Cinder DriverFilter run_evaluator() should check volume driver name instead of volume backend name

[Chhavi Agarwal]

This defect is raised as a part of discussion on the below blueprint
https://review.openstack.org/#/c/182980/

Huang Zhiteng May 18 6:52 AM

Patch Set 2: Code-Review-1

Chhavi, what you have describe is a bug of DriverFilter. It shouldn't use volume backend name as indicator whether or not to run_evaluator(). A more appropriate check should be checking the volume driver name and probably version. Again, it is just a bug in a non-default filter. It doesn't imply that is how cinder filter scheduler works. Try my previous suggestion with default scheduler filters.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/188543

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/188543
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=b32091192b7af7b0fccab1e078480ec38ada7bcc
Submitter: Jenkins
Branch: master

commit b32091192b7af7b0fccab1e078480ec38ada7bcc
Author: Zhiteng Huang <email address hidden>
Date: Thu Jun 4 11:23:58 2015 -0700

    DriverFilter: don't check volume_backend_name

    Currently DriverFilter checks if host_state.volume_backend_name
    matches type.extra_specs.volume_backend_name. The same check has
    already been done in CapabilitiesFilter and done more thoroughly and
    gracefully, for example, volume_backend_name can be a set of names
    not limited to one to one match. DriverFilter should just do one
    thing, that is evaluating filter_function supplied by backend.

    This change removes the volume_backend_name check from DriverFilter
    without touching its core function, thus has no impact on existing
    documentation because the checking of volume_backend_name is an
    undocumented side-effect of this filter. This change also reduces
    one warning log to debug log when no filter_function found in
    host_state, for the reason it would generate a lot of warning log
    for those backends don't supply filter_function.

    UpgradeImpact:
    DriverFilter had an undocumented side-effect before it evaluates
    filter_function - it checked if volume_backend_name in host_state
    reported by backend matches volume_backend_name in volume type
    extra specs, and if they don't, the backend would fail to pass
    the filter. Now that this side-effect has been removed, it
    would impact users only under following circumstance: 1) user
    enabled DriverFilter but not CapabilitiesFilter; 2) user relied
    on DriverFilter to filter backends based on exact match of
    'volume_backend_name' in type extra spec. If unfortunately this
    is the case for user, enabling CapabilitiesFilter by adding
    it to 'scheduler_default_filters' configure option and restart
    cinder scheduler service then everything should work just fine.
    CapabilitiesFilter actually does a much better job checking
    volume_backend_name.

    Change-Id: Ie5c48587368856faa538eebb1b6611d464bd69bd
    Closes-bug: #1461770