Goal: 

As a developer, I want run nova-novncproxy with native threading, so that nova will work post Eventlet.

Acceptance Criteria:

• nova-novncproxy works in threading mode
• nova-novncproxy works in Eventlet mode
• nova-novncproxy uses the proper oslo.service backend based on the mode
• at least one upstream CI job exists that runs tempest with nova-novncproxy using threading mode
• novncproxy scales similarly in threading mode as in eventlet mode from both cpu and memory consumption perspective.
• as a special acceptance criteria here I want to only close this ticket when the upstream patches are landed and the nova-next job is running novncproxy in threading mode to all incoming patches.

Note

If during the transformation we hit a scaling issue due the proxy runs one thread per connection and threads are more memory intensive than greenlets we might choose to investigate possible asyncio transformation of novncproxy.