Revert "[db] Prefer NullPool for forked SQLAlchemy connections"

This reverts commit f2b1118.

framework/db/db.py

@@ -9,7 +9,7 @@
 
 from sqlalchemy.orm import scoped_session, sessionmaker
 from sqlalchemy import create_engine, exc
-from sqlalchemy.pool import NullPool
+from sqlalchemy.pool import QueuePool
 from sqlalchemy.orm import Session as BaseSession
 
 from framework.utils import FileOperations
@@ -128,7 +128,9 @@ def CreateEngine(self, BaseClass):
                     self._db_settings['DATABASE_IP'],
                     self._db_settings['DATABASE_PORT'],
                     self._db_settings['DATABASE_NAME']),
-                poolclass=NullPool)
+                poolclass=QueuePool,
+                pool_size=5,
+                max_overflow=10)
             BaseClass.metadata.create_all(engine)
             # Fix for forking
             register_after_fork(engine, engine.dispose)