubout
+import webob.exc
+
+from nova import context
+from nova import exception
+from nova import flags
+from nova import log as logging
+from nova import test
+from nova.api.openstack.contrib import hosts as os_hosts
+from nova.scheduler import api as scheduler_api
+
+
+FLAGS = flags.FLAGS
+LOG = logging.getLogger('nova.tests.hosts')
+# Simulate the hosts returned by the zone manager.
+HOST_LIST = [
+        {"host_name": "host_c1", "service": "compute"},
+        {"host_name": "host_c2", "service": "compute"},
+        {"host_name": "host_v1", "service": "volume"},
+        {"host_name": "host_v2", "service": "volume"}]
+
+
+def stub_get_host_list(req):
+    return HOST_LIST
+
+
+def stub_set_host_enabled(context, host, enabled):
+    # We'll simulate success and failure by assuming
+    # that 'host_c1' always succeeds, and 'host_c2'
+    # always fails
+    fail = (host == "host_c2")
+    status = "enabled" if (enabled ^ fail) else "disabled"
+    return status
+
+
+class FakeRequest(object):
+    environ = {"nova.context": context.get_admin_context()}
+
+
+class HostTestCase(test.TestCase):
+    """Test Case for hosts."""
+
+    def setUp(self):
+        super(HostTestCase, self).setUp()
+        self.controller = os_hosts.HostController()
+        self.req = FakeRequest()
+        self.stubs.Set(scheduler_api, 'get_host_list', stub_get_host_list)
+        self.stubs.Set(self.controller.compute_api, 'set_host_enabled',
+                stub_set_host_enabled)
+
+    def test_list_hosts(self):
+        """Verify that the compute hosts are returned."""
+        hosts = os_hosts._list_hosts(self.req)
+        self.assertEqual(hosts, HOST_LIST)
+
+        compute_hosts = os_hosts._list_hosts(self.req, "compute")
+        expected = [host for host in HOST_LIST
+                if host["service"] == "compute"]
+        self.assertEqual(compute_hosts, expected)
+
+    def test_disable_host(self):
+        dis_body = {"status": "disable"}
+        result_c1 = self.controller.update(self.req, "host_c1", body=dis_body)
+        self.assertEqual(result_c1["status"], "disabled")
+        result_c2 = self.controller.update(self.req, "host_c2", body=dis_body)
+        self.assertEqual(result_c2["status"], "enabled")
+
+    def test_enable_host(self):
+        en_body = {"status": "enable"}
+        result_c1 = self.controller.update(self.req, "host_c1", body=en_body)
+        self.assertEqual(result_c1["status"], "enabled")
+        result_c2 = self.controller.update(self.req, "host_c2", body=en_body)
+        self.assertEqual(result_c2["status"], "disabled")
+
+    def test_bad_status_value(self):
+        bad_body = {"status": "bad"}
+        self.assertRaises(webob.exc.HTTPBadRequest, self.controller.update,
+                self.req, "host_c1", body=bad_body)
+
+    def test_bad_update_key(self):
+        bad_body = {"crazy": "bad"}
+        self.assertRaises(webob.exc.HTTPBadRequest, self.controller.update,
+                self.req, "host_c1", body=bad_body)
+
+    def test_bad_host(self):
+        self.assertRaises(exception.HostNotFound, self.controller.update,
+                self.req, "bogus_host_name", body={"status": "disable"})
diff --git a/nova/tests/test_xenapi.py b/nova/tests/test_xenapi.py
index af7f7f338..4cb7447d3 100644
--- a/nova/tests/test_xenapi.py
+++ b/nova/tests/test_xenapi.py
@@ -381,6 +381,18 @@ class XenAPIVMTestCase(test.TestCase):
         self.assertEquals(self.vm['HVM_boot_params'], {})
         self.assertEquals(self.vm['HVM_boot_policy'], '')
 
+    def _list_vdis(self):
+        url = FLAGS.xenapi_connection_url
+        username = FLAGS.xenapi_connection_username
+        password = FLAGS.xenapi_connection_password
+        session = xenapi_conn.XenAPISession(url, username, password)
+        return session.call_xenapi('VDI.get_all')
+
+    def _check_vdis(self, start_list, end_list):
+        for vdi_ref in end_list:
+            if not vdi_ref in start_list:
+                self.fail('Found unexpected VDI:%s' % vdi_ref)
+
     def _test_spawn(self, image_ref, kernel_id, ramdisk_id,
                     instance_type_id="3", os_type="linux",
                     architecture="x86-64", instance_id=1,
@@ -422,6 +434,36 @@ class XenAPIVMTestCase(test.TestCase):
                           self._test_spawn,
                           1, 2, 3, "4")  # m1.xlarge
 
+    def test_spawn_fail_cleanup_1(self):
+        """Simulates an error while downloading an image.
+
+        Verifies that VDIs created are properly cleaned up.
+
+        """
+        vdi_recs_start = self._list_vdis()
+        FLAGS.xenapi_image_service = 'glance'
+        stubs.stubout_fetch_image_glance_disk(self.stubs)
+        self.assertRaises(xenapi_fake.Failure,
+                          self._test_spawn, 1, 2, 3)
+        # No additional VDI should be found.
+        vdi_recs_end = self._list_vdis()
+        self._check_vdis(vdi_recs_start, vdi_recs_end)
+
+    def test_spawn_fail_cleanup_2(self):
+        """Simulates an error while creating VM record.
+
+        It verifies that VDIs created are properly cleaned up.
+
+        """
+        vdi_recs_start = self._list_vdis()
+        FLAGS.xenapi_image_service = 'glance'
+        stubs.stubout_create_vm(self.stubs)
+        self.assertRaises(xenapi_fake.Failure,
+                          self._test_spawn, 1, 2, 3)
+        # No additional VDI should be found.
+        vdi_recs_end = self._list_vdis()
+        self._check_vdis(vdi_recs_start, vdi_recs_end)
+
     def test_spawn_raw_objectstore(self):
         FLAGS.xenapi_image_service = 'objectstore'
         self._test_spawn(1, None, None)
diff --git a/nova/tests/xenapi/stubs.py b/nova/tests/xenapi/stubs.py
index 151a3e909..66c79d465 100644
--- a/nova/tests/xenapi/stubs.py
+++ b/nova/tests/xenapi/stubs.py
@@ -98,6 +98,42 @@ def stubout_is_vdi_pv(stubs):
     stubs.Set(vm_utils, '_is_vdi_pv', f)
 
 
+def stubout_determine_is_pv_objectstore(stubs):
+    """Assumes VMs never have PV kernels"""
+
+    @classmethod
+    def f(cls, *args):
+        return False
+    stubs.Set(vm_utils.VMHelper, '_determine_is_pv_objectstore', f)
+
+
+def stubout_lookup_image(stubs):
+    """Simulates a failure in lookup image."""
+    def f(_1, _2, _3, _4):
+        raise Exception("Test Exception raised by fake lookup_image")
+    stubs.Set(vm_utils, 'lookup_image', f)
+
+
+def stubout_fetch_image_glance_disk(stubs):
+    """Simulates a failure in fetch image_glance_disk."""
+
+    @classmethod
+    def f(cls, *args):
+        raise fake.Failure("Test Exception raised by " +
+                           "fake fetch_image_glance_disk")
+    stubs.Set(vm_utils.VMHelper, '_fetch_image_glance_disk', f)
+
+
+def stubout_create_vm(stubs):
+    """Simulates a failure in create_vm."""
+
+    @classmethod
+    def f(cls, *args):
+        raise fake.Failure("Test Exception raised by " +
+                           "fake create_vm")
+    stubs.Set(vm_utils.VMHelper, 'create_vm', f)
+
+
 def stubout_loopingcall_start(stubs):
     def fake_start(self, interval, now=True):
         self.f(*self.args, **self.kw)
@@ -120,6 +156,9 @@ class FakeSessionForVMTests(fake.SessionBase):
         super(FakeSessionForVMTests, self).__init__(uri)
 
     def host_call_plugin(self, _1, _2, plugin, method, _5):
+        # If the call is for 'copy_kernel_vdi' return None.
+        if method == 'copy_kernel_vdi':
+            return
         sr_ref = fake.get_all('SR')[0]
         vdi_ref = fake.create_vdi('', False, sr_ref, False)
         vdi_rec = fake.get_record('VDI', vdi_ref)
diff --git a/nova/virt/driver.py b/nova/virt/driver.py
index 1c9797973..3c4a073bf 100644
--- a/nova/virt/driver.py
+++ b/nova/virt/driver.py
@@ -249,3 +249,7 @@ class ComputeDriver(object):
     def poll_rescued_instances(self, timeout):
         """Poll for rescued instances"""
         raise NotImplementedError()
+
+    def set_host_enabled(self, host, enabled):
+        """Sets the specified host's ability to accept new instances."""
+        raise NotImplementedError()
diff --git a/nova/virt/fake.py b/nova/virt/fake.py
index 5fe9d674f..ea0a59f21 100644
--- a/nova/virt/fake.py
+++ b/nova/virt/fake.py
@@ -514,3 +514,7 @@ class FakeConnection(driver.ComputeDriver):
     def get_host_stats(self, refresh=False):
         """Return fake Host Status of ram, disk, network."""
         return self.host_status
+
+    def set_host_enabled(self, host, enabled):
+        """Sets the specified host's ability to accept new instances."""
+        pass
diff --git a/nova/virt/hyperv.py b/nova/virt/hyperv.py
index f6783f3aa..5c1dc772d 100644
--- a/nova/virt/hyperv.py
+++ b/nova/virt/hyperv.py
@@ -499,3 +499,7 @@ class HyperVConnection(driver.ComputeDriver):
     def get_host_stats(self, refresh=False):
         """See xenapi_conn.py implementation."""
         pass
+
+    def set_host_enabled(self, host, enabled):
+        """Sets the specified host's ability to accept new instances."""
+        pass
diff --git a/nova/virt/libvirt/connection.py b/nova/virt/libvirt/connection.py
index 0c6eaab84..e912c2bec 100644
--- a/nova/virt/libvirt/connection.py
+++ b/nova/virt/libvirt/connection.py
@@ -1015,7 +1015,7 @@ class LibvirtConnection(driver.ComputeDriver):
                     'volumes': block_device_mapping}
 
         if FLAGS.vnc_enabled:
-            if FLAGS.libvirt_type != 'lxc':
+            if FLAGS.libvirt_type != 'lxc' or FLAGS.libvirt_type != 'uml':
                 xml_info['vncserver_host'] = FLAGS.vncserver_host
                 xml_info['vnc_keymap'] = FLAGS.vnc_keymap
         if not rescue:
@@ -1591,3 +1591,7 @@ class LibvirtConnection(driver.ComputeDriver):
     def get_host_stats(self, refresh=False):
         """See xenapi_conn.py implementation."""
         pass
+
+    def set_host_enabled(self, host, enabled):
+        """Sets the specified host's ability to accept new instances."""
+        pass
diff --git a/nova/virt/vmwareapi_conn.py b/nova/virt/vmwareapi_conn.py
index 3c6345ec8..d80e14931 100644
--- a/nova/virt/vmwareapi_conn.py
+++ b/nova/virt/vmwareapi_conn.py
@@ -190,6 +190,10 @@ class VMWareESXConnection(driver.ComputeDriver):
         """This method is supported only by libvirt."""

         return

 

+    def set_host_enabled(self, host, enabled):

+        """Sets the specified host's ability to accept new instances."""

+        pass

+

 

 class VMWareAPISession(object):

     """

diff --git a/nova/virt/xenapi/vm_utils.py b/nova/virt/xenapi/vm_utils.py
index f91958c57..71107aff4 100644
--- a/nova/virt/xenapi/vm_utils.py
+++ b/nova/virt/xenapi/vm_utils.py
@@ -23,6 +23,7 @@ import json
 import os
 import pickle
 import re
+import sys
 import tempfile
 import time
 import urllib
@@ -71,17 +72,51 @@ KERNEL_DIR = '/boot/guest'
 class ImageType:
     """
     Enumeration class for distinguishing different image types
-        0 - kernel/ramdisk image (goes on dom0's filesystem)
-        1 - disk image (local SR, partitioned by objectstore plugin)
-        2 - raw disk image (local SR, NOT partitioned by plugin)
-        3 - vhd disk image (local SR, NOT inspected by XS, PV assumed for
+        0 - kernel image (goes on dom0's filesystem)
+        1 - ramdisk image (goes on dom0's filesystem)
+        2 - disk image (local SR, partitioned by objectstore plugin)
+        3 - raw disk image (local SR, NOT partitioned by plugin)
+        4 - vhd disk image (local SR, NOT inspected by XS, PV assumed for
             linux, HVM assumed for Windows)
     """
 
-    KERNEL_RAMDISK = 0
-    DISK = 1
-    DISK_RAW = 2
-    DISK_VHD = 3
+    KERNEL = 0
+    RAMDISK = 1
+    DISK = 2
+    DISK_RAW = 3
+    DISK_VHD = 4
+
+    KERNEL_STR = "kernel"
+    RAMDISK_STR = "ramdisk"
+    DISK_STR = "os"
+    DISK_RAW_STR = "os_raw"
+    DISK_VHD_STR = "vhd"
+
+    @classmethod
+    def to_string(cls, image_type):
+        if image_type == ImageType.KERNEL:
+            return ImageType.KERNEL_STR
+        elif image_type == ImageType.RAMDISK:
+            return ImageType.RAMDISK_STR
+        elif image_type == ImageType.DISK:
+            return ImageType.DISK_STR
+        elif image_type == ImageType.DISK_RAW:
+            return ImageType.DISK_RAW_STR
+        elif image_type == ImageType.DISK_VHD:
+            return ImageType.VHD_STR
+
+    @classmethod
+    def from_string(cls, image_type_str):
+        if image_type_str == ImageType.KERNEL_STR:
+            return ImageType.KERNEL
+        elif image_type == ImageType.RAMDISK_STR:
+            return ImageType.RAMDISK
+        elif image_type == ImageType.DISK_STR:
+            return ImageType.DISK
+        elif image_type == ImageType.DISK_RAW_STR:
+            return ImageType.DISK_RAW
+        elif image_type == ImageType.DISK_VHD_STR:
+            return ImageType.VHD
 
 
 class VMHelper(HelperBase):
@@ -145,7 +180,6 @@ class VMHelper(HelperBase):
             'VCPUs_max': vcpus,
             'VCPUs_params': {},
             'xenstore_data': {}}
-
         # Complete VM configuration record according to the image type
         # non-raw/raw with PV kernel/raw in HVM mode
         if use_pv_kernel:
@@ -240,6 +274,15 @@ class VMHelper(HelperBase):
             raise StorageError(_('Unable to destroy VBD %s') % vbd_ref)
 
     @classmethod
+    def destroy_vdi(cls, session, vdi_ref):
+        try:
+            task = session.call_xenapi('Async.VDI.destroy', vdi_ref)
+            session.wait_for_task(task)
+        except cls.XenAPI.Failure, exc:
+            LOG.exception(exc)
+            raise StorageError(_('Unable to destroy VDI %s') % vdi_ref)
+
+    @classmethod
     def create_vif(cls, session, vm_ref, network_ref, mac_address,
                    dev, rxtx_cap=0):
         """Create a VIF record.  Returns a Deferred that gives the new
@@ -394,12 +437,12 @@ class VMHelper(HelperBase):
         """
         LOG.debug(_("Asking xapi to fetch vhd image %(image)s")
                     % locals())
-
         sr_ref = safe_find_sr(session)
 
-        # NOTE(sirp): The Glance plugin runs under Python 2.4 which does not
-        # have the `uuid` module. To work around this, we generate the uuids
-        # here (under Python 2.6+) and pass them as arguments
+        # NOTE(sirp): The Glance plugin runs under Python 2.4
+        # which does not have the `uuid` module. To work around this,
+        # we generate the uuids here (under Python 2.6+) and
+        # pass them as arguments
         uuid_stack = [str(uuid.uuid4()) for i in xrange(2)]
 
         glance_host, glance_port = \
@@ -449,18 +492,20 @@ class VMHelper(HelperBase):
         # FIXME(sirp): Since the Glance plugin seems to be required for the
         # VHD disk, it may be worth using the plugin for both VHD and RAW and
         # DISK restores
+        LOG.debug(_("Fetching image %(image)s") % locals())
+        LOG.debug(_("Image Type: %s"), ImageType.to_string(image_type))
         sr_ref = safe_find_sr(session)
 
         glance_client, image_id = nova.image.get_glance_client(image)
         meta, image_file = glance_client.get_image(image_id)
         virtual_size = int(meta['size'])
         vdi_size = virtual_size
-        LOG.debug(_("Size for image %(image)s:%(virtual_size)d") % locals())
-
+        LOG.debug(_("Size for image %(image)s:" +
+                    "%(virtual_size)d") % locals())
         if image_type == ImageType.DISK:
             # Make room for MBR.
             vdi_size += MBR_SIZE_BYTES
-        elif image_type == ImageType.KERNEL_RAMDISK and \
+        elif image_type in (ImageType.KERNEL, ImageType.RAMDISK) and \
              vdi_size > FLAGS.max_kernel_ramdisk_size:
             max_size = FLAGS.max_kernel_ramdisk_size
             raise exception.Error(
@@ -469,29 +514,45 @@ class VMHelper(HelperBase):
 
         name_label = get_name_label_for_image(image)
         vdi_ref = cls.create_vdi(session, sr_ref, name_label, vdi_size, False)
-
-        with_vdi_attached_here(session, vdi_ref, False,
-                               lambda dev:
-                               _stream_disk(dev, image_type,
-                                            virtual_size, image_file))
-        if image_type == ImageType.KERNEL_RAMDISK:
-            #we need to invoke a plugin for copying VDI's
-            #content into proper path
-            LOG.debug(_("Copying VDI %s to /boot/guest on dom0"), vdi_ref)
-            fn = "copy_kernel_vdi"
-            args = {}
-            args['vdi-ref'] = vdi_ref
-            #let the plugin copy the correct number of bytes
-            args['image-size'] = str(vdi_size)
-            task = session.async_call_plugin('glance', fn, args)
-            filename = session.wait_for_task(task, instance_id)
-            #remove the VDI as it is not needed anymore
-            session.get_xenapi().VDI.destroy(vdi_ref)
-            LOG.debug(_("Kernel/Ramdisk VDI %s destroyed"), vdi_ref)
-            return filename
-        else:
+        # From this point we have a VDI on Xen host;
+        # If anything goes wrong, we need to remember its uuid.
+        try:
+            filename = None
             vdi_uuid = session.get_xenapi().VDI.get_uuid(vdi_ref)
-            return [dict(vdi_type='os', vdi_uuid=vdi_uuid)]
+            with_vdi_attached_here(session, vdi_ref, False,
+                                   lambda dev:
+                                   _stream_disk(dev, image_type,
+                                                virtual_size, image_file))
+            if image_type in (ImageType.KERNEL, ImageType.RAMDISK):
+                # We need to invoke a plugin for copying the
+                # content of the VDI into the proper path.
+                LOG.debug(_("Copying VDI %s to /boot/guest on dom0"), vdi_ref)
+                fn = "copy_kernel_vdi"
+                args = {}
+                args['vdi-ref'] = vdi_ref
+                # Let the plugin copy the correct number of bytes.
+                args['image-size'] = str(vdi_size)
+                task = session.async_call_plugin('glance', fn, args)
+                filename = session.wait_for_task(task, instance_id)
+                # Remove the VDI as it is not needed anymore.
+                session.get_xenapi().VDI.destroy(vdi_ref)
+                LOG.debug(_("Kernel/Ramdisk VDI %s destroyed"), vdi_ref)
+                return [dict(vdi_type=ImageType.to_string(image_type),
+                             vdi_uuid=None,
+                             file=filename)]
+            else:
+                return [dict(vdi_type=ImageType.to_string(image_type),
+                             vdi_uuid=vdi_uuid,
+                             file=None)]
+        except (cls.XenAPI.Failure, IOError, OSError) as e:
+            # We look for XenAPI and OS failures.
+            LOG.exception(_("instance %s: Failed to fetch glance image"),
+                          instance_id, exc_info=sys.exc_info())
+            e.args = e.args + ([dict(vdi_type=ImageType.
+                                              to_string(image_type),
+                                    vdi_uuid=vdi_uuid,
+                                    file=filename)],)
+            raise e
 
     @classmethod
     def determine_disk_image_type(cls, instance):
@@ -506,7 +567,8 @@ class VMHelper(HelperBase):
            whether a kernel_id is specified.
         """
         def log_disk_format(image_type):
-            pretty_format = {ImageType.KERNEL_RAMDISK: 'KERNEL_RAMDISK',
+            pretty_format = {ImageType.KERNEL: 'KERNEL',
+                             ImageType.RAMDISK: 'RAMDISK',
                              ImageType.DISK: 'DISK',
                              ImageType.DISK_RAW: 'DISK_RAW',
                              ImageType.DISK_VHD: 'DISK_VHD'}
@@ -519,8 +581,8 @@ class VMHelper(HelperBase):
         def determine_from_glance():
             glance_disk_format2nova_type = {
                 'ami': ImageType.DISK,
-                'aki': ImageType.KERNEL_RAMDISK,
-                'ari': ImageType.KERNEL_RAMDISK,
+                'aki': ImageType.KERNEL,
+                'ari': ImageType.RAMDISK,
                 'raw': ImageType.DISK_RAW,
                 'vhd': ImageType.DISK_VHD}
             image_ref = instance.image_ref
@@ -553,7 +615,7 @@ class VMHelper(HelperBase):
                             image_type):
         """Fetch image from glance based on image type.
 
-        Returns: A single filename if image_type is KERNEL_RAMDISK
+        Returns: A single filename if image_type is KERNEL or RAMDISK
                  A list of dictionaries that describe VDIs, otherwise
         """
         if image_type == ImageType.DISK_VHD:
@@ -568,13 +630,13 @@ class VMHelper(HelperBase):
                                  secret, image_type):
         """Fetch an image from objectstore.
 
-        Returns: A single filename if image_type is KERNEL_RAMDISK
+        Returns: A single filename if image_type is KERNEL or RAMDISK
                  A list of dictionaries that describe VDIs, otherwise
         """
         url = "http://%s:%s/_images/%s/image" % (FLAGS.s3_host, FLAGS.s3_port,
                                                  image)
         LOG.debug(_("Asking xapi to fetch %(url)s as %(access)s") % locals())
-        if image_type == ImageType.KERNEL_RAMDISK:
+        if image_type in (ImageType.KERNEL, ImageType.RAMDISK):
             fn = 'get_kernel'
         else:
             fn = 'get_vdi'
@@ -584,15 +646,20 @@ class VMHelper(HelperBase):
         args['password'] = secret
         args['add_partition'] = 'false'
         args['raw'] = 'false'
-        if image_type != ImageType.KERNEL_RAMDISK:
+        if not image_type in (ImageType.KERNEL, ImageType.RAMDISK):
             args['add_partition'] = 'true'
             if image_type == ImageType.DISK_RAW:
                 args['raw'] = 'true'
         task = session.async_call_plugin('objectstore', fn, args)
-        uuid_or_fn = session.wait_for_task(task, instance_id)
-        if image_type != ImageType.KERNEL_RAMDISK:
-            return [dict(vdi_type='os', vdi_uuid=uuid_or_fn)]
-        return uuid_or_fn
+        vdi_uuid = None
+        filename = None
+        if image_type in (ImageType.KERNEL, ImageType.RAMDISK):
+            filename = session.wait_for_task(task, instance_id)
+        else:
+            vdi_uuid = session.wait_for_task(task, instance_id)
+        return [dict(vdi_type=ImageType.to_string(image_type),
+                     vdi_uuid=vdi_uuid,
+                     file=filename)]
 
     @classmethod
     def determine_is_pv(cls, session, instance_id, vdi_ref, disk_image_type,
diff --git a/nova/virt/xenapi/vmops.py b/nova/virt/xenapi/vmops.py
index b116c8467..56718f8e8 100644
--- a/nova/virt/xenapi/vmops.py
+++ b/nova/virt/xenapi/vmops.py
@@ -24,7 +24,9 @@ import json
 import M2Crypto
 import os
 import pickle
+import random
 import subprocess
+import sys
 import time
 import uuid
 
@@ -137,9 +139,18 @@ class VMOps(object):
         return vdis
 
     def spawn(self, instance, network_info):
-        vdis = self._create_disks(instance)
-        vm_ref = self._create_vm(instance, vdis, network_info)
-        self._spawn(instance, vm_ref)
+        vdis = None
+        try:
+            vdis = self._create_disks(instance)
+            vm_ref = self._create_vm(instance, vdis, network_info)
+            self._spawn(instance, vm_ref)
+        except (self.XenAPI.Failure, OSError, IOError) as spawn_error:
+            LOG.exception(_("instance %s: Failed to spawn"),
+                          instance.id, exc_info=sys.exc_info())
+            LOG.debug(_('Instance %s failed to spawn - performing clean-up'),
+                      instance.id)
+            self._handle_spawn_error(vdis, spawn_error)
+            raise spawn_error
 
     def spawn_rescue(self, instance):
         """Spawn a rescue instance."""
@@ -165,42 +176,64 @@ class VMOps(object):
         project = AuthManager().get_project(instance.project_id)
 
         disk_image_type = VMHelper.determine_disk_image_type(instance)
-
         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)
-
-        # Create the VM ref and attach the first disk
-        first_vdi_ref = self._session.call_xenapi('VDI.get_by_uuid',
-                vdis[0]['vdi_uuid'])
-
-        vm_mode = instance.vm_mode and instance.vm_mode.lower()
-        if vm_mode == 'pv':
-            use_pv_kernel = True
-        elif vm_mode in ('hv', 'hvm'):
-            use_pv_kernel = False
-            vm_mode = 'hvm'  # Normalize
-        else:
-            use_pv_kernel = VMHelper.determine_is_pv(self._session,
-                    instance.id, first_vdi_ref, disk_image_type,
-                    instance.os_type)
-            vm_mode = use_pv_kernel and 'pv' or 'hvm'
-
-        if instance.vm_mode != vm_mode:
-            # Update database with normalized (or determined) value
-            db.instance_update(context.get_admin_context(),
-                               instance['id'], {'vm_mode': vm_mode})
-
-        vm_ref = VMHelper.create_vm(self._session, instance,
-                kernel, ramdisk, use_pv_kernel)
+        try:
+            if instance.kernel_id:
+                kernel = VMHelper.fetch_image(self._session, instance.id,
+                        instance.kernel_id, user, project,
+                        ImageType.KERNEL)[0]
+            if instance.ramdisk_id:
+                ramdisk = VMHelper.fetch_image(self._session, instance.id,
+                        instance.ramdisk_id, user, project,
+                        ImageType.RAMDISK)[0]
+            # Create the VM ref and attach the first disk
+            first_vdi_ref = self._session.call_xenapi('VDI.get_by_uuid',
+                    vdis[0]['vdi_uuid'])
+
+            vm_mode = instance.vm_mode and instance.vm_mode.lower()
+            if vm_mode == 'pv':
+                use_pv_kernel = True
+            elif vm_mode in ('hv', 'hvm'):
+                use_pv_kernel = False
+                vm_mode = 'hvm'  # Normalize
+            else:
+                use_pv_kernel = VMHelper.determine_is_pv(self._session,
+                        instance.id, first_vdi_ref, disk_image_type,
+                        instance.os_type)
+                vm_mode = use_pv_kernel and 'pv' or 'hvm'
+
+            if instance.vm_mode != vm_mode:
+                # Update database with normalized (or determined) value
+                db.instance_update(context.get_admin_context(),
+                                   instance['id'], {'vm_mode': vm_mode})
+            vm_ref = VMHelper.create_vm(self._session, instance,
+                    kernel and kernel.get('file', None) or None,
+                    ramdisk and ramdisk.get('file', None) or None,
+                    use_pv_kernel)
+        except (self.XenAPI.Failure, OSError, IOError) as vm_create_error:
+            # Collect VDI/file resources to clean up;
+            # These resources will be removed by _handle_spawn_error.
+            LOG.exception(_("instance %s: Failed to spawn - " +
+                            "Unable to create VM"),
+                          instance.id, exc_info=sys.exc_info())
+            last_arg = None
+            resources = []
+
+            if vm_create_error.args:
+                last_arg = vm_create_error.args[-1]
+            if isinstance(last_arg, list):
+                resources = last_arg
+            else:
+                vm_create_error.args = vm_create_error.args + (resources,)
+
+            if kernel:
+                resources.append(kernel)
+            if ramdisk:
+                resources.append(ramdisk)
+
+            raise vm_create_error
+
         VMHelper.create_vbd(session=self._session, vm_ref=vm_ref,
                 vdi_ref=first_vdi_ref, userdevice=0, bootable=True)
 
@@ -321,6 +354,47 @@ class VMOps(object):
 
         return timer.start(interval=0.5, now=True)
 
+    def _handle_spawn_error(self, vdis, spawn_error):
+        # Extract resource list from spawn_error.
+        resources = []
+        if spawn_error.args:
+            last_arg = spawn_error.args[-1]
+            resources = last_arg
+        if vdis:
+            for vdi in vdis:
+                resources.append(dict(vdi_type=vdi['vdi_type'],
+                                      vdi_uuid=vdi['vdi_uuid'],
+                                      file=None))
+
+        LOG.debug(_("Resources to remove:%s"), resources)
+        kernel_file = None
+        ramdisk_file = None
+
+        for item in resources:
+            vdi_type = item['vdi_type']
+            vdi_to_remove = item['vdi_uuid']
+            if vdi_to_remove:
+                try:
+                    vdi_ref = self._session.call_xenapi('VDI.get_by_uuid',
+                            vdi_to_remove)
+                    LOG.debug(_('Removing VDI %(vdi_ref)s' +
+                                '(uuid:%(vdi_to_remove)s)'), locals())
+                    VMHelper.destroy_vdi(self._session, vdi_ref)
+                except self.XenAPI.Failure:
+                    # Vdi has already been deleted
+                    LOG.debug(_("Skipping VDI destroy for %s"), vdi_to_remove)
+            if item['file']:
+                # There is also a file to remove.
+                if vdi_type == ImageType.KERNEL_STR:
+                    kernel_file = item['file']
+                elif vdi_type == ImageType.RAMDISK_STR:
+                    ramdisk_file = item['file']
+
+        if kernel_file or ramdisk_file:
+            LOG.debug(_("Removing kernel/ramdisk files from dom0"))
+            self._destroy_kernel_ramdisk_plugin_call(kernel_file,
+                                                     ramdisk_file)
+
     def _get_vm_opaque_ref(self, instance_or_vm):
         """
         Refactored out the common code of many methods that receive either
@@ -698,6 +772,16 @@ class VMOps(object):
                 VMHelper.unplug_vbd(self._session, vbd_ref)
                 VMHelper.destroy_vbd(self._session, vbd_ref)
 
+    def _destroy_kernel_ramdisk_plugin_call(self, kernel, ramdisk):
+        args = {}
+        if kernel:
+            args['kernel-file'] = kernel
+        if ramdisk:
+            args['ramdisk-file'] = ramdisk
+        task = self._session.async_call_plugin(
+            'glance', 'remove_kernel_ramdisk', args)
+        self._session.wait_for_task(task)
+
     def _destroy_kernel_ramdisk(self, instance, vm_ref):
         """Three situations can occur:
 
@@ -727,13 +811,7 @@ class VMOps(object):
         (kernel, ramdisk) = VMHelper.lookup_kernel_ramdisk(self._session,
                                                            vm_ref)
 
-        LOG.debug(_("Removing kernel/ramdisk files"))
-
-        args = {'kernel-file': kernel, 'ramdisk-file': ramdisk}
-        task = self._session.async_call_plugin(
-            'glance', 'remove_kernel_ramdisk', args)
-        self._session.wait_for_task(task, instance.id)
-
+        self._destroy_kernel_ramdisk_plugin_call(kernel, ramdisk)
         LOG.debug(_("kernel/ramdisk files removed"))
 
     def _destroy_vm(self, instance, vm_ref):
@@ -932,6 +1010,31 @@ class VMOps(object):
         # TODO: implement this!
         return 'http://fakeajaxconsole/fake_url'
 
+    def set_host_enabled(self, host, enabled):
+        """Sets the specified host's ability to accept new instances."""
+        args = {"enabled": json.dumps(enabled)}
+        json_resp = self._call_xenhost("set_host_enabled", args)
+        resp = json.loads(json_resp)
+        return resp["status"]
+
+    def _call_xenhost(self, method, arg_dict):
+        """There will be several methods that will need this general
+        handling for interacting with the xenhost plugin, so this abstracts
+        out that behavior.
+        """
+        # Create a task ID as something that won't match any instance ID
+        task_id = random.randint(-80000, -70000)
+        try:
+            task = self._session.async_call_plugin("xenhost", method,
+                    args=arg_dict)
+                    #args={"params": arg_dict})
+            ret = self._session.wait_for_task(task, task_id)
+        except self.XenAPI.Failure as e:
+            ret = None
+            LOG.error(_("The call to %(method)s returned an error: %(e)s.")
+                    % locals())
+        return ret
+
     def inject_network_info(self, instance, network_info, vm_ref=None):
         """
         Generate the network info and make calls to place it into the
diff --git a/nova/virt/xenapi_conn.py b/nova/virt/xenapi_conn.py
index cd4dc1b60..ec8c44c1c 100644
--- a/nova/virt/xenapi_conn.py
+++ b/nova/virt/xenapi_conn.py
@@ -336,6 +336,10 @@ class XenAPIConnection(driver.ComputeDriver):
            True, run the update first."""
         return self.HostState.get_host_stats(refresh=refresh)
 
+    def set_host_enabled(self, host, enabled):
+        """Sets the specified host's ability to accept new instances."""
+        return self._vmops.set_host_enabled(host, enabled)
+
 
 class XenAPISession(object):
     """The session to invoke XenAPI SDK calls"""
diff --git a/plugins/xenserver/xenapi/etc/xapi.d/plugins/glance b/plugins/xenserver/xenapi/etc/xapi.d/plugins/glance
index 46031ebe8..fbe080b22 100644
--- a/plugins/xenserver/xenapi/etc/xapi.d/plugins/glance
+++ b/plugins/xenserver/xenapi/etc/xapi.d/plugins/glance
@@ -412,8 +412,8 @@ def copy_kernel_vdi(session, args):
 
 def remove_kernel_ramdisk(session, args):
     """Removes kernel and/or ramdisk from dom0's file system"""
-    kernel_file = exists(args, 'kernel-file')
-    ramdisk_file = exists(args, 'ramdisk-file')
+    kernel_file = optional(args, 'kernel-file')
+    ramdisk_file = optional(args, 'ramdisk-file')
     if kernel_file:
         os.remove(kernel_file)
     if ramdisk_file:
diff --git a/plugins/xenserver/xenapi/etc/xapi.d/plugins/xenhost b/plugins/xenserver/xenapi/etc/xapi.d/plugins/xenhost
index a8428e841..292bbce12 100644
--- a/plugins/xenserver/xenapi/etc/xapi.d/plugins/xenhost
+++ b/plugins/xenserver/xenapi/etc/xapi.d/plugins/xenhost
@@ -33,9 +33,10 @@ import tempfile
 import time
 
 import XenAPIPlugin
+import pluginlib_nova as pluginlib
 
-from pluginlib_nova import *
-configure_logging("xenhost")
+
+pluginlib.configure_logging("xenhost")
 
 host_data_pattern = re.compile(r"\s*(\S+) \([^\)]+\) *: ?(.*)")
 
@@ -65,14 +66,49 @@ def _run_command(cmd):
     return proc.stdout.read()
 
 
+def _get_host_uuid():
+    cmd = "xe host-list | grep uuid"
+    resp = _run_command(cmd)
+    return resp.split(":")[-1].strip()
+
+
+@jsonify
+def set_host_enabled(self, arg_dict):
+    """Sets this host's ability to accept new instances.
+    It will otherwise continue to operate normally.
+    """
+    enabled = arg_dict.get("enabled")
+    if enabled is None:
+        raise pluginlib.PluginError(
+                _("Missing 'enabled' argument to set_host_enabled"))
+    if enabled == "true":
+        result = _run_command("xe host-enable")
+    elif enabled == "false":
+        result = _run_command("xe host-disable")
+    else:
+        raise pluginlib.PluginError(_("Illegal enabled status: %s") % enabled)
+    # Should be empty string
+    if result:
+        raise pluginlib.PluginError(result)
+    # Return the current enabled status
+    host_uuid = _get_host_uuid()
+    cmd = "xe host-param-list uuid=%s | grep enabled" % host_uuid
+    resp = _run_command(cmd)
+    # Response should be in the format: "enabled ( RO): true"
+    host_enabled = resp.strip().split()[-1]
+    if host_enabled == "true":
+        status = "enabled"
+    else:
+        status = "disabled"
+    return {"status": status}
+
+
 @jsonify
 def host_data(self, arg_dict):
     """Runs the commands on the xenstore host to return the current status
     information.
     """
-    cmd = "xe host-list | grep uuid"
-    resp = _run_command(cmd)
-    host_uuid = resp.split(":")[-1].strip()
+    host_uuid = _get_host_uuid()
     cmd = "xe host-param-list uuid=%s" % host_uuid
     resp = _run_command(cmd)
     parsed_data = parse_response(resp)
@@ -180,4 +216,5 @@ def cleanup(dct):
 
 if __name__ == "__main__":
     XenAPIPlugin.dispatch(
-        {"host_data": host_data})
+            {"host_data": host_data,
+            "set_host_enabled": set_host_enabled})