3be95adceb
In order for projects to use the namespace property of Targets in a backwards compatible way (To support rolling upgrades), a Target may now belong to more than a single namespace (i.e. 'namespace1' and None). This way, if the server is upgraded first, the version that introduces namespaces to a project will place the server RPC methods in ['some_namespace', None]. Pre-upgrade agents will send messages in the null namespace while post-upgrade agents will send messages in 'some_namespace', and both will be accepted. Change-Id: I713fe9228111c36aa3f7fb95cbd59c99100e8c96 Closes-Bug: #1430984
102 lines
4.0 KiB
Python
102 lines
4.0 KiB
Python
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# Copyright 2013 Red Hat, Inc.
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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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class Target(object):
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"""Identifies the destination of messages.
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A Target encapsulates all the information to identify where a message
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should be sent or what messages a server is listening for.
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Different subsets of the information encapsulated in a Target object is
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relevant to various aspects of the API:
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creating a server:
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topic and server is required; exchange is optional
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an endpoint's target:
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namespace and version is optional
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client sending a message:
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topic is required, all other attributes optional
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Its attributes are:
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:param exchange: A scope for topics. Leave unspecified to default to the
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control_exchange configuration option.
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:type exchange: str
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:param topic: A name which identifies the set of interfaces exposed by a
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server. Multiple servers may listen on a topic and messages will be
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dispatched to one of the servers in a round-robin fashion.
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:type topic: str
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:param namespace: Identifies a particular interface (i.e. set of methods)
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exposed by a server. The default interface has no namespace identifier
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and is referred to as the null namespace.
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:type namespace: str
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:param version: Interfaces have a major.minor version number associated
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with them. A minor number increment indicates a backwards compatible
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change and an incompatible change is indicated by a major number bump.
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Servers may implement multiple major versions and clients may require
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indicate that their message requires a particular minimum minor version.
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:type version: str
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:param server: Clients can request that a message be directed to a specific
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server, rather than just one of a pool of servers listening on the topic.
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:type server: str
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:param fanout: Clients may request that a message be directed to all
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servers listening on a topic by setting fanout to ``True``, rather than
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just one of them.
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:type fanout: bool
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:param legacy_namespaces: A server always accepts messages specified via
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the 'namespace' parameter, and may also accept messages defined via
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this parameter. This option should be used to switch namespaces safely
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during rolling upgrades.
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:type legacy_namespaces: list of strings
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"""
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def __init__(self, exchange=None, topic=None, namespace=None,
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version=None, server=None, fanout=None,
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legacy_namespaces=None):
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self.exchange = exchange
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self.topic = topic
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self.namespace = namespace
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self.version = version
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self.server = server
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self.fanout = fanout
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self.accepted_namespaces = [namespace] + (legacy_namespaces or [])
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def __call__(self, **kwargs):
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for a in ('exchange', 'topic', 'namespace',
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'version', 'server', 'fanout'):
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kwargs.setdefault(a, getattr(self, a))
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return Target(**kwargs)
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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 ['exchange', 'topic', 'namespace',
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'version', 'server', 'fanout']:
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v = getattr(self, a)
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if v:
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attrs.append((a, v))
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values = ', '.join(['%s=%s' % i for i in attrs])
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return '<Target ' + values + '>'
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def __hash__(self):
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return id(self)
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