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Konrad Rzeszutek Wilk
e8d40584e5
Bugzilla 1680: Xend fails to start if /var/lib/xend/state/*.xml are empty which I get often when replacing the Xen hypervisor with a newer version. This can be easily be reproduced under Fedora Core 16 by installing xen RPMs and then replacing the xen.gz with a newer version. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Signed-off-by: Anthony Low <shinji@pikopiko.org> Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>
235 lines
8.8 KiB
Python
235 lines
8.8 KiB
Python
#============================================================================
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of version 2.1 of the GNU Lesser General Public
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# License as published by the Free Software Foundation.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#============================================================================
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# Copyright (C) 2004, 2005 Mike Wray <mike.wray@hp.com>
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# Copyright (c) 2006 Xensource Inc.
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#============================================================================
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import os
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from xen.xend import uuid
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from xen.xend.XendLogging import log
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from xml.dom import minidom
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from xml.dom import Node
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class XendStateStore:
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"""Manages persistent storage of Xend's internal state, mainly
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relating to API objects.
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It stores objects atomically in the file system as flat XML files
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categorised by their 'class'.
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For example:
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/var/lib/xend/state/cpu.xml will contain the host cpu state
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/var/lib/xend/state/sr.xml will contain the storage repository state.
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For the application, it will load the state via this class:
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load_state('cpu') will return a marshalled dictionary object
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containing the cpu state.
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save_state('cpu', dict) will save the state contained in the dictionary
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object about the 'cpu'.
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The state is stored where each top level element has a UUID in its
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attributes. eg:
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host['49c01812-3c28-1ad4-a59d-2a3f81b13ec2'] = {
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'name': 'norwich',
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'desc': 'Test Xen Host',
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'cpu': {'6fc2d1ed-7eb0-4c9d-8006-3657d5483ae0': <obj>,
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'669df3b8-62be-4e61-800b-bbe8ee63a760': <obj>}
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}
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will turn into:
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<hosts>
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<host uuid='49c01812-3c28-1ad4-a59d-2a3f81b13ec2'>
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<name type='string'>norwich</name>
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<description type='string'>Test Xen Host</description>
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<cpu type='dict'>
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<item uuid='6fc2d1ed-7eb0-4c9d-8006-3657d5483ae0' />
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<item uuid='669df3b8-62be-4e61-800b-bbe8ee63a760' />
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</cpu>
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</host>
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</hosts>
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Note that it only dumps one level, so the references to CPU are
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stored in a separate file.
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"""
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def __init__(self, base = "/var/lib/xend/state"):
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self.base = base
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if not os.path.exists(self.base):
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os.makedirs(self.base)
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def _xml_file(self, cls):
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"""Return the absolute filename of the XML state storage file.
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@param cls: name of the class.
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@type cls: string
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@rtype: string
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@return absolute filename of XML file to write/read from.
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"""
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return os.path.join(self.base, '%s.xml' % cls)
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def load_state(self, cls):
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"""Load the saved state of a class from persistent XML storage.
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References loaded from the XML will just point to an empty
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dictionary which the caller will need to replace manually.
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@param cls: name of the class to load.
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@type cls: string
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@rtype: dict
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"""
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xml_path = self._xml_file(cls)
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if not os.path.exists(xml_path):
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return {}
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if not os.path.getsize(xml_path) == 0:
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return {}
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dom = minidom.parse(xml_path)
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root = dom.documentElement
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state = {}
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for child in root.childNodes:
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if child.nodeType != Node.ELEMENT_NODE:
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continue # skip non element nodes
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uuid = child.getAttribute('uuid').encode('utf8')
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cls_dict = {}
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for val_elem in child.childNodes:
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if val_elem.nodeType != Node.ELEMENT_NODE:
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continue # skip non element nodes
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val_name = val_elem.tagName
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val_type = val_elem.getAttribute('type').encode('utf8')
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val_uuid = val_elem.getAttribute('uuid').encode('utf8')
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val_elem.normalize()
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val_text = ''
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if val_elem.firstChild:
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val_text = val_elem.firstChild.nodeValue.strip()
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if val_type == 'list':
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cls_dict[val_name] = []
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for item in val_elem.childNodes:
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if item.nodeType != Node.ELEMENT_NODE:
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continue # skip non element nodes
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cls_dict[val_name].append(item.getAttribute('uuid'))
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elif val_type == 'dict':
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cls_dict[val_name] = {}
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for item in val_elem.childNodes:
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if item.nodeType != Node.ELEMENT_NODE:
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continue # skip non element nodes
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k = item.getAttribute('key').encode('utf8')
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v = item.getAttribute('value').encode('utf8')
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cls_dict[val_name][k] = v
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elif val_type == 'string':
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cls_dict[val_name] = val_text.encode('utf8')
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elif val_type == 'float':
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cls_dict[val_name] = float(val_text)
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elif val_type == 'int':
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cls_dict[val_name] = int(val_text)
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elif val_type == 'bool':
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cls_dict[val_name] = bool(int(val_text))
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state[uuid] = cls_dict
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dom.unlink()
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return state
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def save_state(self, cls, state):
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"""Save a Xen API record struct into an XML persistent storage
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for future loading when Xend restarts.
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If we encounter a dictionary or a list, we only store the
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keys because they are going to be UUID references to another
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object.
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@param cls: Class name (singular) of the record
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@type cls: string
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@param state: a Xen API struct of the state of the class.
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@type state: dict
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@rtype: None
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"""
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xml_path = self._xml_file(cls)
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doc = minidom.getDOMImplementation().createDocument(None,
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cls + 's',
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None)
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root = doc.documentElement
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# Marshall a dictionary into our custom XML file format.
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for uuid, info in state.items():
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node = doc.createElement(cls)
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root.appendChild(node)
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node.setAttribute('uuid', uuid)
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for key, val in info.items():
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store_val = val
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store_type = None
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# deal with basic types
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if type(val) in (str, unicode):
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store_val = val
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store_type = 'string'
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elif type(val) == int:
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store_val = str(val)
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store_type = 'int'
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elif type(val) == float:
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store_val = str(val)
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store_type = 'float'
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elif type(val) == bool:
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store_val = str(int(val))
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store_type = 'bool'
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if store_type is not None:
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val_node = doc.createElement(key)
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val_node.setAttribute('type', store_type)
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node.appendChild(val_node)
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# attach the value
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val_text = doc.createTextNode(store_val)
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val_node.appendChild(val_text)
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continue
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# deal with dicts and lists
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if type(val) == dict:
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val_node = doc.createElement(key)
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val_node.setAttribute('type', 'dict')
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for val_item in val.keys():
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tmp = doc.createElement("item")
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if key in ['other_config', 'device_config']:
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tmp.setAttribute('key', str(val_item))
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tmp.setAttribute('value', str(val[val_item]))
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else:
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tmp.setAttribute('uuid', val_uuid)
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val_node.appendChild(tmp)
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node.appendChild(val_node)
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elif type(val) in (list, tuple):
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val_node = doc.createElement(key)
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val_node.setAttribute('type', 'list')
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for val_uuid in val:
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tmp = doc.createElement("item")
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tmp.setAttribute('uuid', val_uuid)
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val_node.appendChild(tmp)
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node.appendChild(val_node)
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open(xml_path, 'w').write(doc.toprettyxml())
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doc.unlink()
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