SQLAlchemy and Falcon - Session Initialization

Question

I am wondering where it would be best to create a restricted session for use in falcon.

From reading the qtyqlalchemy code, in a round he roughly does the following:

from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session, sessionmaker try: from greenlet import get_current as get_ident except ImportError: try: from thread import get_ident except ImportError: from _thread import get_ident connection_uri = 'postgresql://postgres:@localhost:5432/db' engine = create_engine(connection_uri) session_factory = sessionmaker(bind=engine) session_cls = scoped_session(session_factory, scopefunc=get_ident) session = session_cls() 

Will this work for a falcon? Will get_ident func do the right thing when using a gun?

Answer 1

You can use middleware

Example.

• Create an engine, session_factory, and a scoped_session object.

   from sqlalchemy import create_engine from sqlalchemy.orm import scoped_session from sqlalchemy.orm import sessionmaker import settings engine = create_engine( '{engine}://{username}:{password}@{host}:{port}/{db_name}'.format( **settings.POSTGRESQL ) ) session_factory = sessionmaker(bind=engine) Session = scoped_session(session_factory) 

• Create middleware.

   class SQLAlchemySessionManager: """ Create a scoped session for every request and close it when the request ends. """ def __init__(self, Session): self.Session = Session def process_resource(self, req, resp, resource, params): resource.session = self.Session() def process_response(self, req, resp, resource, req_succeeded): if hasattr(resource, 'session'): Session.remove() 

• Register middleware.

   import falcon app = falcon.API(middleware=[ SQLAlchemySessionManager(Session), ]) 

• A session is available in every request.

   import falcon class MyAPI: def on_get(self, req, resp): # You can access self.session here # self.session.add(foo) # self.session.commit()