Try once if AutoReconnect is raised

bigchaindb/backend/mongodb/connection.py

@@ -72,12 +72,17 @@ class MongoDBConnection(Connection):
         return self.query()[self.dbname][name]
 
     def run(self, query):
+        try:
             try:
                 return query.run(self.conn)
-        except pymongo.errors.DuplicateKeyError as exc:
+            except pymongo.errors.AutoReconnect as exc:
-            raise DuplicateKeyError from exc
+                logger.warning('Lost connection to the database, '
+                               'retrying query.')
+                return query.run(self.conn)
         except pymongo.errors.AutoReconnect as exc:
             raise ConnectionError from exc
+        except pymongo.errors.DuplicateKeyError as exc:
+            raise DuplicateKeyError from exc
         except pymongo.errors.OperationFailure as exc:
             raise OperationError from exc
 

tests/backend/mongodb/test_connection.py

@@ -79,19 +79,24 @@ def test_connection_run_errors(mock_client, mock_init_repl_set):
                                                ConnectionError)
 
     conn = connect()
-    query = mock.Mock()
 
+    query = mock.Mock()
     query.run.side_effect = pymongo.errors.AutoReconnect('foo')
     with pytest.raises(ConnectionError):
         conn.run(query)
+    assert query.run.call_count == 2
 
+    query = mock.Mock()
     query.run.side_effect = pymongo.errors.DuplicateKeyError('foo')
     with pytest.raises(DuplicateKeyError):
         conn.run(query)
+    assert query.run.call_count == 1
 
+    query = mock.Mock()
     query.run.side_effect = pymongo.errors.OperationFailure('foo')
     with pytest.raises(OperationError):
         conn.run(query)
+    assert query.run.call_count == 1
 
 
 def test_check_replica_set_not_enabled(mongodb_connection):