Probably still caused by rpc timeout to schedule l3 agent task. 

2014-07-18 04:01:21    ERROR [quantum.openstack.common.rpc.amqp] Exception during message handling
 Traceback (most recent call last):
  File "/usr/lib/python2.6/site-packages/quantum/openstack/common/rpc/amqp.py", line 430, in _process_data
    rval = self.proxy.dispatch(ctxt, version, method, **args)
  File "/usr/lib/python2.6/site-packages/quantum/common/rpc.py", line 43, in dispatch
    quantum_ctxt, version, method, **kwargs)
  File "/usr/lib/python2.6/site-packages/quantum/openstack/common/rpc/dispatcher.py", line 133, in dispatch
    return getattr(proxyobj, method)(ctxt, **kwargs)
  File "/usr/lib/python2.6/site-packages/quantum/db/agents_db.py", line 173, in report_state
    plugin.create_or_update_agent(context, agent_state)
  File "/usr/lib/python2.6/site-packages/quantum/db/agents_db.py", line 156, in create_or_update_agent
    context.session.add(agent_db)
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/orm/session.py", line 402, in __exit__
    self.commit()
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/orm/session.py", line 314, in commit
    self._prepare_impl()
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/orm/session.py", line 298, in _prepare_impl
    self.session.flush()
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/orm/session.py", line 1583, in flush
    self._flush(objects)
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/orm/session.py", line 1654, in _flush
    flush_context.execute()
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/orm/unitofwork.py", line 331, in execute
    rec.execute(self)
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/orm/unitofwork.py", line 475, in execute
    uow
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/orm/persistence.py", line 59, in save_obj
    mapper, table, update)
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/orm/persistence.py", line 485, in _emit_update_statements
    execute(statement, params)
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py", line 1449, in execute
    params)
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py", line 1584, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py", line 1698, in _execute_context
    context)
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/engine/base.py", line 1691, in _execute_context
    context)
  File "/usr/lib64/python2.6/site-packages/SQLAlchemy-0.7.8-py2.6-linux-x86_64.egg/sqlalchemy/engine/default.py", line 331, in do_execute
    cursor.execute(statement, parameters)
  File "/usr/lib64/python2.6/site-packages/MySQLdb/cursors.py", line 173, in execute
    self.errorhandler(self, exc, value)
  File "/usr/lib64/python2.6/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue
 OperationalError: (OperationalError) (1205, 'Lock wait timeout exceeded; try restarting transaction') 'UPDATE agents SET heartbeat_timestamp=%s WHERE agents.id = %s' (datetime.datetime(2014, 7, 18, 11, 0, 20, 5080), '3d198f04-8054-4c5b-8864-b4ea51f6f172')
 2014-07-18 04:01:21    DEBUG [quantum.policy] loading policy file at /etc/quantum/policy.json