[bug] Sync Locking based on class + db file path

Change locking to be class based and each lock generated by db file
path.

2 files changed, 19 insertions, 9 deletions

diff --git a/client/src/leap/soledad/client/api.py b/client/src/leap/soledad/client/api.py
index 9000029f..633c07d0 100644
--- a/client/src/leap/soledad/client/api.py
+++ b/client/src/leap/soledad/client/api.py
@@ -41,13 +41,14 @@ except ImportError:
 from itertools import chain
 
 from StringIO import StringIO
+from collections import defaultdict
 from u1db.remote import http_client
 from u1db.remote.ssl_match_hostname import match_hostname
 from zope.interface import implements
 
 from leap.common.config import get_path_prefix
 from leap.common.plugins import collect_plugins
-from twisted.internet import defer
+from twisted.internet.defer import DeferredLock
 
 from leap.soledad.common import SHARED_DB_NAME
 from leap.soledad.common import soledad_assert
@@ -114,6 +115,7 @@ class Soledad(object):
     local_db_file_name = 'soledad.u1db'
     secrets_file_name = "soledad.json"
     default_prefix = os.path.join(get_path_prefix(), 'leap', 'soledad')
+    _syncing_lock = defaultdict(DeferredLock)
 
     def __init__(self, uuid, passphrase, secrets_path, local_db_path,
                  server_url, cert_file, shared_db=None,
@@ -200,7 +202,6 @@ class Soledad(object):
 
         self._crypto = SoledadCrypto(self._secrets.remote_storage_secret)
         self._init_u1db_sqlcipher_backend()
-        self.sync_lock = defer.DeferredLock()
 
         if syncable:
             self._init_u1db_syncer()
@@ -671,7 +672,7 @@ class Soledad(object):
         # -----------------------------------------------------------------
 
         sync_url = urlparse.urljoin(self._server_url, 'user-%s' % self.uuid)
-        d = self.sync_lock.run(lambda: self._dbsyncer.sync(
+        d = self.syncing_lock.run(lambda: self._dbsyncer.sync(
             sync_url,
             creds=self._creds,
             defer_decryption=defer_decryption))
@@ -706,6 +707,17 @@ class Soledad(object):
         return d
 
     @property
+    def syncing_lock(self):
+        """
+        Class based lock to ensure consistency on concurrent calls to sync.
+        Each lock is based on the path of db file.
+
+        :return: DeferredLock based on this instance path of db file
+        :rtype: DeferredLock
+        """
+        return self._syncing_lock[self._local_db_path]
+
+    @property
     def syncing(self):
         """
         Return wether Soledad is currently synchronizing with the server.
@@ -713,7 +725,7 @@ class Soledad(object):
         :return: Wether Soledad is currently synchronizing with the server.
         :rtype: bool
         """
-        return self.sync_lock.locked
+        return self.syncing_lock.locked
 
     def _set_token(self, token):
         """
diff --git a/client/src/leap/soledad/client/sqlcipher.py b/client/src/leap/soledad/client/sqlcipher.py
index 249ffb1a..6a4fa01a 100644
--- a/client/src/leap/soledad/client/sqlcipher.py
+++ b/client/src/leap/soledad/client/sqlcipher.py
@@ -420,11 +420,6 @@ class SQLCipherU1DBSync(SQLCipherDatabase):
     """
     ENCRYPT_LOOP_PERIOD = 1
 
-    """
-    A dictionary that hold locks which avoid multiple sync attempts from the
-    same database replica.
-    """
-
     def __init__(self, opts, soledad_crypto, replica_uid, cert_file,
                  defer_encryption=False, sync_db=None, sync_enc_pool=None):
 
@@ -513,6 +508,9 @@ class SQLCipherU1DBSync(SQLCipherDatabase):
         changes, we should add a thread-safe condition to ensure the db is
         ready before using it.
 
+        This method is atomic, with atomicity guaranteed by caller. Each
+        caller should implement a locking mechanism to ensure atomicity.
+
         :param url: The url of the target replica to sync with.
         :type url: str
         :param creds: optional dictionary giving credentials to authorize the