From 3c42913120a83d790dd29646b8ff516c6f58ebf7 Mon Sep 17 00:00:00 2001 From: Nicolas Sebrecht Date: Mon, 25 Jul 2016 14:39:11 +0200 Subject: [PATCH] sqlite: properly serialize operations on the databases 1. There is one database per folder and sqlite requires to serialize the writings. Instead of locking at LocalStatusSQLiteFolder instance 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 677afb8d8f4b3d41e38 is wrong because the same lock is shared for all the database files. Github-fix: https://github.com/OfflineIMAP/offlineimap/issues/350 Signed-off-by: Nicolas Sebrecht --- offlineimap/accounts.py | 14 ++-- offlineimap/folder/LocalStatusSQLite.py | 91 ++++++++++++++++--------- offlineimap/repository/LocalStatus.py | 1 + 3 files changed, 66 insertions(+), 40 deletions(-) diff --git a/offlineimap/accounts.py b/offlineimap/accounts.py index 2871be5..2dc288d 100644 --- a/offlineimap/accounts.py +++ b/offlineimap/accounts.py @@ -425,7 +425,8 @@ class SyncableAccount(Account): def syncfolder(account, remotefolder, quick): """Synchronizes given remote folder for the specified account. - Filtered folders on the remote side will not invoke this function.""" + Filtered folders on the remote side will not invoke this function. However, + this might be called in a concurrently.""" def check_uid_validity(localfolder, remotefolder, statusfolder): # If either the local or the status folder has messages and @@ -454,7 +455,7 @@ def syncfolder(account, remotefolder, quick): fd.close() def cachemessagelists_upto_date(localfolder, remotefolder, date): - """ Returns messages with uid > min(uids of messages newer than date).""" + """Returns messages with uid > min(uids of messages newer than date).""" localfolder.cachemessagelist(min_date=date) check_uid_validity(localfolder, remotefolder, statusfolder) @@ -474,7 +475,7 @@ def syncfolder(account, remotefolder, quick): min_date=time.gmtime(time.mktime(date) + 24*60*60)) def cachemessagelists_startdate(new, partial, date): - """ Retrieve messagelists when startdate has been set for + """Retrieve messagelists when startdate has been set for the folder 'partial'. Idea: suppose you want to clone the messages after date in one @@ -489,8 +490,7 @@ def syncfolder(account, remotefolder, quick): might not correspond. But, if we're cloning a folder into a new one, [min_uid, ...] does correspond to [1, ...]. - This is just for IMAP-IMAP. For Maildir-IMAP, use maxage instead. - """ + This is just for IMAP-IMAP. For Maildir-IMAP, use maxage instead.""" new.cachemessagelist() min_uid = partial.retrieve_min_uid() @@ -602,8 +602,8 @@ def syncfolder(account, remotefolder, quick): if e.severity > OfflineImapError.ERROR.FOLDER: raise else: - ui.error(e, exc_info()[2], msg = "Aborting sync, folder '%s' " - "[acc: '%s']" % (localfolder, account)) + ui.error(e, exc_info()[2], msg="Aborting sync, folder '%s' " + "[acc: '%s']"% (localfolder, account)) except Exception as e: ui.error(e, msg = "ERROR in syncfolder for %s folder %s: %s"% (account, remotefolder.getvisiblename(), traceback.format_exc())) diff --git a/offlineimap/folder/LocalStatusSQLite.py b/offlineimap/folder/LocalStatusSQLite.py index e2478b4..5899a48 100644 --- a/offlineimap/folder/LocalStatusSQLite.py +++ b/offlineimap/folder/LocalStatusSQLite.py @@ -16,13 +16,39 @@ # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA import os -import six import sqlite3 as sqlite from sys import exc_info from threading import Lock +import six + from .Base import BaseFolder +class DatabaseFileLock(object): + """Lock at database file level.""" + + def __init__(self): + self._lock = Lock() + self._counter = 0 + + def __enter__(self): + self._lock.acquire() + + def __exit__(self, typ, value, tb): + self._lock.release() + + def registerNewUser(self): + self._counter += 1 + + def removeOneUser(self): + self._counter -= 1 + + def getLock(self): + return self._lock + + def shouldClose(self): + return self._counter < 1 + class LocalStatusSQLiteFolder(BaseFolder): """LocalStatus backend implemented with an SQLite database @@ -42,11 +68,10 @@ class LocalStatusSQLiteFolder(BaseFolder): # Current version of our db format. cur_version = 2 # Keep track on how many threads need access to the database. - threads_open_count = 0 - threads_open_lock = Lock() + locks = {} # Key: filename, value: DatabaseFileLock instance. def __init__(self, name, repository): - self.sep = '.' # Needs to be set before super.__init__() + self.sep = '.' # Needs to be set before super().__init__(). super(LocalStatusSQLiteFolder, self).__init__(name, repository) self.root = repository.root self.filename = os.path.join(self.getroot(), self.getfolderbasename()) @@ -60,19 +85,24 @@ class LocalStatusSQLiteFolder(BaseFolder): raise UserWarning("SQLite database path '%s' is not a directory."% dirname) + self.connection = None # This lock protects against concurrent writes in same connection. self._dblock = Lock() - self.connection = None def openfiles(self): - # Protect the creation/upgrade of database accross threads. - with LocalStatusSQLiteFolder.threads_open_lock: - # Try to establish connection, no need for threadsafety in __init__. + # Make sure sqlite is in multithreading SERIALIZE mode. + assert sqlite.threadsafety == 1, 'Your sqlite is not multithreading safe.' + # Protect the creation/upgrade of database accross threads. + if self.filename not in LocalStatusSQLiteFolder.locks: + LocalStatusSQLiteFolder.locks[self.filename] = DatabaseFileLock() + databaseFileLock = LocalStatusSQLiteFolder.locks[self.filename] + with databaseFileLock.getLock(): + # Try to establish connection, no need for threadsafety in __init__. try: self.connection = sqlite.connect(self.filename, check_same_thread=False) - LocalStatusSQLiteFolder.threads_open_count += 1 + databaseFileLock.registerNewUser() except sqlite.OperationalError as e: # Operation had failed. six.reraise(UserWarning, @@ -83,9 +113,6 @@ class LocalStatusSQLiteFolder(BaseFolder): (self.filename, e)), exc_info()[2]) - # Make sure sqlite is in multithreading SERIALIZE mode. - assert sqlite.threadsafety == 1, 'Your sqlite is not multithreading safe.' - # Test if db version is current enough and if db is readable. try: cursor = self.connection.execute( @@ -118,32 +145,32 @@ class LocalStatusSQLiteFolder(BaseFolder): def isnewfolder(self): return self._newfolder - def __sql_write(self, sql, vars=None, executemany=False): + def __sql_write(self, sql, args=None, executemany=False): """Execute some SQL, retrying if the db was locked. :param sql: the SQL string passed to execute() - :param vars: the variable values to `sql`. E.g. (1,2) or {uid:1, + :param args: the variable values to `sql`. E.g. (1,2) or {uid:1, flags:'T'}. See sqlite docs for possibilities. :param executemany: bool indicating whether we want to perform conn.executemany() or conn.execute(). - :returns: the Cursor() or raises an Exception""" + :returns: None or raises an Exception.""" success = False while not success: - self._dblock.acquire() try: - if vars is None: - if executemany: - cursor = self.connection.executemany(sql) + with LocalStatusSQLiteFolder.locks[self.filename].getLock(): + if args is None: + if executemany: + self.connection.executemany(sql) + else: + self.connection.execute(sql) else: - cursor = self.connection.execute(sql) - else: - if executemany: - cursor = self.connection.executemany(sql, vars) - else: - cursor = self.connection.execute(sql, vars) - success = True - self.connection.commit() + if executemany: + self.connection.executemany(sql, args) + else: + self.connection.execute(sql, args) + success = True + self.connection.commit() except sqlite.OperationalError as e: if e.args[0] == 'cannot commit - no transaction is active': pass @@ -152,9 +179,6 @@ class LocalStatusSQLiteFolder(BaseFolder): success = False else: raise - finally: - self._dblock.release() - return cursor def __upgrade_db(self, from_ver): """Upgrade the sqlite format from version 'from_ver' to current""" @@ -229,9 +253,10 @@ class LocalStatusSQLiteFolder(BaseFolder): self.messagelist[uid]['mtime'] = row[2] def closefiles(self): - with LocalStatusSQLiteFolder.threads_open_lock: - LocalStatusSQLiteFolder.threads_open_count -= 1 - if self.threads_open_count < 1: + databaseFileLock = LocalStatusSQLiteFolder.locks[self.filename] + with databaseFileLock.getLock(): + databaseFileLock.removeOneUser() + if databaseFileLock.shouldClose(): try: self.connection.close() except: diff --git a/offlineimap/repository/LocalStatus.py b/offlineimap/repository/LocalStatus.py index becbda2..f23020f 100644 --- a/offlineimap/repository/LocalStatus.py +++ b/offlineimap/repository/LocalStatus.py @@ -95,6 +95,7 @@ class LocalStatusRepository(BaseRepository): # data. This might happen if the user removed the folder (maildir) and # it is re-created afterwards. folder.purge() + folder.openfiles() folder.save() folder.closefiles()