nova/nova/scheduler/request_filter.py

#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

import functools

import os_traits
from oslo_log import log as logging
from oslo_utils import timeutils

import nova.conf
from nova import exception
from nova.i18n import _
from nova import objects


CONF = nova.conf.CONF
LOG = logging.getLogger(__name__)
TENANT_METADATA_KEY = 'filter_tenant_id'


def trace_request_filter(fn):
    @functools.wraps(fn)
    def wrapper(ctxt, request_spec):
        timer = timeutils.StopWatch()
        ran = False
        with timer:
            try:
                ran = fn(ctxt, request_spec)
            finally:
                if ran:
                    # Only log info if the filter was enabled and not
                    # excluded for some reason
                    LOG.debug('Request filter %r took %.1f seconds',
                        fn.__name__, timer.elapsed())
        return ran
    return wrapper


@trace_request_filter
def require_tenant_aggregate(ctxt, request_spec):
    """Require hosts in an aggregate based on tenant id.

    This will modify request_spec to request hosts in an aggregate
    defined specifically for the tenant making the request. We do that
    by looking for a nova host aggregate with metadata indicating which
    tenant it is for, and passing that aggregate uuid to placement to
    limit results accordingly.
    """

    enabled = CONF.scheduler.limit_tenants_to_placement_aggregate
    agg_required = CONF.scheduler.placement_aggregate_required_for_tenants
    if not enabled:
        return False

    aggregates = objects.AggregateList.get_by_metadata(
        ctxt, value=request_spec.project_id)
    aggregate_uuids_for_tenant = set([])
    for agg in aggregates:
        for key, value in agg.metadata.items():
            if key.startswith(TENANT_METADATA_KEY):
                aggregate_uuids_for_tenant.add(agg.uuid)
                break

    if aggregate_uuids_for_tenant:
        if ('requested_destination' not in request_spec or
                request_spec.requested_destination is None):
            request_spec.requested_destination = objects.Destination()
        destination = request_spec.requested_destination
        destination.require_aggregates(aggregate_uuids_for_tenant)
        LOG.debug('require_tenant_aggregate request filter added '
                  'aggregates %s for tenant %r',
                  ','.join(aggregate_uuids_for_tenant),
                  request_spec.project_id)
    elif agg_required:
        LOG.warning('Tenant %(tenant)s has no available aggregates',
                    {'tenant': request_spec.project_id})
        raise exception.RequestFilterFailed(
            reason=_('No hosts available for tenant'))

    return True


@trace_request_filter
def map_az_to_placement_aggregate(ctxt, request_spec):
    """Map requested nova availability zones to placement aggregates.

    This will modify request_spec to request hosts in an aggregate that
    matches the desired AZ of the user's request.
    """
    if not CONF.scheduler.query_placement_for_availability_zone:
        return False

    az_hint = request_spec.availability_zone
    if not az_hint:
        return False

    aggregates = objects.AggregateList.get_by_metadata(ctxt,
                                                       key='availability_zone',
                                                       value=az_hint)
    if aggregates:
        if ('requested_destination' not in request_spec or
                request_spec.requested_destination is None):
            request_spec.requested_destination = objects.Destination()
        agg_uuids = [agg.uuid for agg in aggregates]
        request_spec.requested_destination.require_aggregates(agg_uuids)
        LOG.debug('map_az_to_placement_aggregate request filter added '
                  'aggregates %s for az %r',
                  ','.join(agg_uuids),
                  az_hint)

    return True


@trace_request_filter
def require_image_type_support(ctxt, request_spec):
    """Request type-specific trait on candidates.

    This will modify the request_spec to request hosts that support the
    disk_format of the image provided.
    """
    if not CONF.scheduler.query_placement_for_image_type_support:
        return False

    if request_spec.is_bfv:
        # We are booting from volume, and thus compute node image
        # disk_format support does not matter.
        return False

    disk_format = request_spec.image.disk_format
    trait_name = 'COMPUTE_IMAGE_TYPE_%s' % disk_format.upper()
    if not hasattr(os_traits, trait_name):
        LOG.error(('Computed trait name %r is not valid; '
                   'is os-traits up to date?'), trait_name)
        return False

    # NOTE(danms): We are using the transient flavor in the request spec
    # to add the trait that we need. We make sure that we reset the dirty-ness
    # of this field to avoid persisting it.
    request_spec.flavor.extra_specs['trait:%s' % trait_name] = 'required'
    request_spec.obj_reset_changes(fields=['flavor'], recursive=True)

    LOG.debug('require_image_type_support request filter added required '
              'trait %s', trait_name)

    return True


@trace_request_filter
def compute_status_filter(ctxt, request_spec):
    """Pre-filter compute node resource providers using COMPUTE_STATUS_DISABLED

    The ComputeFilter filters out hosts for compute services that are
    disabled. Compute node resource providers managed by a disabled compute
    service should have the COMPUTE_STATUS_DISABLED trait set and be excluded
    by this mandatory pre-filter.
    """
    # We're called before scheduler utils resources_from_request_spec builds
    # the RequestGroup stuff which gets used to form the
    # GET /allocation_candidates call, so mutate the flavor for that call but
    # don't persist the change.
    trait_name = os_traits.COMPUTE_STATUS_DISABLED
    request_spec.flavor.extra_specs['trait:%s' % trait_name] = 'forbidden'
    request_spec.obj_reset_changes(fields=['flavor'], recursive=True)
    LOG.debug('compute_status_filter request filter added forbidden '
              'trait %s', trait_name)
    return True


ALL_REQUEST_FILTERS = [
    require_tenant_aggregate,
    map_az_to_placement_aggregate,
    require_image_type_support,
    compute_status_filter,
]


def process_reqspec(ctxt, request_spec):
    """Process an objects.ReqestSpec before calling placement.

    :param ctxt: A RequestContext
    :param request_spec: An objects.RequestSpec to be inspected/modified
    """
    for filter in ALL_REQUEST_FILTERS:
        filter(ctxt, request_spec)