RFE: Add CONF.trace option

[Matt Riedemann]

There is a LOG.trace method and a TRACE level:

https://github.com/openstack/oslo.log/blob/d56c3e941c6c7f5861311cae54625551053f2e26/oslo_log/handlers.py#L33

But no way to configure it's usage, like we have for CONF.debug and CONF.verbose.

I think the only way you can get TRACE logging today is via CONF.default_log_levels, but that's not very useful in a service like nova.

We'd have to update oslo_log.log._refresh_root_level also to check CONF.trace:

https://github.com/openstack/oslo.log/blob/d56c3e941c6c7f5861311cae54625551053f2e26/oslo_log/log.py#L330

For something like this:

    if CONF.trace:
        log_root.setLevel(TRACE)

For context, we want to drop some nova-scheduler logs from DEBUG to TRACE here:

https://review.openstack.org/#/c/366283/

But there isn't a way to turn those on.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/366422

[OpenStack Infra (hudson-openstack)]

Change abandoned by Matt Riedemann (<email address hidden>) on branch: master
Review: https://review.openstack.org/366422
Reason: meh

[OpenStack Infra (hudson-openstack)]

Change abandoned by Joshua Harlow (<email address hidden>) on branch: master
Review: https://review.openstack.org/366497

[OpenStack Infra (hudson-openstack)]

Change abandoned by Matt Riedemann (<email address hidden>) on branch: master
Review: https://review.opendev.org/366422
Reason: I guess people can just add nova.scheduler=TRACE to default_log_levels if they want to try and trace that code.

[Takashi Kajinami (kajinamit)]

Closing based on the above comment.