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# -*- coding: utf-8 -*-
# dbwrapper.py
# Copyright (C) 2013 LEAP
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Thread-safe wrapper for sqlite/pysqlcipher.
*TODO*
At some point we surely will want to switch to a twisted way of dealing
with this, using defers and proper callbacks. But I had this tested for
some time so postponing that refactor.
"""
import logging
import threading
import Queue
import time
import exceptions
from functools import partial
from leap.soledad.client import sqlcipher
logger = logging.getLogger(__name__)
class SQLCipherWrapper(threading.Thread):
def __init__(self, *args, **kwargs):
"""
Initializes a wrapper that proxies method and attribute
access to an underlying SQLCipher instance. We instantiate sqlcipher
in a thread, and all method accesses communicate with it using a
Queue.
:param *args: position arguments to pass to pysqlcipher initialization
:type args: tuple
:param **kwargs: keyword arguments to pass to pysqlcipher
initialization
:type kwargs: dict
"""
threading.Thread.__init__(self)
self._db = None
self._wrargs = args, kwargs
self._queue = Queue.Queue()
self._stopped = threading.Event()
self.start()
def _init_db(self):
"""
Initializes sqlcipher database.
This is called on a separate thread.
"""
# instantiate u1db
args, kwargs = self._wrargs
self._db = sqlcipher.open(*args, **kwargs)
def run(self):
"""
Main loop for the sqlcipher thread.
"""
logger.debug("SQLCipherWrapper thread started.")
logger.debug("Initializing sqlcipher")
end_mths = ("__end_thread", "_SQLCipherWrapper__end_thread")
self._init_db()
self._lock = threading.Lock()
ct = 0
started = False
while True:
if self._db is None:
if started:
break
if ct > 10:
break # XXX DEBUG
logger.debug('db not ready yet, waiting...')
time.sleep(1)
ct += 1
started = True
with self._lock:
try:
mth, q, wrargs = self._queue.get()
except:
logger.error("exception getting args from queue")
res = None
attr = getattr(self._db, mth, None)
if not attr:
if mth not in end_mths:
logger.error('method %s does not exist' % (mth,))
res = AttributeError(
"_db instance has no attribute %s" % mth)
elif callable(attr):
# invoke the method with the passed args
args = wrargs.get('args', [])
kwargs = wrargs.get('kwargs', {})
try:
res = attr(*args, **kwargs)
except Exception as e:
logger.error(
"Error on proxied method %s: '%r'." % (
attr, e))
res = e
else:
# non-callable attribute
res = attr
logger.debug('returning proxied db call...')
q.put(res)
if mth in end_mths:
logger.debug('ending thread')
break
logger.debug("SQLCipherWrapper thread terminated.")
self._stopped.set()
def close(self):
"""
Closes the sqlcipher database and finishes the thread. This method
should always be called explicitely.
"""
self.__getattr__('close')()
self.__end_thread()
def __getattr__(self, attr):
"""
Returns _db proxied attributes.
"""
def __proxied_mth(method, *args, **kwargs):
if not self._stopped.isSet():
wrargs = {'args': args, 'kwargs': kwargs}
q = Queue.Queue()
self._queue.put((method, q, wrargs))
res = q.get()
q.task_done()
if isinstance(res, exceptions.BaseException):
# XXX should get the original bt
raise res
return res
else:
logger.warning("tried to call proxied meth "
"but stopped is set: %s" %
(method,))
rgetattr = object.__getattribute__
if attr != "_db":
proxied = partial(__proxied_mth, attr)
return proxied
# fallback to regular behavior
return rgetattr(self, attr)
def __del__(self):
"""
Do not trust this get called. No guarantees given. Because of a funny
dance with the refs and the way the gc works, we should be calling the
close method explicitely.
"""
self.close()
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