Comment 1 for bug 1566520

I was under the impression that the EXPAND branch could already be executed without shutting down the services. That said, the problem certainly lies with the CONTRACT branches. This feels like a rehash of parts of [1], and as such is part of a much larger solution required to accommodate a no downtime upgrade for the neutron servers. Looking at the DB alone won't suffice to ensure that requests are handled correctly during the upgrade. Please provide a more detailed plan, and break it down into chewable pieces for Newton. I suspect that once you do that the RFE title won't sound like 'Upgrade controllers with no API downtime'.

[1] https://blueprints.launchpad.net/neutron/+spec/online-schema-migrations