c846cf35b8
Nova's cells/rpc_driver.py has some code which allows user of the REST
API to update elements of a cell's transport URL (say, the host name of
the message broker) stored in the database. To achieve this, it has
a parse_transport_url() method which breaks the URL into its constituent
parts and an unparse_transport_url() which re-forms it again after
updating some of its parts.
This is all fine and, since it's fairly specialized, it wouldn't be a
big deal to leave this code in Nova for now ... except the unparse
method looks at CONF.rpc_backend to know what scheme to use in the
returned URL if now backend was specified.
oslo.messaging registers the rpc_backend option, but the ability to
reference any option registered by the library should not be relied upon
by users of the library. Imagine, for instance, if we renamed the option
in future (with backwards compat for old configurations), then this
would mean API breakage.
So, long story short - an API along these lines makes some sense, but
especially since not having it would mean we'd need to add some way to
query the name of the transport driver.
In this commit, we add a simple new TransportURL class:
>>> url = messaging.TransportURL.parse(cfg.CONF, 'foo:///')
>>> str(url), url
('foo:///', <TransportURL transport='foo'>)
>>> url.hosts.append(messaging.TransportHost(hostname='localhost'))
>>> str(url), url
('foo://localhost/', <TransportURL transport='foo', hosts=[<TransportHost hostname='localhost'>]>)
>>> url.transport = None
>>> str(url), url
('kombu://localhost/', <TransportURL transport='kombu', hosts=[<TransportHost hostname='localhost'>]>)
>>> cfg.CONF.set_override('rpc_backend', 'bar')
>>> str(url), url
('bar://localhost/', <TransportURL transport='bar', hosts=[<TransportHost hostname='localhost'>]>)
The TransportURL.parse() method equates to parse_transport_url() and
TransportURL.__str__() equates to unparse_transport().
The transport drivers are also updated to take a TransportURL as a
required argument, which simplifies the handling of transport URLs in
the drivers.
Change-Id: Ic04173476329858e4a2c2d2707e9d4aeb212d127
398 lines
13 KiB
Python
398 lines
13 KiB
Python
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# Copyright 2010 United States Government as represented by the
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# Administrator of the National Aeronautics and Space Administration.
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# All Rights Reserved.
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# Copyright 2013 Red Hat, Inc.
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# Copyright (c) 2012 Rackspace Hosting
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#
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# 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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__all__ = [
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'DriverLoadFailure',
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'InvalidTransportURL',
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'Transport',
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'TransportHost',
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'TransportURL',
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'get_transport',
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'set_transport_defaults',
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]
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import urllib
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import urlparse
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from oslo.config import cfg
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from stevedore import driver
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from oslo.messaging import exceptions
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_transport_opts = [
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cfg.StrOpt('transport_url',
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default=None,
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help='A URL representing the messaging driver to use and its '
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'full configuration. If not set, we fall back to the '
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'rpc_backend option and driver specific configuration.'),
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cfg.StrOpt('rpc_backend',
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default='kombu',
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help='The messaging driver to use, defaults to kombu. Other '
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'drivers include qpid and zmq.'),
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cfg.StrOpt('control_exchange',
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default='openstack',
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help='The default exchange under which topics are scoped. May '
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'be overridden by an exchange name specified in the '
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'transport_url option.'),
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]
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def set_transport_defaults(control_exchange):
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"""Set defaults for messaging transport configuration options.
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:param control_exchange: the default exchange under which topics are scoped
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:type control_exchange: str
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"""
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cfg.set_defaults(_transport_opts,
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control_exchange=control_exchange)
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class Transport(object):
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"""A messaging transport.
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This is a mostly opaque handle for an underlying messaging transport
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driver.
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It has a single 'conf' property which is the cfg.ConfigOpts instance used
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to construct the transport object.
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"""
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def __init__(self, driver):
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self.conf = driver.conf
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self._driver = driver
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def _send(self, target, ctxt, message, wait_for_reply=None, timeout=None):
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if not target.topic:
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raise exceptions.InvalidTarget('A topic is required to send',
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target)
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return self._driver.send(target, ctxt, message,
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wait_for_reply=wait_for_reply,
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timeout=timeout)
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def _send_notification(self, target, ctxt, message, version):
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if not target.topic:
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raise exceptions.InvalidTarget('A topic is required to send',
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target)
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self._driver.send(target, ctxt, message, version)
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def _listen(self, target):
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if not (target.topic and target.server):
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raise exceptions.InvalidTarget('A server\'s target must have '
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'topic and server names specified',
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target)
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return self._driver.listen(target)
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def cleanup(self):
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"""Release all resources associated with this transport."""
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self._driver.cleanup()
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class InvalidTransportURL(exceptions.MessagingException):
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"""Raised if transport URL is invalid."""
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def __init__(self, url, msg):
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super(InvalidTransportURL, self).__init__(msg)
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self.url = url
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class DriverLoadFailure(exceptions.MessagingException):
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"""Raised if a transport driver can't be loaded."""
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def __init__(self, driver, ex):
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msg = 'Failed to load transport driver "%s": %s' % (driver, ex)
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super(DriverLoadFailure, self).__init__(msg)
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self.driver = driver
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self.ex = ex
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def get_transport(conf, url=None, allowed_remote_exmods=[]):
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"""A factory method for Transport objects.
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This method will construct a Transport object from transport configuration
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gleaned from the user's configuration and, optionally, a transport URL.
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If a transport URL is supplied as a parameter, any transport configuration
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contained in it takes precedence. If no transport URL is supplied, but
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there is a transport URL supplied in the user's configuration then that
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URL will take the place of the url parameter. In both cases, any
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configuration not supplied in the transport URL may be taken from
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individual configuration parameters in the user's configuration.
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An example transport URL might be::
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rabbit://me:passwd@host:5672/virtual_host
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and can either be passed as a string or a TransportURL object.
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:param conf: the user configuration
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:type conf: cfg.ConfigOpts
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:param url: a transport URL
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:type url: str or TransportURL
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:param allowed_remote_exmods: a list of modules which a client using this
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transport will deserialize remote exceptions
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from
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:type allowed_remote_exmods: list
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"""
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conf.register_opts(_transport_opts)
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if not isinstance(url, TransportURL):
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url = url or conf.transport_url
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parsed = TransportURL.parse(conf, url)
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if not parsed.transport:
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raise InvalidTransportURL(url, 'No scheme specified in "%s"' % url)
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url = parsed
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kwargs = dict(default_exchange=conf.control_exchange,
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allowed_remote_exmods=allowed_remote_exmods)
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try:
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mgr = driver.DriverManager('oslo.messaging.drivers',
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url.transport,
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invoke_on_load=True,
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invoke_args=[conf, url],
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invoke_kwds=kwargs)
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except RuntimeError as ex:
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raise DriverLoadFailure(url.transport, ex)
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return Transport(mgr.driver)
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class TransportHost(object):
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"""A host element of a parsed transport URL."""
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def __init__(self, hostname=None, port=None, username=None, password=None):
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self.hostname = hostname
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self.port = port
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self.username = username
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self.password = password
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def __eq__(self, other):
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return vars(self) == vars(other)
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def __ne__(self, other):
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return not self == other
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def __repr__(self):
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attrs = []
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for a in ['hostname', 'port', 'username', 'password']:
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v = getattr(self, a)
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if v:
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attrs.append((a, repr(v)))
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values = ', '.join(['%s=%s' % i for i in attrs])
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return '<TransportHost ' + values + '>'
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class TransportURL(object):
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"""A parsed transport URL.
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Transport URLs take the form::
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transport://user:pass@host1:port[,hostN:portN]/virtual_host
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i.e. the scheme selects the transport driver, you may include multiple
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hosts in netloc and the path part is a "virtual host" partition path.
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:param conf: a ConfigOpts instance
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:type conf: oslo.config.cfg.ConfigOpts
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:param transport: a transport name e.g. 'rabbit' or 'qpid'
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:type transport: str
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:param virtual_host: a virtual host path e.g. '/'
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:type virtual_host: str
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:param hosts: a list of TransportHost objects
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:type hosts: list
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"""
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def __init__(self, conf, transport=None, virtual_host=None, hosts=None):
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self.conf = conf
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self.conf.register_opts(_transport_opts)
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self._transport = transport
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self._virtual_host = virtual_host
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self._hosts = hosts
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if self._hosts is None:
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self._hosts = []
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@property
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def transport(self):
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if self._transport is None:
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return self.conf.rpc_backend
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else:
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return self._transport
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@transport.setter
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def transport(self, value):
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self._transport = value
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@property
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def virtual_host(self):
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return self._virtual_host
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@virtual_host.setter
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def virtual_host(self, value):
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self._virtual_host = value
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@property
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def hosts(self):
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return self._hosts
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def __eq__(self, other):
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return (self.transport == other.transport and
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self.virtual_host == other.virtual_host and
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self.hosts == other.hosts)
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def __ne__(self, other):
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return not self == other
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def __repr__(self):
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attrs = []
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for a in ['transport', 'virtual_host', 'hosts']:
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v = getattr(self, a)
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if v:
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attrs.append((a, repr(v)))
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values = ', '.join(['%s=%s' % i for i in attrs])
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return '<TransportURL ' + values + '>'
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def __str__(self):
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netlocs = []
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for host in self.hosts:
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username = host.username
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password = host.password
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hostname = host.hostname
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port = host.port
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# Starting place for the network location
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netloc = ''
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# Build the username and password portion of the transport URL
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if username is not None or password is not None:
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if username is not None:
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netloc += urllib.quote(username, '')
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if password is not None:
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netloc += ':%s' % urllib.quote(password, '')
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netloc += '@'
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# Build the network location portion of the transport URL
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if hostname:
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if ':' in hostname:
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netloc += '[%s]' % hostname
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else:
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netloc += hostname
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if port is not None:
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netloc += ':%d' % port
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netlocs.append(netloc)
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# Assemble the transport URL
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url = '%s://%s/' % (self.transport, ','.join(netlocs))
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if self.virtual_host:
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url += urllib.quote(self.virtual_host)
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return url
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@classmethod
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def parse(cls, conf, url):
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"""Parse an url.
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Assuming a URL takes the form of:
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transport://user:pass@host1:port[,hostN:portN]/virtual_host
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then parse the URL and return a TransportURL object.
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Netloc is parsed following the sequence bellow:
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* It is first splitted by ',' in order to support multiple hosts
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* The last parsed username and password will be propagated to the rest
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of hotsts specified:
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user:passwd@host1:port1,host2:port2
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[
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{"username": "user", "password": "passwd", "host": "host1:port1"},
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{"username": "user", "password": "passwd", "host": "host2:port2"}
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]
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* In order to avoid the above propagation, it is possible to alter the
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order in which the hosts are specified or specify a set of fake
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credentials using ",:@host2:port2"
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user:passwd@host1:port1,:@host2:port2
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[
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{"username": "user", "password": "passwd", "host": "host1:port1"},
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{"username": "", "password": "", "host": "host2:port2"}
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]
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:param conf: a ConfigOpts instance
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:type conf: oslo.config.cfg.ConfigOpts
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:param url: The URL to parse
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:type url: str
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:returns: A TransportURL
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"""
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if not url:
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return cls(conf)
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# FIXME(flaper87): Not PY3K compliant
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if not isinstance(url, basestring):
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raise InvalidTransportURL(url, 'Wrong URL type')
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url = urlparse.urlparse(url)
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# Make sure there's not a query string; that could identify
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# requirements we can't comply with (e.g., ssl), so reject it if
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# it's present
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if '?' in url.path or url.query:
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raise InvalidTransportURL(url.geturl(),
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"Cannot comply with query string in "
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"transport URL")
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virtual_host = None
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if url.path.startswith('/'):
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virtual_host = url.path[1:]
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hosts = []
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username = password = ''
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for host in url.netloc.split(','):
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if not host:
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continue
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hostname = host
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username = password = port = None
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if '@' in host:
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username, hostname = host.split('@', 1)
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if ':' in username:
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username, password = username.split(':', 1)
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if ':' in hostname:
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hostname, port = hostname.split(':', 1)
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port = int(port)
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hosts.append(TransportHost(hostname=hostname,
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port=port,
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username=username,
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password=password))
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return cls(conf, url.scheme, virtual_host, hosts)
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