Comment 8 for bug 1905115

I would not agree with "cost almost negligible".

- Complexity added to metadata agent
  - bugs will be introduced
- Load on message bus
  - will this affect how quickly we can provision?
- Support of new technology
  - haproxy today, but haproxy2 is already out
- New API calls for users
  - Not a zero cost to learn how to program this new feature

The point I'm trying to make is we have ways to do what you want today, so you need to give a compelling reason that this is better.

And to respond to one of your points.

- "I want to say the list of external services should be configred in neutron-metadata-agent configration file, and neutron-server configuration file can specify that enable which external services channels."

I don't think any new feature should only be configurable via the config file, that isn't scalable at all, since for every change it has to be restarted, which causes control (and possibly data plan) outages.