Sqlalchemy connection pool

Sqlalchemy's pool_size = 5
The pool is stored in the remote connection with the data volume,
Use C1 = engine. Connect () or
Session = scoped_session (sessionmaker (BIND = engine ))
Will be used to build the connection, and the step for building the connection
1. check whether there is a response in the pool. If yes, the response is returned.
2. If the pool does not have any available connections, a new connection is established.
When you use engine. Close () or
Session2.commit (), session2.rollback (), session2.close ()
Then, the response is returned to the pool.

Http://simple-is-better.com/news/651

The article says that we need to add the finally web. CTX. Orm. Commit ()
Web. CTX. Orm. Close () # <=-close the session, or use. Remove ()
I personally think this is not necessary, because the user uses Web. CTX. Orm. Commit ()

#!/usr/bin/env pythonfrom sqlalchemy import create_engineengine = create_engine("mysql://root:liukesun@172.17.22.131/testdb", pool_size=5,echo_pool=True)c1 = engine.connect()c2 = engine.connect()c3 = engine.connect()c1.close()c2.close()c3.close()# pool size is now three.raw_input()for i in xrange(10):    c = engine.connect()    print c.execute("select 1").fetchall()    c.close()

import stringimport randomimport webfrom sqlalchemy.orm import scoped_session, sessionmakerfrom models import *urls = (    "/", "add",    "/view", "view")def load_sqla(handler):    web.ctx.orm = scoped_session(sessionmaker(bind=engine))    try:        return handler()    except web.HTTPError:       web.ctx.orm.commit()       raise    except:        web.ctx.orm.rollback()        raise    finally:        web.ctx.orm.commit()        # If the above alone doesn't work, uncomment         # the following line:        #web.ctx.orm.expunge_all() app = web.application(urls, locals())app.add_processor(load_sqla)class add:    def GET(self):        web.header('Content-type', 'text/html')        fname = "".join(random.choice(string.letters) for i in range(4))        lname = "".join(random.choice(string.letters) for i in range(7))        u = User(name=fname                ,fullname=fname + ' ' + lname                ,password =542)        web.ctx.orm.add(u)        return "added:" + web.websafe(str(u)) \                            + "<br/>" \                            + '<a href="/view">view all</a>'class view:    def GET(self):        web.header('Content-type', 'text/plain')        return "\n".join(map(str, web.ctx.orm.query(User).all()))if __name__ == "__main__":    app.run()