I'm receiving this error:
sqlalchemy.exc.TimeoutError: QueuePool limit of size 5 overflow 10 reached,
connection timed out, timeout 30
I'm curious how SQLAlchemy manages database connections. I've pasted below
some psuedo-code to simplify the application.
# Create an engine
engine = create_engine('whatever')
# Create a scoped session factory
factory = sqlalchemy.orm.sessionmaker(bind=engine)
factory = sqlalchemy.orm.scoped_session(factory, scopefunc=
_app_ctx_stack.__ident_func__)
# Handle websocket connection
def my_websocket(ws):
while True:
# yield after arbitrary amount of time
model_id = yield_from_redis()
# Use the session to query the model.
session = factory()
model = session.query(SomeModel).get(model_id)
ws.send(model.seralized)
# breakout or whatever
factory.remove()
The engine and factory are being created once on a singleton. The session
is being created each time its needed. Anytime I need a session, I call
factory(). This hasn't been a problem on the HTTP server (I call remove()
after each request) but since websockets are so long lived, I assume that
creating all these session instances are somehow causing the overflow.
Should I be closing that session sooner? I assume thats the case but I'm
asking because I want to make sure the code is as stable as possible.
--
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The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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