sqlalchemy的session与线程备忘

http://www.mail-archive.com/[e-mail]/msg07933.html

an example of a typical Session lifecycle as placed in a web 
application is here:

http://www.sqlalchemy.org/docs/04/session.html#unitofwork_contextual_lifespan

theres no "reconnecting" going on explicitly on your end.  the Session 
itself typically lasts for the span of a single web request, after 
which it is either discarded, or closed which releases its resources 
until the next web request where it can be used again.

When using scoped_session(), you automatically get thread local 
behavior out of it so simply calling Session.remove() or 
Session.close() at the end of a request should be sufficient.

So in your code youd want to only call get_database exactly once for 
the entire application, and you'd want to use scoped_session() to 
account for multiple threads.