Hi, Thanks for your reply. I'm using it the way like you. The only
difference is that I am using pyamf instead of PB.
On every request, I delegate required db operations to a class called
Database, similar to these code below.
I used to use scope_session instead of create and close session every
time. But as I said in my earlier mails, they don't work.
These code below seems to work right now. But if you have more
suggestion, I will be very thankful.
#=========================================
def require_session(f):
'''create and close session for each synchronous method'''
def wrapper(model, *args, **kw):
sess = model.Session()
try:
return f(model, sess, *args, **kw)
finally:
sess.close()
return wrapper
class Database()
def __init__(self, conn_str):
self.conn_str = conn_str
self.engine = create_engine(self.conn_str, echo=False)
self.Session = sessionmaker(bind = self.engine,
expire_on_commit=False)
def getObjectById(self, klass, id):
return threads.deferToThread(self._getObjectById, klass, id)
@require_session
def _getObjectById(self, sess, klass, id):
return sess.query(klass).get(id)
#=========================================
On Mar 6, 5:44 am, Jeff FW <jeff...@gmail.com> wrote:
> Don't use scoped_session--you'll run into problems no matter what you
> do. I'm using Perspective Broker from Twisted with SQLAlchemy. I
> make sure to create and commit/rollback a session for *every* PB
> request. It works perfectly, and that's the only way I was really
> able to get it to work in all cases.
>
> Assuming you're using Twisted in a similar way, you could write a
> simple decorator to wrap any functions that need a database session in
> the begin/commit stuff as necessary.
>
> If you can give more details of how you're using Twisted, I might be
> able to offer some more insight.
>
> -Jeff
>
> On Mar 5, 12:33 am, 一首诗 <newpt...@gmail.com> wrote:
>
> > I'm not quite sure, but I think I'm pretty careful of sharing objects
> > between threads.
>
> > 1st, I only cached as few as possible orm objects. I tried to detach
> > them, but I found that if I detach them, I can't access any of their
> > fields any more.
>
> > 2nd, I create new orm objects based on client request, pass them to
> > class Database and then merge them to scoped sessions, change, commit
> > and then discard these objects.
>
> > 3rd, I switch to sqlite frequently to check if there is any database
> > operation outside Database, because sqlite doesn't allow multi-thread
> > access.
>
> > Actually it seems to work until 2 or 3 days ago suddenly cases hang
> > the server.
>
> > Ah, as I've already written lots of code in ORM, I think maybe I
> > should try to change Database to use a dedicated thread to handle all
> > database operations.
>
> > That might be a bottle neck of my application, but I really can't give
> > up orm as these mapper classes are used everywhere in my application.
>
> > On Mar 4, 7:26 pm, 一首诗 <newpt...@gmail.com> wrote:
>
> > > Hi, all
>
> > > I am using sqlalchemy in twisted in my project in the way below.
> > > Defer any database operation so the twisted's main thread won't be
> > > blocked.
>
> > > And I use scoped_session, so that sessions won't have to be created
> > > again and again.
>
> > > ======================================
> > > class Database()
> > > def __init__(self, conn_str):
> > > self.conn_str = conn_str
> > > self.engine = create_engine(self.conn_str, echo=False)
> > > self.Session = scoped_session(sessionmaker(bind = self.engine,
> > > expire_on_commit=False))
>
> > > def getObjectById(self, klass, id):
> > > return threads.deferToThread(self._getObjectById, klass, id)
>
> > > def _getObjectById(self, klass, id):
> > > sess = self.Session()
> > > return sess.query(klass).get(id)
> > > ======================================
>
> > > The code doesn't work. When I limit the thread numbers to 1
>
> > > reactor.suggestThreadPoolSize(1)
>
> > > Everything goes fine. Other wise the server would be blocked and must
> > > be killed by "kill 9 ...".
>
> > > The result conflicts with my understanding of sqlalchemy. Since I
> > > don't share any object between threads, there should be no problem!
>
> > > Ah.... It always have risk to use something you haven't tried
> > > before ....
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