/
availability_zones.py
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/
availability_zones.py
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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
#
# 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.
"""Availability zone helper functions."""
import collections
import six
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.
AZ_CACHE_SECONDS = 60 * 60
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):
if six.PY2:
host = host.encode('utf-8')
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:
continue
metadata[host].add(list(aggregate.metadata.values())[0])
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']]))
else:
az = CONF.default_availability_zone
# update the cache
update_host_availability_zone_cache(context,
service['host'], az)
service['availability_zone'] = az
return services
def get_host_availability_zone(context, host):
aggregates = objects.AggregateList.get_by_host(context, host,
key='availability_zone')
if aggregates:
az = aggregates[0].metadata['availability_zone']
else:
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.delete(cache_key)
cache.set(cache_key, availability_zone)
def get_availability_zones(context, get_only_available=False,
with_hosts=False):
"""Return available and unavailable zones on demand.
: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
"""
enabled_services = objects.ServiceList.get_all(context, disabled=False,
set_zones=True)
available_zones = []
for (zone, host) in [(service['availability_zone'], service['host'])
for service in enabled_services]:
if not with_hosts and zone not in available_zones:
available_zones.append(zone)
elif with_hosts:
_available_zones = dict(available_zones)
zone_hosts = _available_zones.setdefault(zone, set())
zone_hosts.add(host)
# .items() returns a view in Py3, casting it to list for Py2 compat
available_zones = list(_available_zones.items())
if not get_only_available:
disabled_services = objects.ServiceList.get_all(context, disabled=True,
set_zones=True)
not_available_zones = []
azs = available_zones if not with_hosts else dict(available_zones)
zones = [(service['availability_zone'], service['host'])
for service in disabled_services
if service['availability_zone'] not in azs]
for (zone, host) in zones:
if not with_hosts and zone not in not_available_zones:
not_available_zones.append(zone)
elif with_hosts:
_not_available_zones = dict(not_available_zones)
zone_hosts = _not_available_zones.setdefault(zone, set())
zone_hosts.add(host)
# .items() returns a view in Py3, casting it to list for Py2
# compat
not_available_zones = list(_not_available_zones.items())
return (available_zones, not_available_zones)
else:
return available_zones
def get_instance_availability_zone(context, instance):
"""Return availability zone of specified instance."""
host = instance.get('host')
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 instance.az 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