Comment 1 for bug 1288438

The issue seems to stem from the checkout pool event handler in openstack/common/db/sqlalchemy/session.py. Each time a connection is requested from the pool this event handler checks that the connection is alive by running a query. In our case this query times out after 'read_timeout' seconds and the connection is recycled in the pool. This happens for each connection in the pool one at a time.

If we dispose of all connections in the pool when any connection fails the problem goes away. This does not seem like a good solution. So far in my testing I have only encountered this issue with neutron even though all services share this same code. I'm not sure why that's the case.