172 lines
5.0 KiB
Python
172 lines
5.0 KiB
Python
# Nemubot is a smart and modulable IM bot.
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# Copyright (C) 2012-2015 Mercier Pierre-Olivier
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU Affero General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program 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
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# GNU Affero General Public License for more details.
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#
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# You should have received a copy of the GNU Affero General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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import fcntl
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import logging
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import os
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import xml.parsers.expat
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from nemubot.datastore.abstract import Abstract
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logger = logging.getLogger("nemubot.datastore.xml")
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class XML(Abstract):
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"""A concrete implementation of a data store that relies on XML files"""
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def __init__(self, basedir, rotate=True):
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"""Initialize the datastore
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Arguments:
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basedir -- path to directory containing XML files
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rotate -- auto-backup files?
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"""
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self.basedir = basedir
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self.rotate = rotate
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self.nb_save = 0
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def open(self):
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"""Lock the directory"""
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if not os.path.isdir(self.basedir):
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os.mkdir(self.basedir)
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lock_path = os.path.join(self.basedir, ".used_by_nemubot")
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self.lock_file = open(lock_path, 'a+')
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ok = True
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try:
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fcntl.lockf(self.lock_file, fcntl.LOCK_EX | fcntl.LOCK_NB)
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except OSError:
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ok = False
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if not ok:
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with open(lock_path, 'r') as lf:
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pid = lf.readline()
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raise Exception("Data dir already locked, by PID %s" % pid)
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self.lock_file.truncate()
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self.lock_file.write(str(os.getpid()))
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self.lock_file.flush()
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return True
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def close(self):
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"""Release a locked path"""
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if hasattr(self, "lock_file"):
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self.lock_file.close()
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lock_path = os.path.join(self.basedir, ".used_by_nemubot")
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if os.path.isdir(self.basedir) and os.path.exists(lock_path):
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os.unlink(lock_path)
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del self.lock_file
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return True
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return False
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def _get_data_file_path(self, module):
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"""Get the path to the module data file"""
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return os.path.join(self.basedir, module + ".xml")
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def load(self, module, knodes):
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"""Load data for the given module
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Argument:
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module -- the module name of data to load
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knodes -- the schema to use to load the datas
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"""
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data_file = self._get_data_file_path(module)
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if knodes is None:
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from nemubot.tools.xmlparser import parse_file
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def _true_load(path):
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return parse_file(path)
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else:
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from nemubot.tools.xmlparser import XMLParser
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p = XMLParser(knodes)
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def _true_load(path):
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return p.parse_file(path)
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# Try to load original file
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if os.path.isfile(data_file):
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try:
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return _true_load(data_file)
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except xml.parsers.expat.ExpatError:
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# Try to load from backup
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for i in range(10):
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path = data_file + "." + str(i)
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if os.path.isfile(path):
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try:
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cnt = _true_load(path)
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logger.warn("Restoring from backup: %s", path)
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return cnt
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except xml.parsers.expat.ExpatError:
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continue
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# Default case: initialize a new empty datastore
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return super().load(module, knodes)
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def _rotate(self, path):
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"""Backup given path
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Argument:
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path -- location of the file to backup
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"""
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self.nb_save += 1
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for i in range(10):
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if self.nb_save % (1 << i) == 0:
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src = path + "." + str(i-1) if i != 0 else path
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dst = path + "." + str(i)
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if os.path.isfile(src):
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os.rename(src, dst)
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def save(self, module, data):
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"""Load data for the given module
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Argument:
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module -- the module name of data to load
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data -- the new data to save
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"""
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path = self._get_data_file_path(module)
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if self.rotate:
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self._rotate(path)
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if data is None:
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return
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import tempfile
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_, tmpath = tempfile.mkstemp()
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with open(tmpath, "w") as f:
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import xml.sax.saxutils
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gen = xml.sax.saxutils.XMLGenerator(f, "utf-8")
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gen.startDocument()
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data.saveElement(gen)
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gen.endDocument()
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# Atomic save
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import shutil
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shutil.move(tmpath, path)
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