DetachedInstanceError when binding network to agent

[Eugene Nikanorov]

TRACE neutron.db.agentschedulers_db Traceback (most recent call last):
TRACE neutron.db.agentschedulers_db File "/usr/lib/python2.7/dist-packages/neutron/db/agentschedulers_db.py", line 192, in _schedule_network
TRACE neutron.db.agentschedulers_db agents = self.schedule_network(context, network)
TRACE neutron.db.agentschedulers_db File "/usr/lib/python2.7/dist-packages/neutron/db/agentschedulers_db.py", line 400, in schedule_network
TRACE neutron.db.agentschedulers_db self, context, created_network)
TRACE neutron.db.agentschedulers_db File "/usr/lib/python2.7/dist-packages/neutron/scheduler/dhcp_agent_scheduler.py", line 91, in schedule
TRACE neutron.db.agentschedulers_db self._schedule_bind_network(context, chosen_agents, network['id'])
TRACE neutron.db.agentschedulers_db File "/usr/lib/python2.7/dist-packages/neutron/scheduler/dhcp_agent_scheduler.py", line 51, in _schedule_bind_network
TRACE neutron.db.agentschedulers_db LOG.info(_('Agent %s already present'), agent)
...
TRACE neutron.db.agentschedulers_db DetachedInstanceError: Instance <Agent at 0x5ff1710> is not bound to a Session; attribute refresh operation cannot proceed
2015-02-21 14:45:15.927 1417 TRACE neutron.db.agentschedulers_db

Need to print saved agent_id instead of using db object.

[Eugene Nikanorov (enikanorov)]

Apparently this is only reproducible under mysql. There is a unit test for exact conditions that lead to this trace, but no such exception is thrown.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/158242

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/158242
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=4d4de151e9a0edd86b8ce5b055e56a5784d5c08f
Submitter: Jenkins
Branch: master

commit 4d4de151e9a0edd86b8ce5b055e56a5784d5c08f
Author: Eugene Nikanorov <email address hidden>
Date: Mon Feb 23 13:29:08 2015 +0300

    Avoid DetachedInstanceError after session rollback

    In some cases this exception is thrown while accessing Agent
    object from logging statement after a transaction was rolled back.
    There is a unit test that covers thsi code patch, but the issue
    is not reproducible with sqlite.
    Just avoid accessing db object after session had been closed.

    Change-Id: Iff6b72156b08f177bd0c71f6ba93d3bf46c82fa4
    Closes-Bug: #1424578