OpenStack Study: ram_filter.py

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# 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.

from oslo.config import cfg

from nova import db

from nova.openstack.common.gettextutils import _

from nova.openstack.common import log as logging

from nova.scheduler import filters

LOG = logging.getLogger(__name__)

ram_allocation_ratio_opt = cfg.FloatOpt('ram_allocation_ratio',

default=1.5,

help='Virtual ram to physical ram allocation ratio which affects '

'all ram filters. This configuration specifies a global ratio '

'for RamFilter. For AggregateRamFilter, it will fall back to '

'this configuration value if no per-aggregate setting found.')

CONF = cfg.CONF

CONF.register_opt(ram_allocation_ratio_opt)

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class BaseRamFilter(filters.BaseHostFilter):

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def _get_ram_allocation_ratio(self, host_state, filter_properties):

raise NotImplementedError

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def host_passes(self, host_state, filter_properties):

"""Only return hosts with sufficient available RAM."""

instance_type = filter_properties.get('instance_type')

requested_ram = instance_type['memory_mb']

free_ram_mb = host_state.free_ram_mb

total_usable_ram_mb = host_state.total_usable_ram_mb

ram_allocation_ratio = self._get_ram_allocation_ratio(host_state,

filter_properties)

memory_mb_limit = total_usable_ram_mb * ram_allocation_ratio

used_ram_mb = total_usable_ram_mb - free_ram_mb

usable_ram = memory_mb_limit - used_ram_mb

if not usable_ram >= requested_ram:

LOG.debug(_("%(host_state)s does not have %(requested_ram)s MB "

"usable ram, it only has %(usable_ram)s MB usable ram."),

{'host_state': host_state,

'requested_ram': requested_ram,

'usable_ram': usable_ram})

return False

# save oversubscription limit for compute node to test against:

host_state.limits['memory_mb'] = memory_mb_limit

return True

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class RamFilter(BaseRamFilter):

"""Ram Filter with over subscription flag."""

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def _get_ram_allocation_ratio(self, host_state, filter_properties):

return CONF.ram_allocation_ratio

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class AggregateRamFilter(BaseRamFilter):

"""AggregateRamFilter with per-aggregate ram subscription flag.

Fall back to global ram_allocation_ratio if no per-aggregate setting found.

"""

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def _get_ram_allocation_ratio(self, host_state, filter_properties):

context = filter_properties['context'].elevated()

# TODO(uni): DB query in filter is a performance hit, especially for

# system with lots of hosts. Will need a general solution here to fix

# all filters with aggregate DB call things.

metadata = db.aggregate_metadata_get_by_host(

context, host_state.host, key='ram_allocation_ratio')

aggregate_vals = metadata.get('ram_allocation_ratio', set())

num_values = len(aggregate_vals)

if num_values == 0:

return CONF.ram_allocation_ratio

if num_values > 1:

LOG.warning(_("%(num_values)d ratio values found, "

"of which the minimum value will be used."),

{'num_values': num_values})

try:

ratio = float(min(aggregate_vals))

except ValueError as e:

LOG.warning(_("Could not decode ram_allocation_ratio: '%s'"), e)

ratio = CONF.ram_allocation_ratio

return ratio