038a433f69
1. There is one database per folder and sqlite requires to serialize the
writings. Instead of locking at LocalStatusSQLiteFolder object level, introduce
a new DatabaseFileLock object which is shared across threads. This fixes the
concurrent writes issues that some users might experience by duplications or
flags restored to the previous state.
2. Close the database only when we are sure no other threads will use the
connection on a *per-file* basis. Previous fix 677afb8d8f is wrong
because the same lock is shared for all the databases.
Github-fix: https://github.com/OfflineIMAP/offlineimap/issues/350
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>
450 lines
17 KiB
Python
450 lines
17 KiB
Python
# Local status cache virtual folder: SQLite backend
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# Copyright (C) 2009-2011 Stewart Smith and contributors
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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 General Public License as published by
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# the Free Software Foundation; either version 2 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 General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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import os
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import sqlite3 as sqlite
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from sys import exc_info
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from threading import Lock
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try:
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import sqlite3 as sqlite
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except:
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pass #fail only if needed later on, not on import
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import six
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from .Base import BaseFolder
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class DatabaseFileLock(object):
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"""Lock at database file level."""
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def __init__(self):
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self._lock = Lock()
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self._counter = 0
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def __enter__(self):
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self._lock.acquire()
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def __exit__(self, typ, value, tb):
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self._lock.release()
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def registerNewUser(self):
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self._counter += 1
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def removeOneUser(self):
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self._counter -= 1
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def getLock(self):
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return self._lock
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def shouldClose(self):
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return self._counter < 1
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class LocalStatusSQLiteFolder(BaseFolder):
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"""LocalStatus backend implemented with an SQLite database
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As python-sqlite currently does not allow to access the same sqlite
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objects from various threads, we need to open get and close a db
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connection and cursor for all operations. This is a big disadvantage
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and we might want to investigate if we cannot hold an object open
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for a thread somehow."""
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# Though. According to sqlite docs, you need to commit() before
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# the connection is closed or your changes will be lost!
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# get db connection which autocommits
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# connection = sqlite.connect(self.filename, isolation_level=None)
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# cursor = connection.cursor()
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# return connection, cursor
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# Current version of our db format.
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cur_version = 2
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# Keep track on how many threads need access to the database.
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locks = {} # Key: filename, value: DatabaseFileLock instance.
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def __init__(self, name, repository):
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self.sep = '.' # Needs to be set before super().__init__().
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super(LocalStatusSQLiteFolder, self).__init__(name, repository)
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self.root = repository.root
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self.filename = os.path.join(self.getroot(), self.getfolderbasename())
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self.messagelist = {}
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self._newfolder = False # Flag if the folder is new.
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dirname = os.path.dirname(self.filename)
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if not os.path.exists(dirname):
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os.makedirs(dirname)
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if not os.path.isdir(dirname):
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raise UserWarning("SQLite database path '%s' is not a directory."%
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dirname)
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self.connection = None
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# This lock protects against concurrent writes in same connection.
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self._dblock = Lock()
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def openfiles(self):
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# Make sure sqlite is in multithreading SERIALIZE mode.
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assert sqlite.threadsafety == 1, 'Your sqlite is not multithreading safe.'
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# Protect the creation/upgrade of database accross threads.
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if self.filename not in LocalStatusSQLiteFolder.locks:
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LocalStatusSQLiteFolder.locks[self.filename] = DatabaseFileLock()
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databaseFileLock = LocalStatusSQLiteFolder.locks[self.filename]
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with databaseFileLock.getLock():
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# Try to establish connection, no need for threadsafety in __init__.
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try:
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self.connection = sqlite.connect(self.filename,
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check_same_thread=False)
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databaseFileLock.registerNewUser()
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except sqlite.OperationalError as e:
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# Operation had failed.
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raise UserWarning("cannot open database file '%s': %s.\nYou might "
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"want to check the rights to that file and if it cleanly opens "
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"with the 'sqlite<3>' command."%
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(self.filename, e)), None, exc_info()[2]
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# Test if db version is current enough and if db is readable.
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try:
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cursor = self.connection.execute(
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"SELECT value from metadata WHERE key='db_version'")
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except sqlite.DatabaseError:
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# db file missing or corrupt, recreate it.
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self.__create_db()
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else:
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# Fetch db version and upgrade if needed.
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version = int(cursor.fetchone()[0])
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if version < LocalStatusSQLiteFolder.cur_version:
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self.__upgrade_db(version)
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def storesmessages(self):
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return False
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def getfullname(self):
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return self.filename
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# Interface from LocalStatusFolder
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def isnewfolder(self):
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return self._newfolder
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# Interface from LocalStatusFolder
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def deletemessagelist(self):
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"""Delete all messages in the db."""
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self.__sql_write('DELETE FROM status')
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def __sql_write(self, sql, args=None, executemany=False):
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"""Execute some SQL, retrying if the db was locked.
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:param sql: the SQL string passed to execute()
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:param args: the variable values to `sql`. E.g. (1,2) or {uid:1,
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flags:'T'}. See sqlite docs for possibilities.
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:param executemany: bool indicating whether we want to
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perform conn.executemany() or conn.execute().
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:returns: None or raises an Exception."""
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success = False
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while not success:
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try:
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with LocalStatusSQLiteFolder.locks[self.filename].getLock():
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if args is None:
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if executemany:
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self.connection.executemany(sql)
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else:
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self.connection.execute(sql)
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else:
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if executemany:
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self.connection.executemany(sql, args)
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else:
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self.connection.execute(sql, args)
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success = True
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self.connection.commit()
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except sqlite.OperationalError as e:
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if e.args[0] == 'cannot commit - no transaction is active':
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pass
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elif e.args[0] == 'database is locked':
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self.ui.debug('', "Locked sqlite database, retrying.")
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success = False
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else:
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raise
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def __upgrade_db(self, from_ver):
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"""Upgrade the sqlite format from version 'from_ver' to current"""
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if self.connection is not None:
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self.connection.close() # Close old connections first.
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self.connection = sqlite.connect(self.filename,
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check_same_thread = False)
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# Upgrade from database version 1 to version 2
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# This change adds labels and mtime columns, to be used by Gmail IMAP and Maildir folders.
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if from_ver <= 1:
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self.ui._msg('Upgrading LocalStatus cache from version 1 to version 2 for %s:%s'%
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(self.repository, self))
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self.connection.executescript("""ALTER TABLE status ADD mtime INTEGER DEFAULT 0;
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ALTER TABLE status ADD labels VARCHAR(256) DEFAULT '';
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UPDATE metadata SET value='2' WHERE key='db_version';
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""")
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self.connection.commit()
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# Future version upgrades come here...
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# if from_ver <= 2: ... #upgrade from 2 to 3
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# if from_ver <= 3: ... #upgrade from 3 to 4
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def __create_db(self):
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"""Create a new db file.
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self.connection must point to the opened and valid SQlite
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database connection."""
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self.ui._msg('Creating new Local Status db for %s:%s'%
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(self.repository, self))
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self.connection.executescript("""
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CREATE TABLE metadata (key VARCHAR(50) PRIMARY KEY, value VARCHAR(128));
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INSERT INTO metadata VALUES('db_version', '2');
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CREATE TABLE status (id INTEGER PRIMARY KEY, flags VARCHAR(50), mtime INTEGER, labels VARCHAR(256));
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""")
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self.connection.commit()
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self._newfolder = True
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# Interface from BaseFolder
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def msglist_item_initializer(self, uid):
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return {'uid': uid, 'flags': set(), 'labels': set(), 'time': 0, 'mtime': 0}
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# Interface from BaseFolder
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def cachemessagelist(self):
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self.messagelist = {}
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cursor = self.connection.execute('SELECT id,flags,mtime,labels from status')
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for row in cursor:
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uid = row[0]
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self.messagelist[uid] = self.msglist_item_initializer(uid)
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flags = set(row[1])
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try:
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labels = set([lb.strip() for lb in
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row[3].split(',') if len(lb.strip()) > 0])
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except AttributeError:
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# FIXME: This except clause was introduced because row[3] from
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# database can be found of unexpected type NoneType. See
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# https://github.com/OfflineIMAP/offlineimap/issues/103
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#
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# We are fixing the type here but this would require more
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# researches to find the true root cause. row[3] is expected to
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# be a (empty) string, not None.
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#
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# Also, since database might return None, we have to fix the
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# database, too.
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labels = set()
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self.messagelist[uid]['flags'] = flags
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self.messagelist[uid]['labels'] = labels
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self.messagelist[uid]['mtime'] = row[2]
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def closefiles(self):
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databaseFileLock = LocalStatusSQLiteFolder.locks[self.filename]
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with databaseFileLock.getLock():
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databaseFileLock.removeOneUser()
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if databaseFileLock.shouldClose():
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try:
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self.connection.close()
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except:
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pass
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def dropmessagelistcache(self):
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self.messagelist = {}
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# Interface from LocalStatusFolder
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def save(self):
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pass
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# Noop. every transaction commits to database!
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def saveall(self):
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"""Saves the entire messagelist to the database."""
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data = []
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for uid, msg in self.messagelist.items():
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mtime = msg['mtime']
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flags = ''.join(sorted(msg['flags']))
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labels = ', '.join(sorted(msg['labels']))
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data.append((uid, flags, mtime, labels))
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self.__sql_write('INSERT OR REPLACE INTO status '
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'(id,flags,mtime,labels) VALUES (?,?,?,?)',
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data, executemany=True)
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# Following some pure SQLite functions, where we chose to use
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# BaseFolder() methods instead. Doing those on the in-memory list is
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# quicker anyway. If our db becomes so big that we don't want to
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# maintain the in-memory list anymore, these might come in handy
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# in the future though.
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#
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#def uidexists(self,uid):
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# conn, cursor = self.get_cursor()
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# with conn:
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# cursor.execute('SELECT id FROM status WHERE id=:id',{'id': uid})
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# return cursor.fetchone()
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# This would be the pure SQLite solution, use BaseFolder() method,
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# to avoid threading with sqlite...
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#def getmessageuidlist(self):
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# conn, cursor = self.get_cursor()
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# with conn:
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# cursor.execute('SELECT id from status')
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# r = []
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# for row in cursor:
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# r.append(row[0])
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# return r
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#def getmessagecount(self):
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# conn, cursor = self.get_cursor()
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# with conn:
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# cursor.execute('SELECT count(id) from status');
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# return cursor.fetchone()[0]
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#def getmessageflags(self, uid):
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# conn, cursor = self.get_cursor()
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# with conn:
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# cursor.execute('SELECT flags FROM status WHERE id=:id',
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# {'id': uid})
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# for row in cursor:
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# flags = [x for x in row[0]]
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# return flags
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# assert False,"getmessageflags() called on non-existing message"
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# Interface from BaseFolder
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def getmessagelist(self):
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return self.messagelist
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# Interface from BaseFolder
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def savemessage(self, uid, content, flags, rtime, mtime=0, labels=set()):
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"""Writes a new message, with the specified uid.
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See folder/Base for detail. Note that savemessage() does not
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check against dryrun settings, so you need to ensure that
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savemessage is never called in a dryrun mode."""
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if uid < 0:
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# We cannot assign a uid.
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return uid
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if self.uidexists(uid): # already have it
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self.savemessageflags(uid, flags)
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return uid
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self.messagelist[uid] = self.msglist_item_initializer(uid)
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self.messagelist[uid] = {'uid': uid, 'flags': flags, 'time': rtime, 'mtime': mtime, 'labels': labels}
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flags = ''.join(sorted(flags))
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labels = ', '.join(sorted(labels))
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self.__sql_write('INSERT INTO status (id,flags,mtime,labels) VALUES (?,?,?,?)',
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(uid,flags,mtime,labels))
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return uid
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# Interface from BaseFolder
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def savemessageflags(self, uid, flags):
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assert self.uidexists(uid)
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self.messagelist[uid]['flags'] = flags
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flags = ''.join(sorted(flags))
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self.__sql_write('UPDATE status SET flags=? WHERE id=?',(flags,uid))
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def getmessageflags(self, uid):
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return self.messagelist[uid]['flags']
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def savemessagelabels(self, uid, labels, mtime=None):
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self.messagelist[uid]['labels'] = labels
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if mtime: self.messagelist[uid]['mtime'] = mtime
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labels = ', '.join(sorted(labels))
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if mtime:
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self.__sql_write('UPDATE status SET labels=?, mtime=? WHERE id=?',(labels,mtime,uid))
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else:
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self.__sql_write('UPDATE status SET labels=? WHERE id=?',(labels,uid))
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def savemessageslabelsbulk(self, labels):
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"""
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Saves labels from a dictionary in a single database operation.
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"""
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data = [(', '.join(sorted(l)), uid) for uid, l in labels.items()]
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self.__sql_write('UPDATE status SET labels=? WHERE id=?', data, executemany=True)
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for uid, l in labels.items():
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self.messagelist[uid]['labels'] = l
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def addmessageslabels(self, uids, labels):
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data = []
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for uid in uids:
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newlabels = self.messagelist[uid]['labels'] | labels
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data.append((', '.join(sorted(newlabels)), uid))
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self.__sql_write('UPDATE status SET labels=? WHERE id=?', data, executemany=True)
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for uid in uids:
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self.messagelist[uid]['labels'] = self.messagelist[uid]['labels'] | labels
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def deletemessageslabels(self, uids, labels):
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data = []
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for uid in uids:
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newlabels = self.messagelist[uid]['labels'] - labels
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data.append((', '.join(sorted(newlabels)), uid))
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self.__sql_write('UPDATE status SET labels=? WHERE id=?', data, executemany=True)
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for uid in uids:
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self.messagelist[uid]['labels'] = self.messagelist[uid]['labels'] - labels
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def getmessagelabels(self, uid):
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return self.messagelist[uid]['labels']
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def savemessagesmtimebulk(self, mtimes):
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"""Saves mtimes from the mtimes dictionary in a single database operation."""
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data = [(mt, uid) for uid, mt in mtimes.items()]
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self.__sql_write('UPDATE status SET mtime=? WHERE id=?', data, executemany=True)
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for uid, mt in mtimes.items():
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self.messagelist[uid]['mtime'] = mt
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def getmessagemtime(self, uid):
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return self.messagelist[uid]['mtime']
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# Interface from BaseFolder
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def deletemessage(self, uid):
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if not uid in self.messagelist:
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return
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self.__sql_write('DELETE FROM status WHERE id=?', (uid, ))
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del(self.messagelist[uid])
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# Interface from BaseFolder
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def deletemessages(self, uidlist):
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"""Delete list of UIDs from status cache
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This function uses sqlites executemany() function which is
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much faster than iterating through deletemessage() when we have
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many messages to delete."""
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# Weed out ones not in self.messagelist
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uidlist = [uid for uid in uidlist if uid in self.messagelist]
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if not len(uidlist):
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return
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# arg2 needs to be an iterable of 1-tuples [(1,),(2,),...]
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self.__sql_write('DELETE FROM status WHERE id=?', zip(uidlist, ), True)
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for uid in uidlist:
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del(self.messagelist[uid])
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