316 lines
11 KiB
Python
316 lines
11 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""Multicast DNS implementation for API discovery.
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This implementation follows RFC 6763 as clarified by the API SIG guideline
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https://review.opendev.org/651222.
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"""
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import collections
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import ipaddress
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import socket
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import time
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from urllib import parse as urlparse
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from oslo_config import cfg
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from oslo_config import types as cfg_types
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from oslo_log import log as logging
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import zeroconf
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from ironic_lib.common.i18n import _
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from ironic_lib import exception
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from ironic_lib import utils
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opts = [
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cfg.IntOpt('registration_attempts',
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min=1, default=5,
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help='Number of attempts to register a service. Currently '
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'has to be larger than 1 because of race conditions '
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'in the zeroconf library.'),
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cfg.IntOpt('lookup_attempts',
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min=1, default=3,
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help='Number of attempts to lookup a service.'),
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cfg.Opt('params',
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# This is required for values that contain commas.
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type=cfg_types.Dict(cfg_types.String(quotes=True)),
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default={},
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help='Additional parameters to pass for the registered '
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'service.'),
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cfg.ListOpt('interfaces',
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help='List of IP addresses of interfaces to use for mDNS. '
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'Defaults to all interfaces on the system.'),
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]
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CONF = cfg.CONF
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opt_group = cfg.OptGroup(name='mdns', title='Options for multicast DNS')
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CONF.register_group(opt_group)
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CONF.register_opts(opts, opt_group)
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LOG = logging.getLogger(__name__)
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_MDNS_DOMAIN = '_openstack._tcp.local.'
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_endpoint = collections.namedtuple('Endpoint',
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['addresses', 'hostname', 'port', 'params'])
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class Zeroconf(object):
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"""Multicast DNS implementation client and server.
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Uses threading internally, so there is no start method. It starts
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automatically on creation.
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.. warning::
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The underlying library does not yet support IPv6.
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"""
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def __init__(self):
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"""Initialize and start the mDNS server."""
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interfaces = (CONF.mdns.interfaces if CONF.mdns.interfaces
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else zeroconf.InterfaceChoice.All)
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self._zc = zeroconf.Zeroconf(interfaces=interfaces)
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self._registered = []
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def register_service(self, service_type, endpoint, params=None):
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"""Register a service.
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This call announces the new services via multicast and instructs the
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built-in server to respond to queries about it.
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:param service_type: OpenStack service type, e.g. "baremetal".
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:param endpoint: full endpoint to reach the service.
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:param params: optional properties as a dictionary.
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:raises: :exc:`.ServiceRegistrationFailure` if the service cannot be
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registered, e.g. because of conflicts.
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"""
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parsed = _parse_endpoint(endpoint, service_type)
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all_params = CONF.mdns.params.copy()
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if params:
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all_params.update(params)
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all_params.update(parsed.params)
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# TODO(dtantsur): allow overriding TTL values via configuration
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info = zeroconf.ServiceInfo(_MDNS_DOMAIN,
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'%s.%s' % (service_type, _MDNS_DOMAIN),
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addresses=parsed.addresses,
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port=parsed.port,
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properties=all_params,
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server=parsed.hostname)
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LOG.debug('Registering %s via mDNS', info)
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# Work around a potential race condition in the registration code:
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# https://github.com/jstasiak/python-zeroconf/issues/163
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delay = 0.1
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try:
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for attempt in range(CONF.mdns.registration_attempts):
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try:
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self._zc.register_service(info)
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except zeroconf.NonUniqueNameException:
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LOG.debug('Could not register %s - conflict', info)
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if attempt == CONF.mdns.registration_attempts - 1:
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raise
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# reset the cache to purge learned records and retry
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self._zc.cache = zeroconf.DNSCache()
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time.sleep(delay)
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delay *= 2
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else:
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break
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except zeroconf.Error as exc:
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raise exception.ServiceRegistrationFailure(
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service=service_type, error=exc)
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self._registered.append(info)
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def get_endpoint(self, service_type, skip_loopback=True,
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skip_link_local=False):
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"""Get an endpoint and its properties from mDNS.
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If the requested endpoint is already in the built-in server cache, and
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its TTL is not exceeded, the cached value is returned.
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:param service_type: OpenStack service type.
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:param skip_loopback: Whether to ignore loopback addresses.
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:param skip_link_local: Whether to ignore link local V6 addresses.
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:returns: tuple (endpoint URL, properties as a dict).
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:raises: :exc:`.ServiceLookupFailure` if the service cannot be found.
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"""
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delay = 0.1
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for attempt in range(CONF.mdns.lookup_attempts):
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name = '%s.%s' % (service_type, _MDNS_DOMAIN)
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info = self._zc.get_service_info(name, name)
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if info is not None:
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break
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elif attempt == CONF.mdns.lookup_attempts - 1:
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raise exception.ServiceLookupFailure(service=service_type)
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else:
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time.sleep(delay)
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delay *= 2
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all_addr = info.parsed_addresses()
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# Try to find the first routable address
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for addr in all_addr:
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try:
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loopback = ipaddress.ip_address(addr).is_loopback
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except ValueError:
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LOG.debug('Skipping invalid IP address %s', addr)
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continue
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else:
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if loopback and skip_loopback:
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LOG.debug('Skipping loopback IP address %s', addr)
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continue
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if utils.get_route_source(addr, skip_link_local):
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address = addr
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break
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else:
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LOG.warning('None of addresses %s seem routable, using '
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'the first one', all_addr)
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address = all_addr[0]
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properties = {}
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for key, value in info.properties.items():
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try:
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if isinstance(key, bytes):
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key = key.decode('utf-8')
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except UnicodeError as exc:
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raise exception.ServiceLookupFailure(
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_('Invalid properties for service %(svc)s. Cannot decode '
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'key %(key)r: %(exc)r') %
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{'svc': service_type, 'key': key, 'exc': exc})
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try:
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if isinstance(value, bytes):
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value = value.decode('utf-8')
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except UnicodeError as exc:
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LOG.debug('Cannot convert value %(value)r for key %(key)s '
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'to string, assuming binary: %(exc)s',
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{'key': key, 'value': value, 'exc': exc})
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properties[key] = value
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path = properties.pop('path', '')
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protocol = properties.pop('protocol', None)
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if not protocol:
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if info.port == 80:
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protocol = 'http'
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else:
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protocol = 'https'
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if info.server.endswith('.local.'):
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# Local hostname means that the catalog lists an IP address,
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# so use it
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host = address
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if int(ipaddress.ip_address(host).version) == 6:
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host = '[%s]' % host
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else:
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# Otherwise use the provided hostname.
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host = info.server.rstrip('.')
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return ('{proto}://{host}:{port}{path}'.format(proto=protocol,
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host=host,
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port=info.port,
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path=path),
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properties)
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def close(self):
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"""Shut down mDNS and unregister services.
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.. note::
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If another server is running for the same services, it will
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re-register them immediately.
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"""
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for info in self._registered:
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try:
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self._zc.unregister_service(info)
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except Exception:
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LOG.exception('Cound not unregister mDNS service %s', info)
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self._zc.close()
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def __enter__(self):
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return self
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def __exit__(self, *args):
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self.close()
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def get_endpoint(service_type):
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"""Get an endpoint and its properties from mDNS.
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If the requested endpoint is already in the built-in server cache, and
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its TTL is not exceeded, the cached value is returned.
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:param service_type: OpenStack service type.
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:returns: tuple (endpoint URL, properties as a dict).
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:raises: :exc:`.ServiceLookupFailure` if the service cannot be found.
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"""
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with Zeroconf() as zc:
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return zc.get_endpoint(service_type)
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def _parse_endpoint(endpoint, service_type=None):
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params = {}
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url = urlparse.urlparse(endpoint)
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port = url.port
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if port is None:
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if url.scheme == 'https':
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port = 443
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else:
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port = 80
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addresses = []
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hostname = url.hostname
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try:
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infos = socket.getaddrinfo(hostname, port, 0, socket.IPPROTO_TCP)
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except socket.error as exc:
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raise exception.ServiceRegistrationFailure(
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service=service_type,
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error=_('Could not resolve hostname %(host)s: %(exc)s') %
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{'host': hostname, 'exc': exc})
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for info in infos:
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ip = info[4][0]
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if ip == hostname:
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# we need a host name for the service record. if what we have in
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# the catalog is an IP address, use the local hostname instead
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hostname = None
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# zeroconf requires addresses in network format
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ip = socket.inet_pton(info[0], ip)
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if ip not in addresses:
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addresses.append(ip)
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if not addresses:
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raise exception.ServiceRegistrationFailure(
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service=service_type,
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error=_('No suitable addresses found for %s') % url.hostname)
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# avoid storing information that can be derived from existing data
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if url.path not in ('', '/'):
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params['path'] = url.path
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if (not (port == 80 and url.scheme == 'http')
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and not (port == 443 and url.scheme == 'https')):
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params['protocol'] = url.scheme
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# zeroconf is pretty picky about having the trailing dot
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if hostname is not None and not hostname.endswith('.'):
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hostname += '.'
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return _endpoint(addresses, hostname, port, params)
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def list_opts():
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"""Entry point for oslo-config-generator."""
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return [('mdns', opts)]
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