title: o I need to set somehow create_engine put in singleton to be like singleton?
body: <p>On server I am using combination of Tornado and SQLAlchemy (maybe SQLAlchemy is not best choice for async server but it is temporary) I split project and handlers in 10 files/modules.
  In every module I am using <code>session = Session()</code> and <code>session</code> to query database.</p>
  
  <p>common part of every module looks like </p>
  
  <pre><code>...
  import tornado.ioloop
  
  engine = create_engine(DB_URL, echo=False, pool_size=100, pool_recycle=3600)
  Session = sessionmaker(bind=engine)
  
  
  class BaseHandler(tornado.web.RequestHandler):
   ....
  </code></pre>
  
  <p>Do I need to set somehow </p>
  
  <pre><code>engine = create_engine(DB_URL, echo=False, pool_size=100, pool_recycle=3600)
  Session = sessionmaker(bind=engine)
  </code></pre>
  
  <p>to be like singleton, not to create in every module or this is ok way to do things and create sessions.</p>