[Ceilometer] Remove Eventlet from the API Server

[Vitaly Gusev]

Upstream blueprint: https://blueprints.launchpad.net/ceilometer/+spec/remove-web-eventlet

As of Kilo, the WSGI application which provides the Ceilometer API can be run in two fundamentally different ways:
- As a Python command that runs a Werkzeug-based web server that is monkeypatched to use eventlet.
-As a WSGI application hosted by any WSGI server, often Apache + mod wsgi.

Hosting the server application in a dedicate WSGI host has performance, configuration and scaling advantages. Running the command line service, while convenient for simple testing, can result in difficult to diagnose bugs and unusual behaviors when it is monkeypatched to use eventlet. Since the Werkzeug server can (and as written, does) provide support for multi-process and multi-threaded interactions, the inclusion of eventlet should be removed.

[Roman Podoliaka (rpodolyaka)]

Vitaly, are you proposing to host Ceilometer WSGI app by mod_wsgi here? This should be a BP or a user story. It's too late to do this in 8.0, IMO.

[Ivan Berezovskiy (iberezovskiy)]

I suggest to move this task to 9.0. We will have more time to test it. For 8.0 it is too late and risky.

[Denis Meltsaykin (dmeltsaykin)]

~2 years without any progress. Closing as Won't Fix.