scaling governors are optional for some OS platforms

[Sylvain Bauza]

Some OS platforms don't use cpufreq, so operators should be able to just offline their CPUs.

For the moment, even if the config option CPU management strategy is 'cpu_state', we return an exception if so.

Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service Traceback (most recent call last):
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service File "/opt/stack/nova/nova/filesystem.py", line 37, in read_sys
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service with open(os.path.join(SYS, path), mode='r') as data:
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service FileNotFoundError: [Errno 2] No such file or directory: '/sys/devices/system/cpu/cpu1/cpufreq/scaling_governor'
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service The above exception was the direct cause of the following exception:
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service Traceback (most recent call last):
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service File "/usr/local/lib/python3.10/dist-packages/oslo_service/service.py", line 806, in run_service
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service service.start()
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service File "/opt/stack/nova/nova/service.py", line 162, in start
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service self.manager.init_host(self.service_ref)
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service File "/opt/stack/nova/nova/compute/manager.py", line 1608, in init_host
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service self.driver.init_host(host=self.host)
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service File "/opt/stack/nova/nova/virt/libvirt/driver.py", line 825, in init_host
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service libvirt_cpu.validate_all_dedicated_cpus()
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service File "/opt/stack/nova/nova/virt/libvirt/cpu/api.py", line 143, in validate_all_dedicated_cpus
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service governors.add(pcpu.governor)
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service File "/opt/stack/nova/nova/virt/libvirt/cpu/api.py", line 63, in governor
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service return core.get_governor(self.ident)
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service File "/opt/stack/nova/nova/virt/libvirt/cpu/core.py", line 69, in get_governor
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service return filesystem.read_sys(
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service File "/opt/stack/nova/nova/filesystem.py", line 40, in read_sys
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service raise exception.FileNotFound(file_path=path) from exc
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service nova.exception.FileNotFound: File /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor could not be found.
Jun 05 14:47:45 sbauza-dev2 nova-compute[75181]: ERROR oslo_service.service

Let's just to support the CPU state if so.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/c/openstack/nova/+/885352

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/nova/+/885352
Committed: https://opendev.org/openstack/nova/commit/2c4421568ea62e66257b55c08092de3e0303fb0a
Submitter: "Zuul (22348)"
Branch: master

commit 2c4421568ea62e66257b55c08092de3e0303fb0a
Author: Sylvain Bauza <email address hidden>
Date: Tue Jun 6 11:56:32 2023 +0200

    cpu: make governors to be optional

    Change-Id: Ifb7d001cfdb95b1b0aa29f45c0ef71c0673e1760
    Closes-Bug: #2023018

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/2023.2
Review: https://review.opendev.org/c/openstack/nova/+/905673

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/2023.1
Review: https://review.opendev.org/c/openstack/nova/+/905676

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/nova/+/905673
Committed: https://opendev.org/openstack/nova/commit/891d1773a26082e3f24ec6583f843b39a50bf76d
Submitter: "Zuul (22348)"
Branch: stable/2023.2

commit 891d1773a26082e3f24ec6583f843b39a50bf76d
Author: Sylvain Bauza <email address hidden>
Date: Tue Jun 6 11:56:32 2023 +0200

    cpu: make governors to be optional

    Change-Id: Ifb7d001cfdb95b1b0aa29f45c0ef71c0673e1760
    Closes-Bug: #2023018
    (cherry picked from commit 2c4421568ea62e66257b55c08092de3e0303fb0a)

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/nova/+/905676
Committed: https://opendev.org/openstack/nova/commit/5c33bd4dfc8c1fcf3eecd656130408fb0a5a3bc5
Submitter: "Zuul (22348)"
Branch: stable/2023.1

commit 5c33bd4dfc8c1fcf3eecd656130408fb0a5a3bc5
Author: Sylvain Bauza <email address hidden>
Date: Tue Jun 6 11:56:32 2023 +0200

    cpu: make governors to be optional

    Change-Id: Ifb7d001cfdb95b1b0aa29f45c0ef71c0673e1760
    Closes-Bug: #2023018
    (cherry picked from commit 2c4421568ea62e66257b55c08092de3e0303fb0a)
    (cherry picked from commit 891d1773a26082e3f24ec6583f843b39a50bf76d)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/nova 29.0.0.0rc1 release candidate.