list os-service causing reconnects to memcached all the time

[norman shen]

Description
===========

we are running a victoria openstack cluster (python3). and I observe that everytime when an openstack compute service list executed, nova-api will create a new connection to memcache. Actually there are several reasons to cause this behavior

1. when running natively with eventlet's wsgi server, everytime a new coroutine is created to host web request and this causes keystonemiddle auth_token which uses python-memcached to reconnect to memcahced all the time
2. os-services will trigger nova.availability_zones.set_availability_zones and it will update cache every time, since cellv2 is enabled, this method is running in an co-routine as well
3. python-memcached's Client is inheriting from threading.local which will be monkey_patched to use eventlet's implementation and thus for every co-routine context it will create a new connection

Steps to reproduce
==================

1. Patch def _get_socket and print connection
2. execute openstack compute service list

Expected result
===============

Maintain stable connections to memcached

Actual result
=============

Reconnects

Environment
===========

1. devstack victoria openstack

[melanie witt (melwitt)]

Hi, running nova-api or nova-metadata-api using the eventlet server was deprecated in the Rocky release [1] and is no longer supported.

API services can and should be run using WSGI servers such as uwsgi or mod_wsgi:

https://docs.openstack.org/nova/latest/user/wsgi.html

If you encounter issues running under one of these servers, please feel free to re-open this bug or open a new bug and we will take a look.

[1] https://docs.openstack.org/releasenotes/nova/rocky.html#deprecation-notes

[norman shen (jshen28)]

Hmm, then I think openstack-helm should stop using eventlet wsgi server. Besides, this os-service stuff is not related to eventlet wsgi server at all. It could be reproduced through devstack which uses uwsgi as wsgi server.