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