serialized isolation level decorator for postgres transactions

morango/__init__.py

@@ -3,4 +3,4 @@
 from __future__ import unicode_literals
 
 default_app_config = "morango.apps.MorangoConfig"
-__version__ = "0.4.9"
+__version__ = "0.4.11"

morango/sync/operations.py

@@ -6,6 +6,8 @@
 from django.core import exceptions
 from django.core.serializers.json import DjangoJSONEncoder
 from django.db import connection
+from django.db import connections
+from django.db import router
 from django.db import transaction
 from django.db.models import Q
 from django.db.models import signals
@@ -29,6 +31,13 @@
 
 DBBackend = load_backend(connection).SQLWrapper()
 
+# if postgres, get serializable db connection
+db_name = router.db_for_write(Store)
+USING_DB = db_name
+if "postgresql" in transaction.get_connection(USING_DB).vendor:
+    USING_DB = db_name + '-serializable'
+    assert USING_DB in connections, "Please add a `default-serializable` database connection in your django settings file, \
+                                     which copies all the configuration settings of the `default` db connection"
 
 def _join_with_logical_operator(lst, operator):
     op = ") {operator} (".format(operator=operator)
@@ -70,7 +79,7 @@ def _serialize_into_store(profile, filter=None):
     # ensure that we write and retrieve the counter in one go for consistency
     current_id = InstanceIDModel.get_current_instance_and_increment_counter()
 
-    with transaction.atomic():
+    with transaction.atomic(using=USING_DB):
         # create Q objects for filtering by prefixes
         prefix_condition = None
         if filter:
@@ -227,7 +236,7 @@ def _deserialize_from_store(profile):
 
     logger.info("Deserializing records")
     fk_cache = {}
-    with transaction.atomic():
+    with transaction.atomic(using=USING_DB):
         excluded_list = []
         # iterate through classes which are in foreign key dependency order
         for model in syncable_models.get_models(profile):
@@ -316,7 +325,7 @@ def _deserialize_from_store(profile):
     logger.info("Deserialization complete")
 
 
-@transaction.atomic()
+@transaction.atomic(using=USING_DB)
 def _queue_into_buffer(transfersession):
     """
     Takes a chunk of data from the store to be put into the buffer to be sent to another morango instance.
@@ -399,7 +408,7 @@ def _queue_into_buffer(transfersession):
     logger.info("Queuing complete")
 
 
-@transaction.atomic()
+@transaction.atomic(using=USING_DB)
 def _dequeue_into_store(transfersession):
     """
     Takes data from the buffers and merges into the store and record max counters.

tests/testapp/testapp/postgres_test.py

@@ -1,7 +1,16 @@
 """
 A settings module for running tests using a postgres db backend.
 """
-from __future__ import absolute_import, print_function, unicode_literals
+from __future__ import absolute_import
+from __future__ import print_function
+from __future__ import unicode_literals
+
+try:
+    isolation_level = None
+    import psycopg2
+    isolation_level = psycopg2.extensions.ISOLATION_LEVEL_SERIALIZABLE
+except ImportError:
+    pass
 
 from .settings import *  # noqa
 
@@ -15,4 +24,16 @@
             'NAME': 'travis_ci_default'
         }
     },
+    'default-serializable': {
+        'ENGINE': 'django.db.backends.postgresql',
+        'USER': 'postgres',
+        'PASSWORD': '',
+        'NAME': 'default',  # This module should never be used outside of tests -- so this name is irrelevant
+        'TEST': {
+            'NAME': 'travis_ci_default'
+        },
+        'OPTIONS': {
+            'isolation_level': isolation_level,
+        }
+    }
 }