osapi_volume_workers warning when unspecified

[Matthew Edmonds]

Seeing the following warning in cinder logs (juno):

cinder.service [-] Value of config option osapi_volume_workers must be integer greater than 1. Input value ignored.

We're not specifying this in cinder.conf, so the following OpenStack code from cinder/service.py attempts to get the default:

        self.workers = getattr(CONF, '%s_workers' % name,
                               processutils.get_worker_count())
        setup_profiler(name, self.host)

        if self.workers < 1:
            LOG.warn(_("Value of config option %(name)s_workers must be "
                       "integer greater than 1. Input value ignored.") %
                     {'name': name})
            # Reset workers to default
            self.workers = processutils.get_worker_count()

processutils.get_worker_count() looks like this:

    try:
        return multiprocessing.cpu_count()
    except NotImplementedError:
        return 1

and multiprocessing.cpu_count() returns this:

>>> import multiprocessing
>>> multiprocessing.cpu_count()
8

It looks to me like getattr is reading a value for osapi_volume_workers from the conf file even though there is no default set and we didn't specify this in the conf, preventing the default processutils.get_worker_count() from being returned by getattr when it should have been. It still works because processutils.get_worker_count() gets called again, but that shouldn't have been necessary, and neither should the warning (in this case).

[Jay Bryant (jsbryant)]

I have seen this as well.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/122807
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=3d301346a7100e52fe0c319c1c1b5b81a3bc1660
Submitter: Jenkins
Branch: master

commit 3d301346a7100e52fe0c319c1c1b5b81a3bc1660
Author: Jay S. Bryant <email address hidden>
Date: Fri Sep 19 12:46:21 2014 -0500

    Fix unnecessary WSGI worker warning at API startup

    There was a bug in WSGIService in the way that it was
    checking the osapi_volume_workers option. It was using
    getattr() to see if the option was set, if not it was supposed
    to set the value to processutils.get_worker_count(). This,
    however, never happened because getattr interpreted the default
    'None' value to be a value. So, on any system with no value set
    the self.workers < 1 check would be hit and a warning would be
    output.

    Nova had changed their approach to this option to avoid this
    problem. This patch pulls Nova's approach into Cinder for
    consistency. Cinder will now use processutils.get_worker_count()
    if no option is set in /etc/cinder/cinder.conf and when the user sets
    osapi_volume_workers to 0. A negative value will cause an
    InvalidInput exception to be thrown.

    Unittests have been added for this functionality.

    Change-Id: I4ec2fdd0d19195cccffd63cdd1af1b9ca9884c7d
    Closes-bug: #1367454