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diff --git a/nova/virt/xenapi_conn.py b/nova/virt/xenapi_conn.py
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+# vim: tabstop=4 shiftwidth=4 softtabstop=4
+
+# Copyright (c) 2010 Citrix Systems, Inc.
+#
+#    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.
+
+"""
+A connection to XenServer or Xen Cloud Platform.
+
+The concurrency model for this class is as follows:
+
+All XenAPI calls are on a thread (using t.i.t.deferToThread, via the decorator
+deferredToThread).  They are remote calls, and so may hang for the usual
+reasons.  They should not be allowed to block the reactor thread.
+
+All long-running XenAPI calls (VM.start, VM.reboot, etc) are called async
+(using XenAPI.VM.async_start etc).  These return a task, which can then be
+polled for completion.  Polling is handled using reactor.callLater.
+
+This combination of techniques means that we don't block the reactor thread at
+all, and at the same time we don't hold lots of threads waiting for
+long-running operations.
+
+FIXME: get_info currently doesn't conform to these rules, and will block the
+reactor thread if the VM.get_by_name_label or VM.get_record calls block.
+
+**Related Flags**
+
+:xenapi_connection_url:  URL for connection to XenServer/Xen Cloud Platform.
+:xenapi_connection_username:  Username for connection to XenServer/Xen Cloud
+                              Platform (default: root).
+:xenapi_connection_password:  Password for connection to XenServer/Xen Cloud
+                              Platform.
+:xenapi_task_poll_interval:  The interval (seconds) used for polling of
+                             remote tasks (Async.VM.start, etc)
+                             (default: 0.5).
+
+"""
+
+import logging
+import xmlrpclib
+
+from twisted.internet import defer
+from twisted.internet import reactor
+
+from nova import utils
+from nova import flags
+from nova.virt.xenapi.vmops import VMOps
+from nova.virt.xenapi.volumeops import VolumeOps
+
+FLAGS = flags.FLAGS
+flags.DEFINE_string('xenapi_connection_url',
+                    None,
+                    'URL for connection to XenServer/Xen Cloud Platform.'
+                    ' Required if connection_type=xenapi.')
+flags.DEFINE_string('xenapi_connection_username',
+                    'root',
+                    'Username for connection to XenServer/Xen Cloud Platform.'
+                    ' Used only if connection_type=xenapi.')
+flags.DEFINE_string('xenapi_connection_password',
+                    None,
+                    'Password for connection to XenServer/Xen Cloud Platform.'
+                    ' Used only if connection_type=xenapi.')
+flags.DEFINE_float('xenapi_task_poll_interval',
+                   0.5,
+                   'The interval used for polling of remote tasks '
+                   '(Async.VM.start, etc).  Used only if '
+                   'connection_type=xenapi.')
+
+XenAPI = None
+
+
+def get_connection(_):
+    """Note that XenAPI doesn't have a read-only connection mode, so
+    the read_only parameter is ignored."""
+    # This is loaded late so that there's no need to install this
+    # library when not using XenAPI.
+    global XenAPI
+    if XenAPI is None:
+        XenAPI = __import__('XenAPI')
+    url = FLAGS.xenapi_connection_url
+    username = FLAGS.xenapi_connection_username
+    password = FLAGS.xenapi_connection_password
+    if not url or password is None:
+        raise Exception('Must specify xenapi_connection_url, '
+                        'xenapi_connection_username (optionally), and '
+                        'xenapi_connection_password to use '
+                        'connection_type=xenapi')
+    return XenAPIConnection(url, username, password)
+
+
+class XenAPIConnection(object):
+    """ A connection to XenServer or Xen Cloud Platform """
+    def __init__(self, url, user, pw):
+        session = XenAPISession(url, user, pw)
+        self._vmops = VMOps(session)
+        self._volumeops = VolumeOps(session)
+
+    def list_instances(self):
+        """ List VM instances """
+        return self._vmops.list_instances()
+
+    def spawn(self, instance):
+        """ Create VM instance """
+        self._vmops.spawn(instance)
+
+    def reboot(self, instance):
+        """ Reboot VM instance """
+        self._vmops.reboot(instance)
+
+    def destroy(self, instance):
+        """ Destroy VM instance """
+        self._vmops.destroy(instance)
+
+    def get_info(self, instance_id):
+        """ Return data about VM instance """
+        return self._vmops.get_info(instance_id)
+
+    def get_diagnostics(self, instance_id):
+        """Return data about VM diagnostics"""
+        return self._vmops.get_diagnostics(instance_id)
+
+    def get_console_output(self, instance):
+        """ Return snapshot of console """
+        return self._vmops.get_console_output(instance)
+
+    def attach_volume(self, instance_name, device_path, mountpoint):
+        """ Attach volume storage to VM instance """
+        return self._volumeops.attach_volume(instance_name,
+                                               device_path,
+                                               mountpoint)
+
+    def detach_volume(self, instance_name, mountpoint):
+        """ Detach volume storage to VM instance """
+        return self._volumeops.detach_volume(instance_name, mountpoint)
+
+
+class XenAPISession(object):
+    """ The session to invoke XenAPI SDK calls """
+    def __init__(self, url, user, pw):
+        self._session = XenAPI.Session(url)
+        self._session.login_with_password(user, pw)
+
+    def get_xenapi(self):
+        """ Return the xenapi object """
+        return self._session.xenapi
+
+    def get_xenapi_host(self):
+        """ Return the xenapi host """
+        return self._session.xenapi.session.get_this_host(self._session.handle)
+
+    @utils.deferredToThread
+    def call_xenapi(self, method, *args):
+        """Call the specified XenAPI method on a background thread.  Returns
+        a Deferred for the result."""
+        f = self._session.xenapi
+        for m in method.split('.'):
+            f = f.__getattr__(m)
+        return f(*args)
+
+    @utils.deferredToThread
+    def async_call_plugin(self, plugin, fn, args):
+        """Call Async.host.call_plugin on a background thread.  Returns a
+        Deferred with the task reference."""
+        return _unwrap_plugin_exceptions(
+            self._session.xenapi.Async.host.call_plugin,
+            self.get_xenapi_host(), plugin, fn, args)
+
+    def wait_for_task(self, task):
+        """Return a Deferred that will give the result of the given task.
+        The task is polled until it completes."""
+        d = defer.Deferred()
+        reactor.callLater(0, self._poll_task, task, d)
+        return d
+
+    @utils.deferredToThread
+    def _poll_task(self, task, deferred):
+        """Poll the given XenAPI task, and fire the given Deferred if we
+        get a result."""
+        try:
+            #logging.debug('Polling task %s...', task)
+            status = self._session.xenapi.task.get_status(task)
+            if status == 'pending':
+                reactor.callLater(FLAGS.xenapi_task_poll_interval,
+                                  self._poll_task, task, deferred)
+            elif status == 'success':
+                result = self._session.xenapi.task.get_result(task)
+                logging.info('Task %s status: success.  %s', task, result)
+                deferred.callback(_parse_xmlrpc_value(result))
+            else:
+                error_info = self._session.xenapi.task.get_error_info(task)
+                logging.warn('Task %s status: %s.  %s', task, status,
+                             error_info)
+                deferred.errback(XenAPI.Failure(error_info))
+            #logging.debug('Polling task %s done.', task)
+        except XenAPI.Failure, exc:
+            logging.warn(exc)
+            deferred.errback(exc)
+
+
+def _unwrap_plugin_exceptions(func, *args, **kwargs):
+    """ Parse exception details """
+    try:
+        return func(*args, **kwargs)
+    except XenAPI.Failure, exc:
+        logging.debug("Got exception: %s", exc)
+        if (len(exc.details) == 4 and
+            exc.details[0] == 'XENAPI_PLUGIN_EXCEPTION' and
+            exc.details[2] == 'Failure'):
+            params = None
+            try:
+                params = eval(exc.details[3])
+            except:
+                raise exc
+            raise XenAPI.Failure(params)
+        else:
+            raise
+    except xmlrpclib.ProtocolError, exc:
+        logging.debug("Got exception: %s", exc)
+        raise
+
+
+def _parse_xmlrpc_value(val):
+    """Parse the given value as if it were an XML-RPC value.  This is
+    sometimes used as the format for the task.result field."""
+    if not val:
+        return val
+    x = xmlrpclib.loads(
+        '<?xml version="1.0"?><methodResponse><params><param>' +
+        val +
+        '</param></params></methodResponse>')
+    return x[0][0]