Comment 3 for bug 1621451

It's due to inconsistency of dragonflow version of neutron server and compute node.
Pub/sub message sent by neutron server can't be parsed successfully by compute node.
Compute node then throw an exception like this:

dragonflow.db.pubsub_drivers.redis_db_pubsub_driver [-] subscriber listening task lost connection string indices must be integers

And generate a "dbstart" event and push it to northbound message queue:

dragonflow.db.api_nb [-] Pushing Update to Queue: Action:dbrestart, Table:None, Key:None Value:False Topic:None

Every time when receive a pub/sub mesg, these logs will be printed.

By updating to one same version, this problem can be solved.
So I think this bug can be closed.