[refactor] separate SoledadBackend from CouchDatabase

CouchDatabase was renamed to SoledadBackend and a new class
CouchDatabase was created to hold all couchdb code. This should make
SoledadBackend less tied to database implementation. A few more
separations are needed to split into modules.

11 files changed, 706 insertions, 486 deletions

diff --git a/common/src/leap/soledad/common/couch.py b/common/src/leap/soledad/common/couch.py
index 4f569559..d4f67696 100644
--- a/common/src/leap/soledad/common/couch.py
+++ b/common/src/leap/soledad/common/couch.py
@@ -113,7 +113,7 @@ def couch_server(url):
 THREAD_POOL = ThreadPool(20)
 
 
-class CouchDatabase(CommonBackend):
+class SoledadBackend(CommonBackend):
 
     """
     A U1DB implementation that uses CouchDB as its persistence layer.
@@ -135,27 +135,13 @@ class CouchDatabase(CommonBackend):
         :type ensure_ddocs: bool
 
         :return: the database instance
-        :rtype: CouchDatabase
+        :rtype: SoledadBackend
         """
-        # get database from url
-        m = re.match('(^https?://[^/]+)/(.+)$', url)
-        if not m:
-            raise InvalidURLError
-        url = m.group(1)
-        dbname = m.group(2)
-        with couch_server(url) as server:
-            try:
-                server[dbname]
-            except ResourceNotFound:
-                if not create:
-                    raise DatabaseDoesNotExist()
-                server.create(dbname)
+        db = CouchDatabase.open_database(url, create, ensure_ddocs)
         return cls(
-            url, dbname, replica_uid=replica_uid,
-            ensure_ddocs=ensure_ddocs, database_security=database_security)
+            db, replica_uid=replica_uid)
 
-    def __init__(self, url, dbname, replica_uid=None, ensure_ddocs=False,
-                 database_security=None):
+    def __init__(self, database, replica_uid=None):
         """
         Create a new Couch data container.
 
@@ -169,25 +155,14 @@ class CouchDatabase(CommonBackend):
         :type ensure_ddocs: bool
         """
         # save params
-        self._url = url
-        self._session = Session(timeout=COUCH_TIMEOUT)
         self._factory = CouchDocument
         self._real_replica_uid = None
         # configure couch
-        self._dbname = dbname
-        self._database = Database(
-            urljoin(self._url, self._dbname),
-            self._session)
-        try:
-            self._database.info()
-        except ResourceNotFound:
-            raise DatabaseDoesNotExist()
+        self._cache = None
+        self._dbname = database._dbname
+        self._database = database
         if replica_uid is not None:
             self._set_replica_uid(replica_uid)
-        if ensure_ddocs:
-            self.ensure_ddocs_on_db()
-            self.ensure_security_ddoc(database_security)
-        self._cache = None
 
     @property
     def cache(self):
@@ -205,45 +180,6 @@ class CouchDatabase(CommonBackend):
         """
         self._cache = cache
 
-    def ensure_ddocs_on_db(self):
-        """
-        Ensure that the design documents used by the backend exist on the
-        couch database.
-        """
-        for ddoc_name in ['docs', 'syncs', 'transactions']:
-            try:
-                self._database.resource('_design',
-                                        ddoc_name, '_info').get_json()
-            except ResourceNotFound:
-                ddoc = json.loads(
-                    binascii.a2b_base64(
-                        getattr(ddocs, ddoc_name)))
-                self._database.save(ddoc)
-
-    def ensure_security_ddoc(self, security_config=None):
-        """
-        Make sure that only soledad user is able to access this database as
-        an unprivileged member, meaning that administration access will
-        be forbidden even inside an user database.
-        The goal is to make sure that only the lowest access level is given
-        to the unprivileged CouchDB user set on the server process.
-        This is achieved by creating a _security design document, see:
-        http://docs.couchdb.org/en/latest/api/database/security.html
-
-        :param database_security: security configuration parsed from conf file
-        :type cache: dict
-        """
-        security_config = security_config or {}
-        security = self._database.resource.get_json('_security')[2]
-        security['members'] = {'names': [], 'roles': []}
-        security['members']['names'] = security_config.get('members',
-                                                           ['soledad'])
-        security['members']['roles'] = security_config.get('members_roles', [])
-        security['admins'] = {'names': [], 'roles': []}
-        security['admins']['names'] = security_config.get('admins', [])
-        security['admins']['roles'] = security_config.get('admins_roles', [])
-        self._database.resource.put_json('_security', body=security)
-
     def get_sync_target(self):
         """
         Return a SyncTarget object, for another u1db to synchronize with.
@@ -257,8 +193,7 @@ class CouchDatabase(CommonBackend):
         """
         Delete a U1DB CouchDB database.
         """
-        with couch_server(self._url) as server:
-            del(server[self._dbname])
+        self._database.delete_database()
 
     def close(self):
         """
@@ -267,10 +202,7 @@ class CouchDatabase(CommonBackend):
         :return: True if db was succesfully closed.
         :rtype: bool
         """
-        self._url = None
-        self._full_commit = None
-        self._session = None
-        self._database = None
+        self._database.close()
         return True
 
     def __del__(self):
@@ -286,18 +218,9 @@ class CouchDatabase(CommonBackend):
         :param replica_uid: The new replica uid.
         :type replica_uid: str
         """
-        try:
-            # set on existent config document
-            doc = self._database['u1db_config']
-            doc['replica_uid'] = replica_uid
-        except ResourceNotFound:
-            # or create the config document
-            doc = {
-                '_id': 'u1db_config',
-                'replica_uid': replica_uid,
-            }
-        self._database.save(doc)
+        self._database.set_replica_uid(replica_uid)
         self._real_replica_uid = replica_uid
+        self.cache['replica_uid'] = self._real_replica_uid
 
     def _get_replica_uid(self):
         """
@@ -307,21 +230,13 @@ class CouchDatabase(CommonBackend):
         :rtype: str
         """
         if self._real_replica_uid is not None:
-            self.cache[self._url] = {'replica_uid': self._real_replica_uid}
-            return self._real_replica_uid
-        if self._url in self.cache:
-            return self.cache[self._url]['replica_uid']
-        try:
-            # grab replica_uid from server
-            doc = self._database['u1db_config']
-            self.cache[self._url] = doc
-            self._real_replica_uid = doc['replica_uid']
-            return self._real_replica_uid
-        except ResourceNotFound:
-            # create a unique replica_uid
-            self._real_replica_uid = uuid.uuid4().hex
-            self._set_replica_uid(self._real_replica_uid)
+            self.cache['replica_uid'] = self._real_replica_uid
             return self._real_replica_uid
+        if 'replica_uid' in self.cache:
+            return self.cache['replica_uid']
+        self._real_replica_uid = self._database.get_replica_uid()
+        self._set_replica_uid(self._real_replica_uid)
+        return self._real_replica_uid
 
     _replica_uid = property(_get_replica_uid, _set_replica_uid)
 
@@ -348,19 +263,7 @@ class CouchDatabase(CommonBackend):
                                              design document for an yet
                                              unknown reason.
         """
-        # query a couch list function
-        if self.replica_uid + '_gen' in self.cache:
-            return self.cache[self.replica_uid + '_gen']['generation']
-        ddoc_path = ['_design', 'transactions', '_list', 'generation', 'log']
-        res = self._database.resource(*ddoc_path)
-        try:
-            response = res.get_json()
-            self.cache[self.replica_uid + '_gen'] = response[2]
-            return response[2]['generation']
-        except ResourceNotFound as e:
-            raise_missing_design_doc_error(e, ddoc_path)
-        except ServerError as e:
-            raise_server_error(e, ddoc_path)
+        return self._get_generation_info()[0]
 
     def _get_generation_info(self):
         """
@@ -385,18 +288,10 @@ class CouchDatabase(CommonBackend):
         """
         if self.replica_uid + '_gen' in self.cache:
             response = self.cache[self.replica_uid + '_gen']
-            return (response['generation'], response['transaction_id'])
-        # query a couch list function
-        ddoc_path = ['_design', 'transactions', '_list', 'generation', 'log']
-        res = self._database.resource(*ddoc_path)
-        try:
-            response = res.get_json()
-            self.cache[self.replica_uid + '_gen'] = response[2]
-            return (response[2]['generation'], response[2]['transaction_id'])
-        except ResourceNotFound as e:
-            raise_missing_design_doc_error(e, ddoc_path)
-        except ServerError as e:
-            raise_server_error(e, ddoc_path)
+            return response
+        cur_gen, newest_trans_id = self._database._get_generation_info()
+        self.cache[self.replica_uid + '_gen'] = (cur_gen, newest_trans_id)
+        return (cur_gen, newest_trans_id)
 
     def _get_trans_id_for_gen(self, generation):
         """
@@ -408,37 +303,8 @@ class CouchDatabase(CommonBackend):
         :return: The transaction id for C{generation}.
         :rtype: str
 
-        :raise InvalidGeneration: Raised when the generation does not exist.
-        :raise MissingDesignDocError: Raised when tried to access a missing
-                                      design document.
-        :raise MissingDesignDocListFunctionError: Raised when trying to access
-                                                  a missing list function on a
-                                                  design document.
-        :raise MissingDesignDocNamedViewError: Raised when trying to access a
-                                               missing named view on a design
-                                               document.
-        :raise MissingDesignDocDeletedError: Raised when trying to access a
-                                             deleted design document.
-        :raise MissingDesignDocUnknownError: Raised when failed to access a
-                                             design document for an yet
-                                             unknown reason.
         """
-        if generation == 0:
-            return ''
-        # query a couch list function
-        ddoc_path = [
-            '_design', 'transactions', '_list', 'trans_id_for_gen', 'log'
-        ]
-        res = self._database.resource(*ddoc_path)
-        try:
-            response = res.get_json(gen=generation)
-            if response[2] == {}:
-                raise InvalidGeneration
-            return response[2]['transaction_id']
-        except ResourceNotFound as e:
-            raise_missing_design_doc_error(e, ddoc_path)
-        except ServerError as e:
-            raise_server_error(e, ddoc_path)
+        return self._database._get_trans_id_for_gen(generation)
 
     def _get_transaction_log(self):
         """
@@ -447,30 +313,8 @@ class CouchDatabase(CommonBackend):
         :return: The complete transaction log.
         :rtype: [(str, str)]
 
-        :raise MissingDesignDocError: Raised when tried to access a missing
-                                      design document.
-        :raise MissingDesignDocListFunctionError: Raised when trying to access
-                                                  a missing list function on a
-                                                  design document.
-        :raise MissingDesignDocNamedViewError: Raised when trying to access a
-                                               missing named view on a design
-                                               document.
-        :raise MissingDesignDocDeletedError: Raised when trying to access a
-                                             deleted design document.
-        :raise MissingDesignDocUnknownError: Raised when failed to access a
-                                             design document for an yet
-                                             unknown reason.
         """
-        # query a couch view
-        ddoc_path = ['_design', 'transactions', '_view', 'log']
-        res = self._database.resource(*ddoc_path)
-        try:
-            response = res.get_json()
-            return map(
-                lambda row: (row['id'], row['value']),
-                response[2]['rows'])
-        except ResourceNotFound as e:
-            raise_missing_design_doc_error(e, ddoc_path)
+        return self._database._get_transaction_log()
 
     def _get_doc(self, doc_id, check_for_conflicts=False):
         """
@@ -487,44 +331,7 @@ class CouchDatabase(CommonBackend):
         :return: The document.
         :rtype: CouchDocument
         """
-        # get document with all attachments (u1db content and eventual
-        # conflicts)
-        try:
-            result = \
-                self._database.resource(doc_id).get_json(
-                    attachments=True)[2]
-        except ResourceNotFound:
-            return None
-        return self.__parse_doc_from_couch(result, doc_id, check_for_conflicts)
-
-    def __parse_doc_from_couch(self, result, doc_id,
-                               check_for_conflicts=False):
-        # restrict to u1db documents
-        if 'u1db_rev' not in result:
-            return None
-        doc = self._factory(doc_id, result['u1db_rev'])
-        # set contents or make tombstone
-        if '_attachments' not in result \
-                or 'u1db_content' not in result['_attachments']:
-            doc.make_tombstone()
-        else:
-            doc.content = json.loads(
-                binascii.a2b_base64(
-                    result['_attachments']['u1db_content']['data']))
-        # determine if there are conflicts
-        if check_for_conflicts \
-                and '_attachments' in result \
-                and 'u1db_conflicts' in result['_attachments']:
-            doc.set_conflicts(
-                self._build_conflicts(
-                    doc.doc_id,
-                    json.loads(binascii.a2b_base64(
-                        result['_attachments']['u1db_conflicts']['data']))))
-        # store couch revision
-        doc.couch_rev = result['_rev']
-        # store transactions
-        doc.transactions = result['u1db_transactions']
-        return doc
+        return self._database._get_doc(doc_id, check_for_conflicts)
 
     def get_doc(self, doc_id, include_deleted=False):
         """
@@ -561,11 +368,7 @@ class CouchDatabase(CommonBackend):
             the documents in the database.
         :rtype: (int, [CouchDocument])
         """
-
-        generation = self._get_generation()
-        results = list(self.get_docs(self._database,
-                                     include_deleted=include_deleted))
-        return (generation, results)
+        return self._database.get_all_docs(include_deleted)
 
     def _put_doc(self, old_doc, doc):
         """
@@ -579,84 +382,15 @@ class CouchDatabase(CommonBackend):
         :type old_doc: CouchDocument
         :param doc: The document to be put.
         :type doc: CouchDocument
-
-        :raise RevisionConflict: Raised when trying to update a document but
-                                 couch revisions mismatch.
-        :raise MissingDesignDocError: Raised when tried to access a missing
-                                      design document.
-        :raise MissingDesignDocListFunctionError: Raised when trying to access
-                                                  a missing list function on a
-                                                  design document.
-        :raise MissingDesignDocNamedViewError: Raised when trying to access a
-                                               missing named view on a design
-                                               document.
-        :raise MissingDesignDocDeletedError: Raised when trying to access a
-                                             deleted design document.
-        :raise MissingDesignDocUnknownError: Raised when failed to access a
-                                             design document for an yet
-                                             unknown reason.
         """
-        attachments = {}  # we save content and conflicts as attachments
-        parts = []  # and we put it using couch's multipart PUT
-        # save content as attachment
-        if doc.is_tombstone() is False:
-            content = doc.get_json()
-            attachments['u1db_content'] = {
-                'follows': True,
-                'content_type': 'application/octet-stream',
-                'length': len(content),
-            }
-            parts.append(content)
-        # save conflicts as attachment
-        if doc.has_conflicts is True:
-            conflicts = json.dumps(
-                map(lambda cdoc: (cdoc.rev, cdoc.content),
-                    doc.get_conflicts()))
-            attachments['u1db_conflicts'] = {
-                'follows': True,
-                'content_type': 'application/octet-stream',
-                'length': len(conflicts),
-            }
-            parts.append(conflicts)
-        # store old transactions, if any
-        transactions = old_doc.transactions[:] if old_doc is not None else []
-        # create a new transaction id and timestamp it so the transaction log
-        # is consistent when querying the database.
-        transactions.append(
-            # here we store milliseconds to keep consistent with javascript
-            # Date.prototype.getTime() which was used before inside a couchdb
-            # update handler.
-            (int(time.time() * 1000),
-             self._allocate_transaction_id()))
-        # build the couch document
-        couch_doc = {
-            '_id': doc.doc_id,
-            'u1db_rev': doc.rev,
-            'u1db_transactions': transactions,
-            '_attachments': attachments,
-        }
-        # if we are updating a doc we have to add the couch doc revision
-        if old_doc is not None:
-            couch_doc['_rev'] = old_doc.couch_rev
-        # prepare the multipart PUT
-        buf = StringIO()
-        headers = {}
-        envelope = MultipartWriter(buf, headers=headers, subtype='related')
-        envelope.add('application/json', json.dumps(couch_doc))
-        for part in parts:
-            envelope.add('application/octet-stream', part)
-        envelope.close()
-        # try to save and fail if there's a revision conflict
-        try:
-            resource = self._new_resource()
-            resource.put_json(
-                doc.doc_id, body=str(buf.getvalue()), headers=envelope.headers)
-        except ResourceConflict:
-            raise RevisionConflict()
+        last_transaction =\
+            self._database.save_document(old_doc, doc,
+                                         self._allocate_transaction_id())
         if self.replica_uid + '_gen' in self.cache:
-            gen_info = self.cache[self.replica_uid + '_gen']
-            gen_info['generation'] += 1
-            gen_info['transaction_id'] = transactions[-1][1]
+            gen, trans = self.cache[self.replica_uid + '_gen']
+            gen += 1
+            trans = last_transaction
+            self.cache[self.replica_uid + '_gen'] = (gen, trans)
 
     def put_doc(self, doc):
         """
@@ -711,53 +445,8 @@ class CouchDatabase(CommonBackend):
                  to the last intervening change and sorted by generation (old
                  changes first)
         :rtype: (int, str, [(str, int, str)])
-
-        :raise MissingDesignDocError: Raised when tried to access a missing
-                                      design document.
-        :raise MissingDesignDocListFunctionError: Raised when trying to access
-                                                  a missing list function on a
-                                                  design document.
-        :raise MissingDesignDocNamedViewError: Raised when trying to access a
-                                               missing named view on a design
-                                               document.
-        :raise MissingDesignDocDeletedError: Raised when trying to access a
-                                             deleted design document.
-        :raise MissingDesignDocUnknownError: Raised when failed to access a
-                                             design document for an yet
-                                             unknown reason.
         """
-        # query a couch list function
-        ddoc_path = [
-            '_design', 'transactions', '_list', 'whats_changed', 'log'
-        ]
-        res = self._database.resource(*ddoc_path)
-        try:
-            response = res.get_json(old_gen=old_generation)
-            results = map(
-                lambda row:
-                    (row['generation'], row['doc_id'], row['transaction_id']),
-                response[2]['transactions'])
-            results.reverse()
-            cur_gen = old_generation
-            seen = set()
-            changes = []
-            newest_trans_id = ''
-            for generation, doc_id, trans_id in results:
-                if doc_id not in seen:
-                    changes.append((doc_id, generation, trans_id))
-                    seen.add(doc_id)
-            if changes:
-                cur_gen = changes[0][1]  # max generation
-                newest_trans_id = changes[0][2]
-                changes.reverse()
-            else:
-                cur_gen, newest_trans_id = self._get_generation_info()
-
-            return cur_gen, newest_trans_id, changes
-        except ResourceNotFound as e:
-            raise_missing_design_doc_error(e, ddoc_path)
-        except ServerError as e:
-            raise_server_error(e, ddoc_path)
+        return self._database.whats_changed(old_generation)
 
     def delete_doc(self, doc):
         """
@@ -791,25 +480,6 @@ class CouchDatabase(CommonBackend):
         self._put_doc(old_doc, doc)
         return new_rev
 
-    def _build_conflicts(self, doc_id, attached_conflicts):
-        """
-        Build the conflicted documents list from the conflicts attachment
-        fetched from a couch document.
-
-        :param attached_conflicts: The document's conflicts as fetched from a
-                                   couch document attachment.
-        :type attached_conflicts: dict
-        """
-        conflicts = []
-        for doc_rev, content in attached_conflicts:
-            doc = self._factory(doc_id, doc_rev)
-            if content is None:
-                doc.make_tombstone()
-            else:
-                doc.content = content
-            conflicts.append(doc)
-        return conflicts
-
     def get_doc_conflicts(self, doc_id, couch_rev=None):
         """
         Get the conflicted versions of a document.
@@ -823,22 +493,7 @@ class CouchDatabase(CommonBackend):
         :return: A list of conflicted versions of the document.
         :rtype: list
         """
-        # request conflicts attachment from server
-        params = {}
-        conflicts = []
-        if couch_rev is not None:
-            params['rev'] = couch_rev  # restric document's couch revision
-        else:
-            # TODO: move into resource logic!
-            first_entry = self._get_doc(doc_id, check_for_conflicts=True)
-            conflicts.append(first_entry)
-        resource = self._database.resource(doc_id, 'u1db_conflicts')
-        try:
-            response = resource.get_json(**params)
-            return conflicts + self._build_conflicts(
-                doc_id, json.loads(response[2].read()))
-        except ResourceNotFound:
-            return []
+        return self._database.get_doc_conflicts(doc_id, couch_rev)
 
     def _get_replica_gen_and_trans_id(self, other_replica_uid):
         """
@@ -859,22 +514,7 @@ class CouchDatabase(CommonBackend):
                  synchronized with the replica, this is (0, '').
         :rtype: (int, str)
         """
-        if other_replica_uid in self.cache:
-            return self.cache[other_replica_uid]
-
-        doc_id = 'u1db_sync_%s' % other_replica_uid
-        try:
-            doc = self._database[doc_id]
-        except ResourceNotFound:
-            doc = {
-                '_id': doc_id,
-                'generation': 0,
-                'transaction_id': '',
-            }
-            self._database.save(doc)
-        result = doc['generation'], doc['transaction_id']
-        self.cache[other_replica_uid] = result
-        return result
+        return self._database._get_replica_gen_and_trans_id(other_replica_uid)
 
     def _set_replica_gen_and_trans_id(self, other_replica_uid,
                                       other_generation, other_transaction_id,
@@ -937,14 +577,9 @@ class CouchDatabase(CommonBackend):
         """
         self.cache[other_replica_uid] = (other_generation,
                                          other_transaction_id)
-        doc_id = 'u1db_sync_%s' % other_replica_uid
-        try:
-            doc = self._database[doc_id]
-        except ResourceNotFound:
-            doc = {'_id': doc_id}
-        doc['generation'] = other_generation
-        doc['transaction_id'] = other_transaction_id
-        self._database.save(doc)
+        self._database._do_set_replica_gen_and_trans_id(other_replica_uid,
+                                                        other_generation,
+                                                        other_transaction_id)
 
     def _force_doc_sync_conflict(self, doc):
         """
@@ -1099,25 +734,8 @@ class CouchDatabase(CommonBackend):
                  in matching doc_ids order.
         :rtype: iterable
         """
-        # Workaround for:
-        #
-        #   http://bugs.python.org/issue7980
-        #   https://leap.se/code/issues/5449
-        #
-        # python-couchdb uses time.strptime, which is not thread safe. In
-        # order to avoid the problem described on the issues above, we preload
-        # strptime here by evaluating the conversion of an arbitrary date.
-        # This will not be needed when/if we switch from python-couchdb to
-        # paisley.
-        time.strptime('Mar 8 1917', '%b %d %Y')
-        get_one = lambda doc_id: self._get_doc(doc_id, check_for_conflicts)
-        docs = [THREAD_POOL.apply_async(get_one, [doc_id])
-                for doc_id in doc_ids]
-        for doc in docs:
-            doc = doc.get()
-            if not doc or not include_deleted and doc.is_tombstone():
-                continue
-            yield doc
+        return self._database.get_docs(doc_ids, check_for_conflicts,
+                                       include_deleted)
 
     def _prune_conflicts(self, doc, doc_vcr):
         """
@@ -1147,6 +765,632 @@ class CouchDatabase(CommonBackend):
                 doc.rev = doc_vcr.as_str()
             doc.delete_conflicts(c_revs_to_prune)
 
+
+class CouchDatabase(object):
+    """
+    Holds CouchDB related code.
+    This class gives methods to encapsulate database operations and hide
+    CouchDB details from backend code.
+    """
+
+    @classmethod
+    def open_database(cls, url, create, ensure_ddocs=False):
+        """
+        Open a U1DB database using CouchDB as backend.
+
+        :param url: the url of the database replica
+        :type url: str
+        :param create: should the replica be created if it does not exist?
+        :type create: bool
+        :param replica_uid: an optional unique replica identifier
+        :type replica_uid: str
+        :param ensure_ddocs: Ensure that the design docs exist on server.
+        :type ensure_ddocs: bool
+
+        :return: the database instance
+        :rtype: SoledadBackend
+        """
+        # get database from url
+        m = re.match('(^https?://[^/]+)/(.+)$', url)
+        if not m:
+            raise InvalidURLError
+        url = m.group(1)
+        dbname = m.group(2)
+        with couch_server(url) as server:
+            try:
+                server[dbname]
+            except ResourceNotFound:
+                if not create:
+                    raise DatabaseDoesNotExist()
+                server.create(dbname)
+        return cls(
+            url, dbname, ensure_ddocs=ensure_ddocs)
+
+    def __init__(self, url, dbname, ensure_ddocs=True,
+                 database_security=None):
+        self._session = Session(timeout=COUCH_TIMEOUT)
+        self._url = url
+        self._dbname = dbname
+        self._database = Database(
+            urljoin(url, dbname),
+            self._session)
+        self._database.info()
+        if ensure_ddocs:
+            self.ensure_ddocs_on_db()
+            self.ensure_security_ddoc(database_security)
+
+    def ensure_ddocs_on_db(self):
+        """
+        Ensure that the design documents used by the backend exist on the
+        couch database.
+        """
+        for ddoc_name in ['docs', 'syncs', 'transactions']:
+            try:
+                self._database.resource('_design',
+                                        ddoc_name, '_info').get_json()
+            except ResourceNotFound:
+                ddoc = json.loads(
+                    binascii.a2b_base64(
+                        getattr(ddocs, ddoc_name)))
+                self._database.save(ddoc)
+
+    def ensure_security_ddoc(self, security_config=None):
+        """
+        Make sure that only soledad user is able to access this database as
+        an unprivileged member, meaning that administration access will
+        be forbidden even inside an user database.
+        The goal is to make sure that only the lowest access level is given
+        to the unprivileged CouchDB user set on the server process.
+        This is achieved by creating a _security design document, see:
+        http://docs.couchdb.org/en/latest/api/database/security.html
+
+        :param database_security: security configuration parsed from conf file
+        :type cache: dict
+        """
+        security_config = security_config or {}
+        security = self._database.resource.get_json('_security')[2]
+        security['members'] = {'names': [], 'roles': []}
+        security['members']['names'] = security_config.get('members',
+                                                           ['soledad'])
+        security['members']['roles'] = security_config.get('members_roles', [])
+        security['admins'] = {'names': [], 'roles': []}
+        security['admins']['names'] = security_config.get('admins', [])
+        security['admins']['roles'] = security_config.get('admins_roles', [])
+        self._database.resource.put_json('_security', body=security)
+
+    def delete_database(self):
+        """
+        Delete a U1DB CouchDB database.
+        """
+        with couch_server(self._url) as server:
+            del(server[self._dbname])
+
+    def set_replica_uid(self, replica_uid):
+        """
+        Force the replica uid to be set.
+
+        :param replica_uid: The new replica uid.
+        :type replica_uid: str
+        """
+        try:
+            # set on existent config document
+            doc = self._database['u1db_config']
+            doc['replica_uid'] = replica_uid
+        except ResourceNotFound:
+            # or create the config document
+            doc = {
+                '_id': 'u1db_config',
+                'replica_uid': replica_uid,
+            }
+        self._database.save(doc)
+
+    def get_replica_uid(self):
+        """
+        Get the replica uid.
+
+        :return: The replica uid.
+        :rtype: str
+        """
+        try:
+            # grab replica_uid from server
+            doc = self._database['u1db_config']
+            replica_uid = doc['replica_uid']
+            return replica_uid
+        except ResourceNotFound:
+            # create a unique replica_uid
+            replica_uid = uuid.uuid4().hex
+            self.set_replica_uid(replica_uid)
+            return replica_uid
+
+    def close(self):
+        self._database = None
+
+    def get_all_docs(self, include_deleted=False):
+        """
+        Get the JSON content for all documents in the database.
+
+        :param include_deleted: If set to True, deleted documents will be
+                                returned with empty content. Otherwise deleted
+                                documents will not be included in the results.
+        :type include_deleted: bool
+
+        :return: (generation, [CouchDocument])
+            The current generation of the database, followed by a list of all
+            the documents in the database.
+        :rtype: (int, [CouchDocument])
+        """
+
+        generation, _ = self._get_generation_info()
+        results = list(self.get_docs(self._database,
+                                     include_deleted=include_deleted))
+        return (generation, results)
+
+    def get_docs(self, doc_ids, check_for_conflicts=True,
+                 include_deleted=False):
+        """
+        Get the JSON content for many documents.
+
+        :param doc_ids: A list of document identifiers or None for all.
+        :type doc_ids: list
+        :param check_for_conflicts: If set to False, then the conflict check
+                                    will be skipped, and 'None' will be
+                                    returned instead of True/False.
+        :type check_for_conflicts: bool
+        :param include_deleted: If set to True, deleted documents will be
+                                returned with empty content. Otherwise deleted
+                                documents will not be included in the results.
+        :return: iterable giving the Document object for each document id
+                 in matching doc_ids order.
+        :rtype: iterable
+        """
+        # Workaround for:
+        #
+        #   http://bugs.python.org/issue7980
+        #   https://leap.se/code/issues/5449
+        #
+        # python-couchdb uses time.strptime, which is not thread safe. In
+        # order to avoid the problem described on the issues above, we preload
+        # strptime here by evaluating the conversion of an arbitrary date.
+        # This will not be needed when/if we switch from python-couchdb to
+        # paisley.
+        time.strptime('Mar 8 1917', '%b %d %Y')
+        get_one = lambda doc_id: self._get_doc(doc_id, check_for_conflicts)
+        docs = [THREAD_POOL.apply_async(get_one, [doc_id])
+                for doc_id in doc_ids]
+        for doc in docs:
+            doc = doc.get()
+            if not doc or not include_deleted and doc.is_tombstone():
+                continue
+            yield doc
+
+    def _get_doc(self, doc_id, check_for_conflicts=False):
+        """
+        Extract the document from storage.
+
+        This can return None if the document doesn't exist.
+
+        :param doc_id: The unique document identifier
+        :type doc_id: str
+        :param check_for_conflicts: If set to False, then the conflict check
+                                    will be skipped.
+        :type check_for_conflicts: bool
+
+        :return: The document.
+        :rtype: CouchDocument
+        """
+        # get document with all attachments (u1db content and eventual
+        # conflicts)
+        try:
+            result = \
+                self._database.resource(doc_id).get_json(
+                    attachments=True)[2]
+        except ResourceNotFound:
+            return None
+        return self.__parse_doc_from_couch(result, doc_id, check_for_conflicts)
+
+    def __parse_doc_from_couch(self, result, doc_id,
+                               check_for_conflicts=False):
+        # restrict to u1db documents
+        if 'u1db_rev' not in result:
+            return None
+        doc = CouchDocument(doc_id, result['u1db_rev'])
+        # set contents or make tombstone
+        if '_attachments' not in result \
+                or 'u1db_content' not in result['_attachments']:
+            doc.make_tombstone()
+        else:
+            doc.content = json.loads(
+                binascii.a2b_base64(
+                    result['_attachments']['u1db_content']['data']))
+        # determine if there are conflicts
+        if check_for_conflicts \
+                and '_attachments' in result \
+                and 'u1db_conflicts' in result['_attachments']:
+            doc.set_conflicts(
+                self._build_conflicts(
+                    doc.doc_id,
+                    json.loads(binascii.a2b_base64(
+                        result['_attachments']['u1db_conflicts']['data']))))
+        # store couch revision
+        doc.couch_rev = result['_rev']
+        # store transactions
+        doc.transactions = result['u1db_transactions']
+        return doc
+
+    def _build_conflicts(self, doc_id, attached_conflicts):
+        """
+        Build the conflicted documents list from the conflicts attachment
+        fetched from a couch document.
+
+        :param attached_conflicts: The document's conflicts as fetched from a
+                                   couch document attachment.
+        :type attached_conflicts: dict
+        """
+        conflicts = []
+        for doc_rev, content in attached_conflicts:
+            doc = CouchDocument(doc_id, doc_rev)
+            if content is None:
+                doc.make_tombstone()
+            else:
+                doc.content = content
+            conflicts.append(doc)
+        return conflicts
+
+    def _get_trans_id_for_gen(self, generation):
+        """
+        Get the transaction id corresponding to a particular generation.
+
+        :param generation: The generation for which to get the transaction id.
+        :type generation: int
+
+        :return: The transaction id for C{generation}.
+        :rtype: str
+
+        :raise InvalidGeneration: Raised when the generation does not exist.
+        :raise MissingDesignDocError: Raised when tried to access a missing
+                                      design document.
+        :raise MissingDesignDocListFunctionError: Raised when trying to access
+                                                  a missing list function on a
+                                                  design document.
+        :raise MissingDesignDocNamedViewError: Raised when trying to access a
+                                               missing named view on a design
+                                               document.
+        :raise MissingDesignDocDeletedError: Raised when trying to access a
+                                             deleted design document.
+        :raise MissingDesignDocUnknownError: Raised when failed to access a
+                                             design document for an yet
+                                             unknown reason.
+        """
+        if generation == 0:
+            return ''
+        # query a couch list function
+        ddoc_path = [
+            '_design', 'transactions', '_list', 'trans_id_for_gen', 'log'
+        ]
+        res = self._database.resource(*ddoc_path)
+        try:
+            response = res.get_json(gen=generation)
+            if response[2] == {}:
+                raise InvalidGeneration
+            return response[2]['transaction_id']
+        except ResourceNotFound as e:
+            raise_missing_design_doc_error(e, ddoc_path)
+        except ServerError as e:
+            raise_server_error(e, ddoc_path)
+
+    def _get_replica_gen_and_trans_id(self, other_replica_uid):
+        """
+        Return the last known generation and transaction id for the other db
+        replica.
+
+        When you do a synchronization with another replica, the Database keeps
+        track of what generation the other database replica was at, and what
+        the associated transaction id was.  This is used to determine what data
+        needs to be sent, and if two databases are claiming to be the same
+        replica.
+
+        :param other_replica_uid: The identifier for the other replica.
+        :type other_replica_uid: str
+
+        :return: A tuple containing the generation and transaction id we
+                 encountered during synchronization. If we've never
+                 synchronized with the replica, this is (0, '').
+        :rtype: (int, str)
+        """
+        doc_id = 'u1db_sync_%s' % other_replica_uid
+        try:
+            doc = self._database[doc_id]
+        except ResourceNotFound:
+            doc = {
+                '_id': doc_id,
+                'generation': 0,
+                'transaction_id': '',
+            }
+            self._database.save(doc)
+        result = doc['generation'], doc['transaction_id']
+        return result
+
+    def get_doc_conflicts(self, doc_id, couch_rev=None):
+        """
+        Get the conflicted versions of a document.
+
+        If the C{couch_rev} parameter is not None, conflicts for a specific
+        document's couch revision are returned.
+
+        :param couch_rev: The couch document revision.
+        :type couch_rev: str
+
+        :return: A list of conflicted versions of the document.
+        :rtype: list
+        """
+        # request conflicts attachment from server
+        params = {}
+        conflicts = []
+        if couch_rev is not None:
+            params['rev'] = couch_rev  # restric document's couch revision
+        else:
+            # TODO: move into resource logic!
+            first_entry = self._get_doc(doc_id, check_for_conflicts=True)
+            conflicts.append(first_entry)
+        resource = self._database.resource(doc_id, 'u1db_conflicts')
+        try:
+            response = resource.get_json(**params)
+            return conflicts + self._build_conflicts(
+                doc_id, json.loads(response[2].read()))
+        except ResourceNotFound:
+            return []
+
+    def _do_set_replica_gen_and_trans_id(
+            self, other_replica_uid, other_generation, other_transaction_id,
+            number_of_docs=None, doc_idx=None, sync_id=None):
+        """
+        Set the last-known generation and transaction id for the other
+        database replica.
+
+        We have just performed some synchronization, and we want to track what
+        generation the other replica was at. See also
+        _get_replica_gen_and_trans_id.
+
+        :param other_replica_uid: The U1DB identifier for the other replica.
+        :type other_replica_uid: str
+        :param other_generation: The generation number for the other replica.
+        :type other_generation: int
+        :param other_transaction_id: The transaction id associated with the
+                                     generation.
+        :type other_transaction_id: str
+        :param number_of_docs: The total amount of documents sent on this sync
+                               session.
+        :type number_of_docs: int
+        :param doc_idx: The index of the current document being sent.
+        :type doc_idx: int
+        :param sync_id: The id of the current sync session.
+        :type sync_id: str
+        """
+        doc_id = 'u1db_sync_%s' % other_replica_uid
+        try:
+            doc = self._database[doc_id]
+        except ResourceNotFound:
+            doc = {'_id': doc_id}
+        doc['generation'] = other_generation
+        doc['transaction_id'] = other_transaction_id
+        self._database.save(doc)
+
+    def _get_transaction_log(self):
+        """
+        This is only for the test suite, it is not part of the api.
+
+        :return: The complete transaction log.
+        :rtype: [(str, str)]
+
+        :raise MissingDesignDocError: Raised when tried to access a missing
+                                      design document.
+        :raise MissingDesignDocListFunctionError: Raised when trying to access
+                                                  a missing list function on a
+                                                  design document.
+        :raise MissingDesignDocNamedViewError: Raised when trying to access a
+                                               missing named view on a design
+                                               document.
+        :raise MissingDesignDocDeletedError: Raised when trying to access a
+                                             deleted design document.
+        :raise MissingDesignDocUnknownError: Raised when failed to access a
+                                             design document for an yet
+                                             unknown reason.
+        """
+        # query a couch view
+        ddoc_path = ['_design', 'transactions', '_view', 'log']
+        res = self._database.resource(*ddoc_path)
+        try:
+            response = res.get_json()
+            return map(
+                lambda row: (row['id'], row['value']),
+                response[2]['rows'])
+        except ResourceNotFound as e:
+            raise_missing_design_doc_error(e, ddoc_path)
+
+    def whats_changed(self, old_generation=0):
+        """
+        Return a list of documents that have changed since old_generation.
+
+        :param old_generation: The generation of the database in the old
+                               state.
+        :type old_generation: int
+
+        :return: (generation, trans_id, [(doc_id, generation, trans_id),...])
+                 The current generation of the database, its associated
+                 transaction id, and a list of of changed documents since
+                 old_generation, represented by tuples with for each document
+                 its doc_id and the generation and transaction id corresponding
+                 to the last intervening change and sorted by generation (old
+                 changes first)
+        :rtype: (int, str, [(str, int, str)])
+
+        :raise MissingDesignDocError: Raised when tried to access a missing
+                                      design document.
+        :raise MissingDesignDocListFunctionError: Raised when trying to access
+                                                  a missing list function on a
+                                                  design document.
+        :raise MissingDesignDocNamedViewError: Raised when trying to access a
+                                               missing named view on a design
+                                               document.
+        :raise MissingDesignDocDeletedError: Raised when trying to access a
+                                             deleted design document.
+        :raise MissingDesignDocUnknownError: Raised when failed to access a
+                                             design document for an yet
+                                             unknown reason.
+        """
+        # query a couch list function
+        ddoc_path = [
+            '_design', 'transactions', '_list', 'whats_changed', 'log'
+        ]
+        res = self._database.resource(*ddoc_path)
+        try:
+            response = res.get_json(old_gen=old_generation)
+            results = map(
+                lambda row:
+                    (row['generation'], row['doc_id'], row['transaction_id']),
+                response[2]['transactions'])
+            results.reverse()
+            cur_gen = old_generation
+            seen = set()
+            changes = []
+            newest_trans_id = ''
+            for generation, doc_id, trans_id in results:
+                if doc_id not in seen:
+                    changes.append((doc_id, generation, trans_id))
+                    seen.add(doc_id)
+            if changes:
+                cur_gen = changes[0][1]  # max generation
+                newest_trans_id = changes[0][2]
+                changes.reverse()
+            else:
+                cur_gen, newest_trans_id = self._get_generation_info()
+
+            return cur_gen, newest_trans_id, changes
+        except ResourceNotFound as e:
+            raise_missing_design_doc_error(e, ddoc_path)
+        except ServerError as e:
+            raise_server_error(e, ddoc_path)
+
+    def _get_generation_info(self):
+        """
+        Return the current generation.
+
+        :return: A tuple containing the current generation and transaction id.
+        :rtype: (int, str)
+
+        :raise MissingDesignDocError: Raised when tried to access a missing
+                                      design document.
+        :raise MissingDesignDocListFunctionError: Raised when trying to access
+                                                  a missing list function on a
+                                                  design document.
+        :raise MissingDesignDocNamedViewError: Raised when trying to access a
+                                               missing named view on a design
+                                               document.
+        :raise MissingDesignDocDeletedError: Raised when trying to access a
+                                             deleted design document.
+        :raise MissingDesignDocUnknownError: Raised when failed to access a
+                                             design document for an yet
+                                             unknown reason.
+        """
+        # query a couch list function
+        ddoc_path = ['_design', 'transactions', '_list', 'generation', 'log']
+        res = self._database.resource(*ddoc_path)
+        try:
+            response = res.get_json()
+            return (response[2]['generation'], response[2]['transaction_id'])
+        except ResourceNotFound as e:
+            raise_missing_design_doc_error(e, ddoc_path)
+        except ServerError as e:
+            raise_server_error(e, ddoc_path)
+
+    def save_document(self, old_doc, doc, transaction_id):
+        """
+        Put the document in the Couch backend database.
+
+        Note that C{old_doc} must have been fetched with the parameter
+        C{check_for_conflicts} equal to True, so we can properly update the
+        new document using the conflict information from the old one.
+
+        :param old_doc: The old document version.
+        :type old_doc: CouchDocument
+        :param doc: The document to be put.
+        :type doc: CouchDocument
+
+        :raise RevisionConflict: Raised when trying to update a document but
+                                 couch revisions mismatch.
+        :raise MissingDesignDocError: Raised when tried to access a missing
+                                      design document.
+        :raise MissingDesignDocListFunctionError: Raised when trying to access
+                                                  a missing list function on a
+                                                  design document.
+        :raise MissingDesignDocNamedViewError: Raised when trying to access a
+                                               missing named view on a design
+                                               document.
+        :raise MissingDesignDocDeletedError: Raised when trying to access a
+                                             deleted design document.
+        :raise MissingDesignDocUnknownError: Raised when failed to access a
+                                             design document for an yet
+                                             unknown reason.
+        """
+        attachments = {}  # we save content and conflicts as attachments
+        parts = []  # and we put it using couch's multipart PUT
+        # save content as attachment
+        if doc.is_tombstone() is False:
+            content = doc.get_json()
+            attachments['u1db_content'] = {
+                'follows': True,
+                'content_type': 'application/octet-stream',
+                'length': len(content),
+            }
+            parts.append(content)
+        # save conflicts as attachment
+        if doc.has_conflicts is True:
+            conflicts = json.dumps(
+                map(lambda cdoc: (cdoc.rev, cdoc.content),
+                    doc.get_conflicts()))
+            attachments['u1db_conflicts'] = {
+                'follows': True,
+                'content_type': 'application/octet-stream',
+                'length': len(conflicts),
+            }
+            parts.append(conflicts)
+        # store old transactions, if any
+        transactions = old_doc.transactions[:] if old_doc is not None else []
+        # create a new transaction id and timestamp it so the transaction log
+        # is consistent when querying the database.
+        transactions.append(
+            # here we store milliseconds to keep consistent with javascript
+            # Date.prototype.getTime() which was used before inside a couchdb
+            # update handler.
+            (int(time.time() * 1000),
+             transaction_id))
+        # build the couch document
+        couch_doc = {
+            '_id': doc.doc_id,
+            'u1db_rev': doc.rev,
+            'u1db_transactions': transactions,
+            '_attachments': attachments,
+        }
+        # if we are updating a doc we have to add the couch doc revision
+        if old_doc is not None:
+            couch_doc['_rev'] = old_doc.couch_rev
+        # prepare the multipart PUT
+        buf = StringIO()
+        headers = {}
+        envelope = MultipartWriter(buf, headers=headers, subtype='related')
+        envelope.add('application/json', json.dumps(couch_doc))
+        for part in parts:
+            envelope.add('application/octet-stream', part)
+        envelope.close()
+        # try to save and fail if there's a revision conflict
+        try:
+            resource = self._new_resource()
+            resource.put_json(
+                doc.doc_id, body=str(buf.getvalue()), headers=headers)
+        except ResourceConflict:
+            raise RevisionConflict()
+        return transactions[-1][1]
+
     def _new_resource(self, *path):
         """
         Return a new resource for accessing a couch database.
@@ -1165,7 +1409,7 @@ class CouchDatabase(CommonBackend):
 class CouchSyncTarget(CommonSyncTarget):
 
     """
-    Functionality for using a CouchDatabase as a synchronization target.
+    Functionality for using a SoledadBackend as a synchronization target.
     """
 
     def get_sync_info(self, source_replica_uid):
@@ -1222,13 +1466,12 @@ class CouchServerState(ServerState):
         :param dbname: The name of the database to open.
         :type dbname: str
 
-        :return: The CouchDatabase object.
-        :rtype: CouchDatabase
+        :return: The SoledadBackend object.
+        :rtype: SoledadBackend
         """
-        db = CouchDatabase(
-            self.couch_url,
-            dbname,
-            ensure_ddocs=False)
+        url = urljoin(self.couch_url, dbname)
+        db = SoledadBackend.open_database(url, create=False,
+                                          ensure_ddocs=False)
         return db
 
     def ensure_database(self, dbname):
@@ -1240,8 +1483,8 @@ class CouchServerState(ServerState):
 
         :raise Unauthorized: If disabled or other error was raised.
 
-        :return: The CouchDatabase object and its replica_uid.
-        :rtype: (CouchDatabase, str)
+        :return: The SoledadBackend object and its replica_uid.
+        :rtype: (SoledadBackend, str)
         """
         if not self.create_cmd:
             raise Unauthorized()
diff --git a/common/src/leap/soledad/common/errors.py b/common/src/leap/soledad/common/errors.py
index 2ba05839..ea9d6ce4 100644
--- a/common/src/leap/soledad/common/errors.py
+++ b/common/src/leap/soledad/common/errors.py
@@ -132,7 +132,7 @@ class CouldNotObtainLockError(SoledadError):
 
 
 #
-# CouchDatabase errors
+# SoledadBackend errors
 #
 
 @register_exception
diff --git a/common/src/leap/soledad/common/tests/test_couch.py b/common/src/leap/soledad/common/tests/test_couch.py
index 86cc0881..b3536a6a 100644
--- a/common/src/leap/soledad/common/tests/test_couch.py
+++ b/common/src/leap/soledad/common/tests/test_couch.py
@@ -56,7 +56,7 @@ from u1db.backends.inmemory import InMemoryIndex
 class TestCouchBackendImpl(CouchDBTestCase):
 
     def test__allocate_doc_id(self):
-        db = couch.CouchDatabase.open_database(
+        db = couch.SoledadBackend.open_database(
             urljoin(
                 'http://localhost:' + str(self.couch_port),
                 ('test-%s' % uuid4().hex)
@@ -78,7 +78,7 @@ class TestCouchBackendImpl(CouchDBTestCase):
 def make_couch_database_for_test(test, replica_uid):
     port = str(test.couch_port)
     dbname = ('test-%s' % uuid4().hex)
-    db = couch.CouchDatabase.open_database(
+    db = couch.SoledadBackend.open_database(
         urljoin('http://localhost:' + port, dbname),
         create=True,
         replica_uid=replica_uid or 'test',
@@ -91,7 +91,7 @@ def copy_couch_database_for_test(test, db):
     port = str(test.couch_port)
     couch_url = 'http://localhost:' + port
     new_dbname = db._dbname + '_copy'
-    new_db = couch.CouchDatabase.open_database(
+    new_db = couch.SoledadBackend.open_database(
         urljoin(couch_url, new_dbname),
         create=True,
         replica_uid=db._replica_uid or 'test')
@@ -150,7 +150,7 @@ class CouchTests(
     scenarios = COUCH_SCENARIOS
 
 
-class CouchDatabaseTests(
+class SoledadBackendTests(
         TestWithScenarios,
         test_backends.LocalDatabaseTests,
         CouchDBTestCase):
@@ -206,7 +206,7 @@ simple_doc = tests.simple_doc
 nested_doc = tests.nested_doc
 
 
-class CouchDatabaseSyncTargetTests(
+class SoledadBackendSyncTargetTests(
         TestWithScenarios,
         DatabaseBaseTests,
         CouchDBTestCase):
@@ -532,13 +532,10 @@ class CouchDatabaseSyncTargetTests(
 
 # The following tests need that the database have an index, so we fake one.
 
-class IndexedCouchDatabase(couch.CouchDatabase):
+class IndexedSoledadBackend(couch.SoledadBackend):
 
-    def __init__(self, url, dbname, replica_uid=None, ensure_ddocs=True,
-                 database_security=None):
-        old_class.__init__(self, url, dbname, replica_uid=replica_uid,
-                           ensure_ddocs=ensure_ddocs,
-                           database_security=database_security)
+    def __init__(self, db, replica_uid=None):
+        old_class.__init__(self, db, replica_uid=replica_uid)
         self._indexes = {}
 
     def _put_doc(self, old_doc, doc):
@@ -608,11 +605,11 @@ class IndexedCouchDatabase(couch.CouchDatabase):
         return list(set([tuple(key.split('\x01')) for key in keys]))
 
 
-# monkey patch CouchDatabase (once) to include virtual indexes
-if getattr(couch.CouchDatabase, '_old_class', None) is None:
-    old_class = couch.CouchDatabase
-    IndexedCouchDatabase._old_class = old_class
-    couch.CouchDatabase = IndexedCouchDatabase
+# monkey patch SoledadBackend (once) to include virtual indexes
+if getattr(couch.SoledadBackend, '_old_class', None) is None:
+    old_class = couch.SoledadBackend
+    IndexedSoledadBackend._old_class = old_class
+    couch.SoledadBackend = IndexedSoledadBackend
 
 
 sync_scenarios = []
@@ -623,7 +620,7 @@ for name, scenario in COUCH_SCENARIOS:
     scenario = dict(scenario)
 
 
-class CouchDatabaseSyncTests(
+class SoledadBackendSyncTests(
         TestWithScenarios,
         DatabaseBaseTests,
         CouchDBTestCase):
@@ -1319,7 +1316,7 @@ class CouchDatabaseSyncTests(
         self.assertEqual(cont2, self.db1.get_doc("2").get_json())
 
 
-class CouchDatabaseExceptionsTests(CouchDBTestCase):
+class SoledadBackendExceptionsTests(CouchDBTestCase):
 
     def setUp(self):
         CouchDBTestCase.setUp(self)
@@ -1343,10 +1340,6 @@ class CouchDatabaseExceptionsTests(CouchDBTestCase):
         design docs are not present.
         """
         self.create_db(ensure=False)
-        # _get_generation()
-        self.assertRaises(
-            errors.MissingDesignDocError,
-            self.db._get_generation)
         # _get_generation_info()
         self.assertRaises(
             errors.MissingDesignDocError,
@@ -1374,10 +1367,6 @@ class CouchDatabaseExceptionsTests(CouchDBTestCase):
         transactions = self.db._database['_design/transactions']
         transactions['lists'] = {}
         self.db._database.save(transactions)
-        # _get_generation()
-        self.assertRaises(
-            errors.MissingDesignDocListFunctionError,
-            self.db._get_generation)
         # _get_generation_info()
         self.assertRaises(
             errors.MissingDesignDocListFunctionError,
@@ -1401,10 +1390,6 @@ class CouchDatabaseExceptionsTests(CouchDBTestCase):
         transactions = self.db._database['_design/transactions']
         del transactions['lists']
         self.db._database.save(transactions)
-        # _get_generation()
-        self.assertRaises(
-            errors.MissingDesignDocListFunctionError,
-            self.db._get_generation)
         # _get_generation_info()
         self.assertRaises(
             errors.MissingDesignDocListFunctionError,
@@ -1436,10 +1421,6 @@ class CouchDatabaseExceptionsTests(CouchDBTestCase):
         transactions = self.db._database['_design/transactions']
         del transactions['views']
         self.db._database.save(transactions)
-        # _get_generation()
-        self.assertRaises(
-            errors.MissingDesignDocNamedViewError,
-            self.db._get_generation)
         # _get_generation_info()
         self.assertRaises(
             errors.MissingDesignDocNamedViewError,
@@ -1469,10 +1450,6 @@ class CouchDatabaseExceptionsTests(CouchDBTestCase):
         del self.db._database['_design/syncs']
         # delete _design/transactions
         del self.db._database['_design/transactions']
-        # _get_generation()
-        self.assertRaises(
-            errors.MissingDesignDocDeletedError,
-            self.db._get_generation)
         # _get_generation_info()
         self.assertRaises(
             errors.MissingDesignDocDeletedError,
diff --git a/common/src/leap/soledad/common/tests/test_couch_operations_atomicity.py b/common/src/leap/soledad/common/tests/test_couch_operations_atomicity.py
index 507f2984..2c2daf05 100644
--- a/common/src/leap/soledad/common/tests/test_couch_operations_atomicity.py
+++ b/common/src/leap/soledad/common/tests/test_couch_operations_atomicity.py
@@ -26,7 +26,7 @@ from twisted.internet import defer
 from uuid import uuid4
 
 from leap.soledad.client import Soledad
-from leap.soledad.common.couch import CouchDatabase, CouchServerState
+from leap.soledad.common.couch import SoledadBackend, CouchServerState
 
 from leap.soledad.common.tests.util import (
     make_token_soledad_app,
@@ -86,7 +86,7 @@ class CouchAtomicityTestCase(CouchDBTestCase, TestCaseWithServer):
         TestCaseWithServer.setUp(self)
         CouchDBTestCase.setUp(self)
         self.user = ('user-%s' % uuid4().hex)
-        self.db = CouchDatabase.open_database(
+        self.db = SoledadBackend.open_database(
             urljoin(self.couch_url, 'user-' + self.user),
             create=True,
             replica_uid='replica',
diff --git a/common/src/leap/soledad/common/tests/test_server.py b/common/src/leap/soledad/common/tests/test_server.py
index 7c006121..5810ce31 100644
--- a/common/src/leap/soledad/common/tests/test_server.py
+++ b/common/src/leap/soledad/common/tests/test_server.py
@@ -31,7 +31,7 @@ from twisted.trial import unittest
 
 from leap.soledad.common.couch import (
     CouchServerState,
-    CouchDatabase,
+    SoledadBackend,
 )
 from leap.soledad.common.tests.u1db_tests import TestCaseWithServer
 from leap.soledad.common.tests.test_couch import CouchDBTestCase
@@ -358,7 +358,7 @@ class EncryptedSyncTestCase(
             passphrase=passphrase)
 
         # ensure remote db exists before syncing
-        db = CouchDatabase.open_database(
+        db = SoledadBackend.open_database(
             urljoin(self.couch_url, 'user-' + user),
             create=True,
             ensure_ddocs=True)
@@ -488,7 +488,7 @@ class LockResourceTestCase(
         self.tempdir = tempfile.mkdtemp(prefix="leap_tests-")
         TestCaseWithServer.setUp(self)
         # create the databases
-        db = CouchDatabase.open_database(
+        db = SoledadBackend.open_database(
             urljoin(self.couch_url, ('shared-%s' % (uuid4().hex))),
             create=True,
             ensure_ddocs=True)
diff --git a/common/src/leap/soledad/common/tests/test_sync.py b/common/src/leap/soledad/common/tests/test_sync.py
index 1041367b..88443179 100644
--- a/common/src/leap/soledad/common/tests/test_sync.py
+++ b/common/src/leap/soledad/common/tests/test_sync.py
@@ -101,7 +101,7 @@ class InterruptableSyncTestCase(
             user='user-uuid', server_url=self.getURL())
 
         # ensure remote db exists before syncing
-        db = couch.CouchDatabase.open_database(
+        db = couch.SoledadBackend.open_database(
             urljoin(self.couch_url, 'user-user-uuid'),
             create=True,
             ensure_ddocs=True)
diff --git a/common/src/leap/soledad/common/tests/test_sync_mutex.py b/common/src/leap/soledad/common/tests/test_sync_mutex.py
index 2e2123a7..35cecb8f 100644
--- a/common/src/leap/soledad/common/tests/test_sync_mutex.py
+++ b/common/src/leap/soledad/common/tests/test_sync_mutex.py
@@ -102,7 +102,7 @@ class TestSyncMutex(
         self.startServer()
 
         # ensure remote db exists before syncing
-        db = couch.CouchDatabase.open_database(
+        db = couch.SoledadBackend.open_database(
             urljoin(self.couch_url, 'user-' + self.user),
             create=True,
             ensure_ddocs=True)
diff --git a/common/src/leap/soledad/common/tests/test_sync_target.py b/common/src/leap/soledad/common/tests/test_sync_target.py
index c0987e90..0cf31c3f 100644
--- a/common/src/leap/soledad/common/tests/test_sync_target.py
+++ b/common/src/leap/soledad/common/tests/test_sync_target.py
@@ -265,9 +265,9 @@ class TestSoledadSyncTarget(
                                      replica_trans_id=replica_trans_id,
                                      number_of_docs=number_of_docs,
                                      doc_idx=doc_idx, sync_id=sync_id)
-        from leap.soledad.common.tests.test_couch import IndexedCouchDatabase
+        from leap.soledad.common.tests.test_couch import IndexedSoledadBackend
         self.patch(
-            IndexedCouchDatabase, '_put_doc_if_newer', bomb_put_doc_if_newer)
+            IndexedSoledadBackend, '_put_doc_if_newer', bomb_put_doc_if_newer)
         remote_target = self.getSyncTarget(
             source_replica_uid='replica')
         other_changes = []
diff --git a/common/src/leap/soledad/common/tests/util.py b/common/src/leap/soledad/common/tests/util.py
index 1c7adb91..bfd06856 100644
--- a/common/src/leap/soledad/common/tests/util.py
+++ b/common/src/leap/soledad/common/tests/util.py
@@ -47,7 +47,7 @@ from leap.common.testing.basetest import BaseLeapTest
 
 from leap.soledad.common import soledad_assert
 from leap.soledad.common.document import SoledadDocument
-from leap.soledad.common.couch import CouchDatabase, CouchServerState
+from leap.soledad.common.couch import SoledadBackend, CouchServerState
 from leap.soledad.common.crypto import ENC_SCHEME_KEY
 
 from leap.soledad.client import Soledad
@@ -379,7 +379,7 @@ class CouchServerStateForTests(CouchServerState):
         Create db and append to a list, allowing test to close it later
         """
         dbname = dbname or ('test-%s' % uuid4().hex)
-        db = CouchDatabase.open_database(
+        db = SoledadBackend.open_database(
             urljoin(self.couch_url, dbname),
             True,
             replica_uid=replica_uid or 'test',
diff --git a/server/pkg/create-user-db b/server/pkg/create-user-db
index ae5d15dc..a8ba3833 100755
--- a/server/pkg/create-user-db
+++ b/server/pkg/create-user-db
@@ -19,7 +19,7 @@ import os
 import sys
 import netrc
 import argparse
-from leap.soledad.common.couch import CouchDatabase
+from leap.soledad.common.couch import SoledadBackend
 from leap.soledad.common.couch import is_db_name_valid
 from leap.soledad.common.couch import list_users_dbs
 from leap.soledad.server import load_configuration
@@ -69,7 +69,7 @@ def ensure_database(dbname):
         sys.exit(1)
     url = url_for_db(dbname)
     db_security = CONF['database-security']
-    db = CouchDatabase.open_database(url=url, create=True,
+    db = SoledadBackend.open_database(url=url, create=True,
                                      replica_uid=None, ensure_ddocs=True,
                                      database_security=db_security)
     print ('success! Ensured that database %s exists, with replica_uid: %s' %
diff --git a/server/src/leap/soledad/server/sync.py b/server/src/leap/soledad/server/sync.py
index 92b29102..db25c406 100644
--- a/server/src/leap/soledad/server/sync.py
+++ b/server/src/leap/soledad/server/sync.py
@@ -32,7 +32,7 @@ class SyncExchange(sync.SyncExchange):
     def __init__(self, db, source_replica_uid, last_known_generation, sync_id):
         """
         :param db: The target syncing database.
-        :type db: CouchDatabase
+        :type db: SoledadBackend
         :param source_replica_uid: The uid of the source syncing replica.
         :type source_replica_uid: str
         :param last_known_generation: The last target replica generation the