Merge pull request #227 from Uninett/uninett.fix_session_sideeffect

Put sessionmaker code in a function

src/cnaas_nms/db/session.py

@@ -7,6 +7,7 @@
 from sqlalchemy.pool import NullPool
 from redis import StrictRedis
 
+_sessionmaker = None
 
 def get_dbdata(config='/etc/cnaas-nms/db_config.yml'):
     with open(config, 'r') as db_file:
@@ -31,16 +32,19 @@ def get_sqlalchemy_conn_str(**kwargs) -> str:
         f"{db_data['hostname']}:{db_data['port']}/{db_data['database']}"
     )
 
-
-conn_str = get_sqlalchemy_conn_str()
-engine = create_engine(conn_str, pool_size=50, max_overflow=50)
-connection = engine.connect()
-Session = sessionmaker(bind=engine)
+def _get_session():
+    global _sessionmaker
+    if _sessionmaker is None:
+        conn_str = get_sqlalchemy_conn_str()
+        engine = create_engine(conn_str, pool_size=50, max_overflow=50)
+        engine.connect()
+        _sessionmaker = sessionmaker(bind=engine)
+    return _sessionmaker()
 
 
 @contextmanager
 def sqla_session(**kwargs):
-    session = Session()
+    session = _get_session()
     try:
         yield session
         session.commit()