Getting "Invalid cursor state (0)" when running concurrent requests (SQLAlchemy & wsgi/python)

Question

I'm using SQLAlchemy in WSGI python web app to query the database. If I do two concurrent requests, the second request invariably throws an exception, with SQL Server stating

[24000] [FreeTDS][SQL Server]Invalid cursor state (0) (SQLExecDirectW)

Unfortunately it looks like I can't use caching to prevent additional requests to the database. Is there another way to resolve this issue? Ideally using native python libraries (i.e. not relying on another python module)?

The only thing I can think of is using threads to put a lock on the function making the database queries, but I'm worried this will slow down the app.

Is there anything else that can be done? Is this a configuration issue?

I'm using FreeTDS v0.91 on a Centos 5.9 server, connecting to MS SQL Server 2008.

The webapp is based on Paste.

Answer 1

Are your two concurrent requests using different database connections? DBAPI connections are not generally threadsafe. At the ORM level, you'd make sure you're using session per request so that each request has its own Session and therefore dedicated DBAPI connection.