#============================================================================ # 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 # 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': , '669df3b8-62be-4e61-800b-bbe8ee63a760': } } will turn into: norwich Test Xen Host 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 {} 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()