Comment 0 for bug 1934937

When performing a heartbeat to rabbit (inside a nova-compute process), there is a greenlet error which causes a hard crash.

I'm not exactly sure what details are relevant, but can provide more info if there's something that will be useful!

This is on RHEL7 (essentially... somewhat custom image based on it)

Log snippet:

```
2021-07-07 19:34:52,686 DEBUG [oslo.messaging._drivers.impl_rabbit] /opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/oslo_messaging/_drivers/impl_rabbit.py:__init__:608 [279fc413-9d7c-4fad-89e8-8de308658947] Connecting to AMQP server on 127.0.0.1:5671
2021-07-07 19:34:52,699 DEBUG [amqp.connection.Connection.heartbeat_tick] /opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/amqp/connection.py:heartbeat_tick:726 heartbeat_tick : for connection 79f7cf4331b34cb0a2e3608281076773
2021-07-07 19:34:52,699 DEBUG [amqp.connection.Connection.heartbeat_tick] /opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/amqp/connection.py:heartbeat_tick:740 heartbeat_tick : Prev sent/recv: None/None, now - 6/6, monotonic - 9634.717472491, last_heartbeat_sent - 9634.717470288, heartbeat int. - 60 for connection 79f7cf4331b34cb0a2e3608281076773
2021-07-07 19:34:52,700 DEBUG [amqp.connection.Connection.heartbeat_tick] /opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/amqp/connection.py:heartbeat_tick:726 heartbeat_tick : for connection 79f7cf4331b34cb0a2e3608281076773
2021-07-07 19:34:52,701 DEBUG [amqp.connection.Connection.heartbeat_tick] /opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/amqp/connection.py:heartbeat_tick:740 heartbeat_tick : Prev sent/recv: 6/6, now - 6/6, monotonic - 9634.719438155, last_heartbeat_sent - 9634.717470288, heartbeat int. - 60 for connection 79f7cf4331b34cb0a2e3608281076773
2021-07-07 19:34:52,718 DEBUG [amqp] /opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/amqp/connection.py:_on_start:382 Start from server, version: 0.9, properties: {'capabilities': {'publisher_confirms': True, 'exchange_exchange_bindings': True, 'basic.nack': True, 'consumer_cancel_notify': True, 'connection.blocked': True, 'consumer_priorities': True, 'authentication_failure_close': True, 'per_consumer_qos': True, 'direct_reply_to': True}, 'cluster_name': '<email address hidden>', 'copyright': 'Copyright (c) 2007-2020 VMware, Inc. or its affiliates.', 'information': 'Licensed under the MPL 1.1. Website: https://rabbitmq.com', 'platform': 'Erlang/OTP 23.0.2', 'product': 'RabbitMQ', 'version': '3.8.5'}, mechanisms: [b'PLAIN', b'AMQPLAIN', b'EXTERNAL'], locales: ['en_US']
2021-07-07 19:34:52,719 DEBUG [amqp] /opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/amqp/channel.py:__init__:104 using channel_id: 1
2021-07-07 19:34:52,720 DEBUG [amqp] /opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/amqp/channel.py:_on_open_ok:444 Channel open
2021-07-07 19:34:52,721 DEBUG [amqp.connection.Connection.heartbeat_tick] /opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/amqp/connection.py:heartbeat_tick:726 heartbeat_tick : for connection c0299792d20e42a2b0a17d037d7d3058
Traceback (most recent call last):
File "/opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/eventlet/hubs/hub.py", line 476, in fire_timers
timer()
File "/opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/eventlet/hubs/timer.py", line 59, in __call__
cb(*args, **kw)
File "/opt/openstack/venv/nova-23.0.20031033070/lib/python3.8/site-packages/eventlet/semaphore.py", line 152, in _do_acquire
waiter.switch()
greenlet.error: cannot switch to a different thread
```

Versions:

```
oslo.messaging==12.7.1
nova==23.0.2 (packaged locally from stable/wallaby as of July 3, 2021)
```