No handler found if logging occurs before logging is ready

[Joe D'Andrea]

It's not unusual to see this pattern (e.g., for heat-api):

  logging.register_options(cfg.CONF)
  cfg.CONF(project='heat', prog='heat-api',
    version=version.version_info.version_string())

Let's say oslo_config discovers a deprecated option:

  if self.deprecated_for_removal and not self._logged_deprecation:
      self._logged_deprecation = True
      pretty_group = group_name or 'DEFAULT'
      LOG.warning('Option "%s" from group "%s" is deprecated for '
                  'removal. Its value may be silently ignored in the '
                  'future.', self.dest, pretty_group)

In this case it logs a warning ... except logging isn't ready yet (the default handlers aren't in place at this point), resulting in:

  No handlers could be found for logger "oslo_config.cfg"

After observing other kilo/liberty installations/upgrades, it looks like this is happening across a variety of projects. That means there are warnings and errors that aren't being surfaced.

[Joe D'Andrea (jdandrea)]

Patch submitted for review:
https://review.openstack.org/#/c/245303

[Joe D'Andrea (jdandrea)]

Switching back per discussion w/dims and adjusting commit. (Thanks for your help on this, Davanum!)

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/245303
Committed: https://git.openstack.org/cgit/openstack/oslo.log/commit/?id=ed9d276af0a54807ebf0ddfb8c9dbafedae24db8
Submitter: Jenkins
Branch: master

commit ed9d276af0a54807ebf0ddfb8c9dbafedae24db8
Author: Joe D'Andrea <email address hidden>
Date: Fri Nov 13 19:23:50 2015 +0000

    Log to sys.stderr to avoid "No handlers could be found..."

    On occasion, logging can occur before logging is ready, resulting
    in unseen warnings/errors, for instance in oslo_config. To avoid
    this, we temporarily log to sys.stderr until things are ready.

    Change-Id: I9a3ce94881d1cdaddfe5a616dca0bdbf5326eddc
    Closes-Bug: 1516128