This branch adds support to the xenapi driver for updating the guest agent on creation of a new instance. This ensures that the guest agent is running the latest code before nova starts configuring networking, setting root password or injecting files.

bin/nova-manage

@@ -1071,6 +1071,70 @@ class ImageCommands(object):
         self._convert_images(machine_images)
 
 
+class AgentBuildCommands(object):
+    """Class for managing agent builds."""
+
+    def create(self, os, architecture, version, url, md5hash,
+                hypervisor='xen'):
+        """Creates a new agent build.
+        arguments: os architecture version url md5hash [hypervisor='xen']"""
+        ctxt = context.get_admin_context()
+        agent_build = db.agent_build_create(ctxt,
+                                            {'hypervisor': hypervisor,
+                                             'os': os,
+                                             'architecture': architecture,
+                                             'version': version,
+                                             'url': url,
+                                             'md5hash': md5hash})
+
+    def delete(self, os, architecture, hypervisor='xen'):
+        """Deletes an existing agent build.
+        arguments: os architecture [hypervisor='xen']"""
+        ctxt = context.get_admin_context()
+        agent_build_ref = db.agent_build_get_by_triple(ctxt,
+                                  hypervisor, os, architecture)
+        db.agent_build_destroy(ctxt, agent_build_ref['id'])
+
+    def list(self, hypervisor=None):
+        """Lists all agent builds.
+        arguments: <none>"""
+        fmt = "%-10s  %-8s  %12s  %s"
+        ctxt = context.get_admin_context()
+        by_hypervisor = {}
+        for agent_build in db.agent_build_get_all(ctxt):
+            buildlist = by_hypervisor.get(agent_build.hypervisor)
+            if not buildlist:
+                buildlist = by_hypervisor[agent_build.hypervisor] = []
+
+            buildlist.append(agent_build)
+
+        for key, buildlist in by_hypervisor.iteritems():
+            if hypervisor and key != hypervisor:
+                continue
+
+            print "Hypervisor: %s" % key
+            print fmt % ('-' * 10, '-' * 8, '-' * 12, '-' * 32)
+            for agent_build in buildlist:
+                print fmt % (agent_build.os, agent_build.architecture,
+                             agent_build.version, agent_build.md5hash)
+                print '    %s' % agent_build.url
+
+            print
+
+    def modify(self, os, architecture, version, url, md5hash,
+               hypervisor='xen'):
+        """Update an existing agent build.
+        arguments: os architecture version url md5hash [hypervisor='xen']
+        """
+        ctxt = context.get_admin_context()
+        agent_build_ref = db.agent_build_get_by_triple(ctxt,
+                                  hypervisor, os, architecture)
+        db.agent_build_update(ctxt, agent_build_ref['id'],
+                              {'version': version,
+                               'url': url,
+                               'md5hash': md5hash})
+
+
 class ConfigCommands(object):
     """Class for exposing the flags defined by flag_file(s)."""
 
@@ -1083,6 +1147,7 @@ class ConfigCommands(object):
 
 CATEGORIES = [
     ('account', AccountCommands),
+    ('agent', AgentBuildCommands),
     ('config', ConfigCommands),
     ('db', DbCommands),
     ('fixed', FixedIpCommands),

nova/compute/api.py

@@ -178,6 +178,9 @@ class API(base.Base):
         os_type = None
         if 'properties' in image and 'os_type' in image['properties']:
             os_type = image['properties']['os_type']
+        architecture = None
+        if 'properties' in image and 'arch' in image['properties']:
+            architecture = image['properties']['arch']
         vm_mode = None
         if 'properties' in image and 'vm_mode' in image['properties']:
             vm_mode = image['properties']['vm_mode']
@@ -243,6 +246,7 @@ class API(base.Base):
             'metadata': metadata,
             'availability_zone': availability_zone,
             'os_type': os_type,
+            'architecture': architecture,
             'vm_mode': vm_mode}
 
         return (num_instances, base_options, security_groups)

nova/compute/manager.py

@@ -560,6 +560,24 @@ class ComputeManager(manager.SchedulerDependentManager):
         LOG.audit(msg)
         self.driver.inject_file(instance_ref, path, file_contents)
 
+    @exception.wrap_exception
+    @checks_instance_lock
+    def agent_update(self, context, instance_id, url, md5hash):
+        """Update agent running on an instance on this host."""
+        context = context.elevated()
+        instance_ref = self.db.instance_get(context, instance_id)
+        instance_id = instance_ref['id']
+        instance_state = instance_ref['state']
+        expected_state = power_state.RUNNING
+        if instance_state != expected_state:
+            LOG.warn(_('trying to update agent on a non-running '
+                    'instance: %(instance_id)s (state: %(instance_state)s '
+                    'expected: %(expected_state)s)') % locals())
+        nm = instance_ref['name']
+        msg = _('instance %(nm)s: updating agent to %(url)s') % locals()
+        LOG.audit(msg)
+        self.driver.agent_update(instance_ref, url, md5hash)
+
     @exception.wrap_exception
     @checks_instance_lock
     def rescue_instance(self, context, instance_id):

nova/db/api.py

@@ -1287,3 +1287,32 @@ def instance_metadata_delete(context, instance_id, key):
 def instance_metadata_update_or_create(context, instance_id, metadata):
     """Create or update instance metadata."""
     IMPL.instance_metadata_update_or_create(context, instance_id, metadata)
+
+
+####################
+
+
+def agent_build_create(context, values):
+    """Create a new agent build entry."""
+    return IMPL.agent_build_create(context, values)
+
+
+def agent_build_get_by_triple(context, hypervisor, os, architecture):
+    """Get agent build by hypervisor/OS/architecture triple."""
+    return IMPL.agent_build_get_by_triple(context, hypervisor, os,
+            architecture)
+
+
+def agent_build_get_all(context):
+    """Get all agent builds."""
+    return IMPL.agent_build_get_all(context)
+
+
+def agent_build_destroy(context, agent_update_id):
+    """Destroy agent build entry."""
+    IMPL.agent_build_destroy(context, agent_update_id)
+
+
+def agent_build_update(context, agent_build_id, values):
+    """Update agent build entry."""
+    IMPL.agent_build_update(context, agent_build_id, values)

nova/db/sqlalchemy/api.py

@@ -2792,3 +2792,54 @@ def instance_metadata_update_or_create(context, instance_id, metadata):
         meta_ref.save(session=session)
 
     return metadata
+
+
+@require_admin_context
+def agent_build_create(context, values):
+    agent_build_ref = models.AgentBuild()
+    agent_build_ref.update(values)
+    agent_build_ref.save()
+    return agent_build_ref
+
+
+@require_admin_context
+def agent_build_get_by_triple(context, hypervisor, os, architecture,
+                              session=None):
+    if not session:
+        session = get_session()
+    return session.query(models.AgentBuild).\
+                   filter_by(hypervisor=hypervisor).\
+                   filter_by(os=os).\
+                   filter_by(architecture=architecture).\
+                   filter_by(deleted=False).\
+                   first()
+
+
+@require_admin_context
+def agent_build_get_all(context):
+    session = get_session()
+    return session.query(models.AgentBuild).\
+                   filter_by(deleted=False).\
+                   all()
+
+
+@require_admin_context
+def agent_build_destroy(context, agent_build_id):
+    session = get_session()
+    with session.begin():
+        session.query(models.AgentBuild).\
+                filter_by(id=agent_build_id).\
+                update({'deleted': 1,
+                        'deleted_at': datetime.datetime.utcnow(),
+                        'updated_at': literal_column('updated_at')})
+
+
+@require_admin_context
+def agent_build_update(context, agent_build_id, values):
+    session = get_session()
+    with session.begin():
+        agent_build_ref = session.query(models.AgentBuild).\
+                   filter_by(id=agent_build_id). \
+                   first()
+        agent_build_ref.update(values)
+        agent_build_ref.save(session=session)

nova/db/sqlalchemy/migrate_repo/versions/026_add_agent_table.py

@@ -0,0 +1,73 @@
+# 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.
+
+from sqlalchemy import Boolean, Column, DateTime, Integer
+from sqlalchemy import MetaData, String, Table
+from nova import log as logging
+
+meta = MetaData()
+
+#
+# New Tables
+#
+builds = Table('agent_builds', 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('hypervisor',
+               String(length=255, convert_unicode=False, assert_unicode=None,
+                      unicode_error=None, _warn_on_bytestring=False)),
+        Column('os',
+               String(length=255, convert_unicode=False, assert_unicode=None,
+                      unicode_error=None, _warn_on_bytestring=False)),
+        Column('architecture',
+               String(length=255, convert_unicode=False, assert_unicode=None,
+                      unicode_error=None, _warn_on_bytestring=False)),
+        Column('version',
+               String(length=255, convert_unicode=False, assert_unicode=None,
+                      unicode_error=None, _warn_on_bytestring=False)),
+        Column('url',
+               String(length=255, convert_unicode=False, assert_unicode=None,
+                      unicode_error=None, _warn_on_bytestring=False)),
+        Column('md5hash',
+               String(length=255, convert_unicode=False, assert_unicode=None,
+                      unicode_error=None, _warn_on_bytestring=False)),
+        )
+
+
+#
+# New Column
+#
+
+architecture = Column('architecture', String(length=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 (builds, ):
+        try:
+            table.create()
+        except Exception:
+            logging.info(repr(table))
+
+    instances = Table('instances', meta, autoload=True,
+                      autoload_with=migrate_engine)
+
+    # Add columns to existing tables
+    instances.create_column(architecture)

nova/db/sqlalchemy/models.py

@@ -232,6 +232,7 @@ class Instance(BASE, NovaBase):
     locked = Column(Boolean)
 
     os_type = Column(String(255))
+    architecture = Column(String(255))
     vm_mode = Column(String(255))
     uuid = Column(String(36))
 
@@ -713,6 +714,18 @@ class Zone(BASE, NovaBase):
     password = Column(String(255))
 
 
+class AgentBuild(BASE, NovaBase):
+    """Represents an agent build."""
+    __tablename__ = 'agent_builds'
+    id = Column(Integer, primary_key=True)
+    hypervisor = Column(String(255))
+    os = Column(String(255))
+    architecture = Column(String(255))
+    version = Column(String(255))
+    url = Column(String(255))
+    md5hash = Column(String(255))
+
+
 def register_models():
     """Register Models and create metadata.
 
@@ -726,7 +739,7 @@ def register_models():
               Network, SecurityGroup, SecurityGroupIngressRule,
               SecurityGroupInstanceAssociation, AuthToken, User,
               Project, Certificate, ConsolePool, Console, Zone,
-              InstanceMetadata, Migration)
+              AgentBuild, InstanceMetadata, Migration)
     engine = create_engine(FLAGS.sql_connection, echo=False)
     for model in models:
         model.metadata.create_all(engine)

nova/tests/test_compute.py

@@ -281,6 +281,14 @@ class ComputeTestCase(test.TestCase):
                 "File Contents")
         self.compute.terminate_instance(self.context, instance_id)
 
+    def test_agent_update(self):
+        """Ensure instance can have its agent updated"""
+        instance_id = self._create_instance()
+        self.compute.run_instance(self.context, instance_id)
+        self.compute.agent_update(self.context, instance_id,
+                'http://127.0.0.1/agent', '00112233445566778899aabbccddeeff')
+        self.compute.terminate_instance(self.context, instance_id)
+
     def test_snapshot(self):
         """Ensure instance can be snapshotted"""
         instance_id = self._create_instance()

nova/tests/test_xenapi.py

@@ -37,9 +37,8 @@ from nova import exception
 from nova.virt import xenapi_conn
 from nova.virt.xenapi import fake as xenapi_fake
 from nova.virt.xenapi import volume_utils
+from nova.virt.xenapi import vmops
 from nova.virt.xenapi import vm_utils
-from nova.virt.xenapi.vmops import SimpleDH
-from nova.virt.xenapi.vmops import VMOps
 from nova.tests.db import fakes as db_fakes
 from nova.tests.xenapi import stubs
 from nova.tests.glance import stubs as glance_stubs
@@ -85,7 +84,8 @@ class XenAPIVolumeTestCase(test.TestCase):
                   'ramdisk_id': 3,
                   'instance_type_id': '3',  # m1.large
                   'mac_address': 'aa:bb:cc:dd:ee:ff',
-                  'os_type': 'linux'}
+                  'os_type': 'linux',
+                  'architecture': 'x86-64'}
 
     def _create_volume(self, size='0'):
         """Create a volume object."""
@@ -192,7 +192,7 @@ class XenAPIVMTestCase(test.TestCase):
         stubs.stubout_get_this_vm_uuid(self.stubs)
         stubs.stubout_stream_disk(self.stubs)
         stubs.stubout_is_vdi_pv(self.stubs)
-        self.stubs.Set(VMOps, 'reset_network', reset_network)
+        self.stubs.Set(vmops.VMOps, 'reset_network', reset_network)
         stubs.stub_out_vm_methods(self.stubs)
         glance_stubs.stubout_glance_client(self.stubs)
         fake_utils.stub_out_utils_execute(self.stubs)
@@ -212,7 +212,8 @@ class XenAPIVMTestCase(test.TestCase):
                 'ramdisk_id': 3,
                 'instance_type_id': '3',  # m1.large
                 'mac_address': 'aa:bb:cc:dd:ee:ff',
-                'os_type': 'linux'}
+                'os_type': 'linux',
+                'architecture': 'x86-64'}
             instance = db.instance_create(self.context, values)
             self.conn.spawn(instance)
 
@@ -370,7 +371,8 @@ class XenAPIVMTestCase(test.TestCase):
 
     def _test_spawn(self, image_ref, kernel_id, ramdisk_id,
                     instance_type_id="3", os_type="linux",
-                    instance_id=1, check_injection=False):
+                    architecture="x86-64", instance_id=1,
+                    check_injection=False):
         stubs.stubout_loopingcall_start(self.stubs)
         values = {'id': instance_id,
                   'project_id': self.project.id,
@@ -380,11 +382,14 @@ class XenAPIVMTestCase(test.TestCase):
                   'ramdisk_id': ramdisk_id,
                   'instance_type_id': instance_type_id,
                   'mac_address': 'aa:bb:cc:dd:ee:ff',
-                  'os_type': os_type}
+                  'os_type': os_type,
+                  'architecture': architecture}
         instance = db.instance_create(self.context, values)
         self.conn.spawn(instance)
         self.create_vm_record(self.conn, os_type, instance_id)
         self.check_vm_record(self.conn, check_injection)
+        self.assertTrue(instance.os_type)
+        self.assertTrue(instance.architecture)
 
     def test_spawn_not_enough_memory(self):
         FLAGS.xenapi_image_service = 'glance'
@@ -409,7 +414,7 @@ class XenAPIVMTestCase(test.TestCase):
     def test_spawn_vhd_glance_linux(self):
         FLAGS.xenapi_image_service = 'glance'
         self._test_spawn(glance_stubs.FakeGlance.IMAGE_VHD, None, None,
-                         os_type="linux")
+                         os_type="linux", architecture="x86-64")
         self.check_vm_params_for_linux()
 
     def test_spawn_vhd_glance_swapdisk(self):
@@ -438,7 +443,7 @@ class XenAPIVMTestCase(test.TestCase):
     def test_spawn_vhd_glance_windows(self):
         FLAGS.xenapi_image_service = 'glance'
         self._test_spawn(glance_stubs.FakeGlance.IMAGE_VHD, None, None,
-                         os_type="windows")
+                         os_type="windows", architecture="i386")
         self.check_vm_params_for_windows()
 
     def test_spawn_glance(self):
@@ -589,7 +594,8 @@ class XenAPIVMTestCase(test.TestCase):
             'ramdisk_id': 3,
             'instance_type_id': '3',  # m1.large
             'mac_address': 'aa:bb:cc:dd:ee:ff',
-            'os_type': 'linux'}
+            'os_type': 'linux',
+            'architecture': 'x86-64'}
         instance = db.instance_create(self.context, values)
         self.conn.spawn(instance)
         return instance
@@ -599,8 +605,8 @@ class XenAPIDiffieHellmanTestCase(test.TestCase):
     """Unit tests for Diffie-Hellman code."""
     def setUp(self):
         super(XenAPIDiffieHellmanTestCase, self).setUp()
-        self.alice = SimpleDH()
+        self.alice = vmops.SimpleDH()
-        self.bob = SimpleDH()
+        self.bob = vmops.SimpleDH()
 
     def test_shared(self):
         alice_pub = self.alice.get_public()
@@ -664,7 +670,8 @@ class XenAPIMigrateInstance(test.TestCase):
                   'local_gb': 5,
                   'instance_type_id': '3',  # m1.large
                   'mac_address': 'aa:bb:cc:dd:ee:ff',
-                  'os_type': 'linux'}
+                  'os_type': 'linux',
+                  'architecture': 'x86-64'}
 
         fake_utils.stub_out_utils_execute(self.stubs)
         stubs.stub_out_migration_methods(self.stubs)
@@ -703,6 +710,7 @@ class XenAPIDetermineDiskImageTestCase(test.TestCase):
         self.fake_instance = FakeInstance()
         self.fake_instance.id = 42
         self.fake_instance.os_type = 'linux'
+        self.fake_instance.architecture = 'x86-64'
 
     def assert_disk_type(self, disk_type):
         dt = vm_utils.VMHelper.determine_disk_image_type(
@@ -747,6 +755,28 @@ class XenAPIDetermineDiskImageTestCase(test.TestCase):
         self.assert_disk_type(vm_utils.ImageType.DISK_VHD)
 
 
+class CompareVersionTestCase(test.TestCase):
+    def test_less_than(self):
+        """Test that cmp_version compares a as less than b"""
+        self.assertTrue(vmops.cmp_version('1.2.3.4', '1.2.3.5') < 0)
+
+    def test_greater_than(self):
+        """Test that cmp_version compares a as greater than b"""
+        self.assertTrue(vmops.cmp_version('1.2.3.5', '1.2.3.4') > 0)
+
+    def test_equal(self):
+        """Test that cmp_version compares a as equal to b"""
+        self.assertTrue(vmops.cmp_version('1.2.3.4', '1.2.3.4') == 0)
+
+    def test_non_lexical(self):
+        """Test that cmp_version compares non-lexically"""
+        self.assertTrue(vmops.cmp_version('1.2.3.10', '1.2.3.4') > 0)
+
+    def test_length(self):
+        """Test that cmp_version compares by length as last resort"""
+        self.assertTrue(vmops.cmp_version('1.2.3', '1.2.3.4') < 0)
+
+
 class FakeXenApi(object):
     """Fake XenApi for testing HostState."""
 

nova/virt/driver.py

@@ -234,6 +234,10 @@ class ComputeDriver(object):
         """
         raise NotImplementedError()
 
+    def agent_update(self, instance, url, md5hash):
+        """Update agent on the VM instance."""
+        raise NotImplementedError()
+
     def inject_network_info(self, instance):
         """inject network info for specified instance"""
         raise NotImplementedError()

nova/virt/fake.py

@@ -225,6 +225,21 @@ class FakeConnection(driver.ComputeDriver):
         """
         pass
 
+    def agent_update(self, instance, url, md5hash):
+        """
+        Update agent on the specified instance.
+
+        The first parameter is an instance of nova.compute.service.Instance,
+        and so the instance is being specified as instance.name. The second
+        parameter is the URL of the agent to be fetched and updated on the
+        instance; the third is the md5 hash of the file for verification
+        purposes.
+
+        The work will be done asynchronously.  This function returns a
+        task that allows the caller to detect when it is complete.
+        """
+        pass
+
     def rescue(self, instance):
         """
         Rescue the specified instance.

nova/virt/xenapi/vmops.py

@@ -47,6 +47,21 @@ LOG = logging.getLogger("nova.virt.xenapi.vmops")
 FLAGS = flags.FLAGS
 
 
+def cmp_version(a, b):
+    """Compare two version strings (eg 0.0.1.10 > 0.0.1.9)"""
+    a = a.split('.')
+    b = b.split('.')
+
+    # Compare each individual portion of both version strings
+    for va, vb in zip(a, b):
+        ret = int(va) - int(vb)
+        if ret:
+            return ret
+
+    # Fallback to comparing length last
+    return len(a) - len(b)
+
+
 class VMOps(object):
     """
     Management class for VM-related tasks
@@ -218,6 +233,34 @@ class VMOps(object):
         LOG.info(_('Spawning VM %(instance_name)s created %(vm_ref)s.')
                  % locals())
 
+        ctx = context.get_admin_context()
+        agent_build = db.agent_build_get_by_triple(ctx, 'xen',
+                              instance.os_type, instance.architecture)
+        if agent_build:
+            LOG.info(_('Latest agent build for %(hypervisor)s/%(os)s' + \
+                       '/%(architecture)s is %(version)s') % agent_build)
+        else:
+            LOG.info(_('No agent build found for %(hypervisor)s/%(os)s' + \
+                       '/%(architecture)s') % {
+                        'hypervisor': 'xen',
+                        'os': instance.os_type,
+                        'architecture': instance.architecture})
+
+        def _check_agent_version():
+            version = self.get_agent_version(instance)
+            if not version:
+                LOG.info(_('No agent version returned by instance'))
+                return
+
+            LOG.info(_('Instance agent version: %s') % version)
+            if not agent_build:
+                return
+
+            if cmp_version(version, agent_build['version']) < 0:
+                LOG.info(_('Updating Agent to %s') % agent_build['version'])
+                self.agent_update(instance, agent_build['url'],
+                              agent_build['md5hash'])
+
         def _inject_files():
             injected_files = instance.injected_files
             if injected_files:
@@ -252,6 +295,7 @@ class VMOps(object):
                 if state == power_state.RUNNING:
                     LOG.debug(_('Instance %s: booted'), instance_name)
                     timer.stop()
+                    _check_agent_version()
                     _inject_files()
                     _set_admin_password()
                     return True
@@ -458,6 +502,34 @@ class VMOps(object):
         task = self._session.call_xenapi('Async.VM.clean_reboot', vm_ref)
         self._session.wait_for_task(task, instance.id)
 
+    def get_agent_version(self, instance):
+        """Get the version of the agent running on the VM instance."""
+
+        # Send the encrypted password
+        transaction_id = str(uuid.uuid4())
+        args = {'id': transaction_id}
+        resp = self._make_agent_call('version', instance, '', args)
+        if resp is None:
+            # No response from the agent
+            return
+        resp_dict = json.loads(resp)
+        return resp_dict['message']
+
+    def agent_update(self, instance, url, md5sum):
+        """Update agent on the VM instance."""
+
+        # Send the encrypted password
+        transaction_id = str(uuid.uuid4())
+        args = {'id': transaction_id, 'url': url, 'md5sum': md5sum}
+        resp = self._make_agent_call('agentupdate', instance, '', args)
+        if resp is None:
+            # No response from the agent
+            return
+        resp_dict = json.loads(resp)
+        if resp_dict['returncode'] != '0':
+            raise RuntimeError(resp_dict['message'])
+        return resp_dict['message']
+
     def set_admin_password(self, instance, new_pass):
         """Set the root/admin password on the VM instance.
 

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

@@ -53,6 +53,19 @@ class TimeoutError(StandardError):
     pass
 
 
+def version(self, arg_dict):
+    """Get version of agent."""
+    arg_dict["value"] = json.dumps({"name": "version", "value": ""})
+    request_id = arg_dict["id"]
+    arg_dict["path"] = "data/host/%s" % request_id
+    xenstore.write_record(self, arg_dict)
+    try:
+        resp = _wait_for_agent(self, request_id, arg_dict)
+    except TimeoutError, e:
+        raise PluginError(e)
+    return resp
+
+
 def key_init(self, arg_dict):
     """Handles the Diffie-Hellman key exchange with the agent to
     establish the shared secret key used to encrypt/decrypt sensitive
@@ -144,6 +157,23 @@ def inject_file(self, arg_dict):
     return resp
 
 
+def agent_update(self, arg_dict):
+    """Expects an URL and md5sum of the contents, then directs the agent to
+    update itself."""
+    request_id = arg_dict["id"]
+    url = arg_dict["url"]
+    md5sum = arg_dict["md5sum"]
+    arg_dict["value"] = json.dumps({"name": "agentupdate",
+                "value": {"url": url, "md5sum": md5sum}})
+    arg_dict["path"] = "data/host/%s" % request_id
+    xenstore.write_record(self, arg_dict)
+    try:
+        resp = _wait_for_agent(self, request_id, arg_dict)
+    except TimeoutError, e:
+        raise PluginError(e)
+    return resp
+
+
 def _agent_has_method(self, method):
     """Check that the agent has a particular method by checking its
     features.  Cache the features so we don't have to query the agent
@@ -201,7 +231,9 @@ def _wait_for_agent(self, request_id, arg_dict):
 
 if __name__ == "__main__":
     XenAPIPlugin.dispatch(
-        {"key_init": key_init,
+        {"version": version,
+        "key_init": key_init,
         "password": password,
         "resetnetwork": resetnetwork,
-        "inject_file": inject_file})
+        "inject_file": inject_file,
+        "agentupdate": agent_update})