Traceback is dumped when nova-api is run by apache + mod_wsgi

[Takashi Kajinami]

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

We noticed that the following traceback is dumped to error log in httpd when nova-api is run by httpd + mod_wsgi.
This is because nova-api WSGI application attempts to register signal handers for GMR but this is blocked y httpd.
This does not cause any functional problem, but is annoying for operators, and we should consider the way to surpress these warnings.

[Mon Jan 22 06:29:49.889120 2024] [wsgi:warn] [pid 82455:tid 82557] mod_wsgi (pid=82455): Callback registration for signal 12 ignored.
[Mon Jan 22 06:29:49.889918 2024] [wsgi:warn] [pid 82455:tid 82557] File "/var/www/cgi-bin/nova/nova-api", line 52, in <module>
[Mon Jan 22 06:29:49.889937 2024] [wsgi:warn] [pid 82455:tid 82557] application = init_application()
[Mon Jan 22 06:29:49.889955 2024] [wsgi:warn] [pid 82455:tid 82557] File "/usr/lib/python3.9/site-packages/nova/api/openstack/compute/wsgi.py", line 20, in init_application
[Mon Jan 22 06:29:49.889967 2024] [wsgi:warn] [pid 82455:tid 82557] return wsgi_app.init_application(NAME)
[Mon Jan 22 06:29:49.889983 2024] [wsgi:warn] [pid 82455:tid 82557] File "/usr/lib/python3.9/site-packages/nova/api/openstack/wsgi_app.py", line 128, in init_application
[Mon Jan 22 06:29:49.889994 2024] [wsgi:warn] [pid 82455:tid 82557] init_global_data(conf_files, name)
[Mon Jan 22 06:29:49.890027 2024] [wsgi:warn] [pid 82455:tid 82557] File "/usr/lib/python3.9/site-packages/nova/utils.py", line 1133, in wrapper
[Mon Jan 22 06:29:49.890039 2024] [wsgi:warn] [pid 82455:tid 82557] return func(*args, **kwargs)
[Mon Jan 22 06:29:49.890054 2024] [wsgi:warn] [pid 82455:tid 82557] File "/usr/lib/python3.9/site-packages/nova/api/openstack/wsgi_app.py", line 105, in init_global_data
[Mon Jan 22 06:29:49.890065 2024] [wsgi:warn] [pid 82455:tid 82557] gmr.TextGuruMeditation.setup_autorun(
[Mon Jan 22 06:29:49.890080 2024] [wsgi:warn] [pid 82455:tid 82557] File "/usr/lib/python3.9/site-packages/oslo_reports/guru_meditation_report.py", line 155, in setup_autorun
[Mon Jan 22 06:29:49.890091 2024] [wsgi:warn] [pid 82455:tid 82557] cls._setup_signal(signal.SIGUSR2,
[Mon Jan 22 06:29:49.890106 2024] [wsgi:warn] [pid 82455:tid 82557] File "/usr/lib/python3.9/site-packages/oslo_reports/guru_meditation_report.py", line 188, in _setup_signal
[Mon Jan 22 06:29:49.890117 2024] [wsgi:warn] [pid 82455:tid 82557] signal.signal(signum,

Steps to reproduce
==================
* Install httpd
* Add vhost to run nova-api
* Start httpd

Expected result
===============
No traceback appears in error.log

Actual result
=============
Traceback appears in error.log

Environment
===========
This issue wsa initially found in CentOS Stream 9 + RDO master.

httpd-2.4.57-6.el9.x86_64
openstack-nova-api-28.1.0-0.20240111050756.fed1230.el9.noarch
openstack-nova-common-28.1.0-0.20240111050756.fed1230.el9.noarch
openstack-nova-compute-28.1.0-0.20240111050756.fed1230.el9.noarch
openstack-nova-conductor-28.1.0-0.20240111050756.fed1230.el9.noarch
openstack-nova-novncproxy-28.1.0-0.20240111050756.fed1230.el9.noarch
openstack-nova-scheduler-28.1.0-0.20240111050756.fed1230.el9.noarch

Logs & Configs
==============
Example log:
https://cab2ad659632c7fadcca-8cee698db2ecce5ea7fdb78c34542529.ssl.cf1.rackcdn.com/906237/1/check/puppet-openstack-integration-7-scenario001-tempest-centos-9-stream/29e7836/logs/apache/nova_api_wsgi_error_ssl.txt