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# Copyright (c) 2012 OpenStack Foundation
# All Rights Reserved.
# 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
# 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.
"""Availability zone helper functions."""
import collections
from nova import cache_utils
import nova.conf
from nova import objects
# NOTE(vish): azs don't change that often, so cache them for an hour to
# avoid hitting the db multiple times on every request.
MC = None
CONF = nova.conf.CONF
def _get_cache():
global MC
if MC is None:
MC = cache_utils.get_client(expiration_time=AZ_CACHE_SECONDS)
return MC
def reset_cache():
"""Reset the cache, mainly for testing purposes and update
availability_zone for host aggregate
global MC
MC = None
def _make_cache_key(host):
return "azcache-%s" % host
def _build_metadata_by_host(aggregates, hosts=None):
if hosts and not isinstance(hosts, set):
hosts = set(hosts)
metadata = collections.defaultdict(set)
for aggregate in aggregates:
for host in aggregate.hosts:
if hosts and host not in hosts:
return metadata
def set_availability_zones(context, services):
# Makes sure services isn't a sqlalchemy object
services = [dict(service) for service in services]
hosts = set([service['host'] for service in services])
aggregates = objects.AggregateList.get_by_metadata_key(context,
'availability_zone', hosts=hosts)
metadata = _build_metadata_by_host(aggregates, hosts=hosts)
# gather all of the availability zones associated with a service host
for service in services:
az = CONF.internal_service_availability_zone
if service['topic'] == "compute":
if metadata.get(service['host']):
az = u','.join(list(metadata[service['host']]))
az = CONF.default_availability_zone
# update the cache
service['host'], az)
service['availability_zone'] = az
return services
def get_host_availability_zone(context, host):
aggregates = objects.AggregateList.get_by_host(context, host,
if aggregates:
az = aggregates[0].metadata['availability_zone']
az = CONF.default_availability_zone
return az
def update_host_availability_zone_cache(context, host, availability_zone=None):
if not availability_zone:
availability_zone = get_host_availability_zone(context, host)
cache = _get_cache()
cache_key = _make_cache_key(host)
cache.set(cache_key, availability_zone)
def get_availability_zones(context, hostapi, get_only_available=False,
with_hosts=False, services=None):
"""Return available and unavailable zones on demand.
:param context: nova auth RequestContext
:param hostapi: nova.compute.api.HostAPI instance
:param get_only_available: flag to determine whether to return
available zones only, default False indicates return both
available zones and not available zones, True indicates return
available zones only
:param with_hosts: whether to return hosts part of the AZs
:type with_hosts: bool
:param services: list of services to use; if None, enabled services will be
retrieved from all cells with zones set
if services is None:
services = hostapi.service_get_all(
context, set_zones=True, all_cells=True)
enabled_services = []
disabled_services = []
for service in services:
if not service.disabled:
if with_hosts:
return _get_availability_zones_with_hosts(
enabled_services, disabled_services, get_only_available)
return _get_availability_zones(
enabled_services, disabled_services, get_only_available)
def _get_availability_zones(
enabled_services, disabled_services, get_only_available=False):
available_zones = {
service['availability_zone'] for service in enabled_services
if get_only_available:
return sorted(available_zones)
not_available_zones = {
service['availability_zone'] for service in disabled_services
if service['availability_zone'] not in available_zones
return sorted(available_zones), sorted(not_available_zones)
def _get_availability_zones_with_hosts(
enabled_services, disabled_services, get_only_available=False):
available_zones = collections.defaultdict(set)
for service in enabled_services:
if get_only_available:
return sorted(available_zones.items())
not_available_zones = collections.defaultdict(set)
for service in disabled_services:
if service['availability_zone'] in available_zones:
return sorted(available_zones.items()), sorted(not_available_zones.items())
def get_instance_availability_zone(context, instance):
"""Return availability zone of specified instance."""
host = if 'host' in instance else None
if not host:
# Likely hasn't reached a viable compute node yet so give back the
# desired availability_zone in the instance record if the boot request
# specified one.
az = instance.get('availability_zone')
return az
cache_key = _make_cache_key(host)
cache = _get_cache()
az = cache.get(cache_key)
az_inst = instance.get('availability_zone')
if az_inst is not None and az != az_inst:
# NOTE(sbauza): Cache is wrong, we need to invalidate it by fetching
# again the right AZ related to the aggregate the host belongs to.
# As the API is also calling this method for setting the instance
# AZ field, we don't need to update the field.
# This case can happen because the cache is populated before the
# instance has been assigned to the host so that it would keep the
# former reference which was incorrect. Instead of just taking the
# instance AZ information for refilling the cache, we prefer to
# invalidate the cache and fetch it again because there could be some
# corner cases where this method could be called before the instance
# has been assigned to the host also.
az = None
if not az:
elevated = context.elevated()
az = get_host_availability_zone(elevated, host)
cache.set(cache_key, az)
return az