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prevent synchronization of identical folders from multiple threads

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Use a mutex to lock the sync transaction, uniquely identified by the remote
folder name.

Serializing the syncs prevents any IDLE thread from syncing the same folder of
a concurrent autorefresh thread. Othewise, we could download new messages
twice, or read "one message past the last one" which in some cases creates a
duplicated messages.  Also prevents IDLE threads from reading new messages
before the autorefresh thread finishes synchronization.

Github-ref: #421
Originally-submitted-by: Michael Hohmuth <hohmuth@sax.de>
Signed-off-by: Nicolas Sebrecht <nicolas.s-dev@laposte.net>
This commit is contained in:
Nicolas Sebrecht 2017-02-27 19:01:42 +01:00
parent 04cb32bf9e
commit fc079499e9
1 changed files with 35 additions and 3 deletions
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38
offlineimap/accounts.py
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@ -15,7 +15,7 @@
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
from subprocess import Popen, PIPE
from threading import Event
from threading import Event, Lock
import os
import time
from sys import exc_info
@ -29,6 +29,9 @@ from offlineimap.ui import getglobalui
from offlineimap.threadutil import InstanceLimitedThread
FOLDER_NAMESPACE = 'LIMITED_FOLDER_'
# Key: account name, Value: Dict of Key: remotefolder name, Value: lock.
SYNC_MUTEXES = {}
SYNC_MUTEXES_LOCK = Lock()
try:
import fcntl
@ -430,11 +433,35 @@ class SyncableAccount(Account):
self.ui.error(e, exc_info()[2], msg="Calling hook")
#XXX: This function should likely be refactored. This should not be passed the
# account instance.
def syncfolder(account, remotefolder, quick):
"""Synchronizes given remote folder for the specified account.
Filtered folders on the remote side will not invoke this function. However,
this might be called in a concurrently."""
Filtered folders on the remote side will not invoke this function.
When called in concurrently for the same localfolder, syncs are
serialized."""
def acquire_mutex():
account_name = account.getname()
localfolder_name = localfolder.getfullname()
with SYNC_MUTEXES_LOCK:
if SYNC_MUTEXES.get(account_name) is None:
SYNC_MUTEXES[account_name] = {}
# The localfolder full name is good to uniquely identify the sync
# transaction.
if SYNC_MUTEXES[account_name].get(localfolder_name) is None:
#XXX: This lock could be an external file lock so we can remove
# the lock at the account level.
SYNC_MUTEXES[account_name][localfolder_name] = Lock()
# Acquire the lock.
SYNC_MUTEXES[account_name][localfolder_name].acquire()
def release_mutex():
SYNC_MUTEXES[account.getname()][localfolder.getfullname()].release()
def check_uid_validity():
# If either the local or the status folder has messages and
@ -528,6 +555,9 @@ def syncfolder(account, remotefolder, quick):
# Load local folder.
localfolder = account.get_local_folder(remotefolder)
# Acquire the mutex to start syncing.
acquire_mutex()
# Add the folder to the mbnames mailboxes.
mbnames.add(account.name, localrepos.getlocalroot(),
localfolder.getname())
@ -616,3 +646,5 @@ def syncfolder(account, remotefolder, quick):
if folder in locals():
locals()[folder].dropmessagelistcache()
statusfolder.closefiles()
# Release the mutex of this sync transaction.
release_mutex()