Add adapters
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# Copyright 2016 Canonical Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain 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,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Adapter classes and utilities for use with Reactive interfaces"""
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from __future__ import absolute_import
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from ops.framework import Object
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class OpenStackOperRelationAdapter(object):
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"""
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Base adapter class for all OpenStack related adapters.
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"""
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interface_type = None
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"""
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The generic type of the interface the adapter is wrapping.
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"""
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def __init__(self, relation):
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"""Class will usually be initialised using the 'relation' option to
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pass in an instance of a interface class. If there is no relation
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class yet available then 'relation_name' can be used instead.
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:param relation: Instance of an interface class
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:param accessors: List of accessible interfaces properties
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:param relation_name: String name of relation
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"""
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self.relation = relation
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self._setup_properties()
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def _setup_properties(self):
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"""
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Setup property based accessors for interface.
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For charms.reactive.Endpoint interfaces a list of properties is built
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by looking for type(property) attributes added by the interface class.
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For charms.reactive.RelationBase interfaces the auto_accessors list is
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used to determine which properties to set.
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Note that the accessor is dynamic as each access calls the underlying
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getattr() for each property access.
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"""
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# Get names of properties the interface class instance has,
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# remove the properties inherited from charms.reactive.Endpoint
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# base class
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interface_instance_names = dir(self.relation)
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property_names = [
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p for p in interface_instance_names if isinstance(
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getattr(type(self.relation), p, None), property)]
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for name in property_names:
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# The double lamda trick is necessary to ensure we get fresh
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# data from the interface class property at every call to the
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# new property. Without it we would store the value that was
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# there at instantiation of this class.
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setattr(self.__class__,
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name,
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(lambda name: property(
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lambda self: getattr(
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self.relation, name)))(name))
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class ConfigurationAdapter(object):
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"""
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Configuration Adapter which provides python based access
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to all configuration options for the current charm.
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It also holds a weakref to the instance of the OpenStackCharm derived class
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that it is associated with. This is so that methods on the configuration
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adapter can query the charm class for global config (e.g. service_name).
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The configuration items from Juju are copied over and the '-' are replaced
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with '_'. This allows them to be used directly on the instance.
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"""
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def __init__(self, charm_instance):
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"""Create a ConfigurationAdapter (or derived) class.
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:param charm_instance: the instance of the OpenStackCharm derived
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class.
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"""
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for k, v in charm_instance.framework.model.config.items():
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k = k.replace('-', '_')
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setattr(self, k, v)
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class OpenStackRelationAdapters(Object):
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"""
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Base adapters class for OpenStack Charms, used to aggregate
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the relations associated with a particular charm so that their
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properties can be accessed using dot notation, e.g:
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adapters.amqp.private_address
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"""
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relation_adapters = {}
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"""
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Dictionary mapping relation names to adapter classes, e.g:
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relation_adapters = {
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'amqp': RabbitMQRelationAdapter,
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}
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By default, relations will be wrapped in an OpenStackRelationAdapter.
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Each derived class can define their OWN relation_adapters and they will
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overlay on the class further back in the class hierarchy, according to the
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mro() for the class.
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"""
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def __init__(self, relations, charm_instance, options_instance=None):
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"""
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:param relations: List of instances of relation classes
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:param options: Configuration class to use (DEPRECATED)
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:param options_instance: Instance of Configuration class to use
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:param charm_instance: optional charm_instance that is captured as a
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weakref for use on the adapter.
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"""
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self.charm_instance = charm_instance
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self._relations = set()
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self._adapters = {}
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for cls in reversed(self.__class__.mro()):
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self._adapters.update(
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{k.replace('-', '_'): v
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for k, v in getattr(cls, 'relation_adapters', {}).items()})
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self.add_relations(relations)
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setattr(self, 'options', ConfigurationAdapter(charm_instance))
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def __iter__(self):
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"""
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Iterate over the relations presented to the charm.
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"""
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for relation in self._relations:
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yield relation, getattr(self, relation)
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def add_relations(self, relations):
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"""Add the relations to this adapters instance for use as a context.
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:params relations: list of RAW reactive relation instances.
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"""
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for relation in relations:
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self.add_relation(relation)
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def add_relation(self, relation):
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"""Add the relation to this adapters instance for use as a context.
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:param relation: a RAW reactive relation instance
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"""
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adapter_name, adapter = self.make_adapter(relation)
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setattr(self, adapter_name, adapter)
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self._relations.add(adapter_name)
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def make_adapter(self, relation):
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"""Make an adapter from a reactive relation.
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This returns the relation_name and the adapter instance based on the
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registered custom adapter classes and any customised properties on
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those adapter classes.
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:param relation: a RelationBase derived reactive relation
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:returns (string, OpenstackRelationAdapter-derived): see above.
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"""
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try:
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relation_name = relation.endpoint_name.replace('-', '_')
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except AttributeError:
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relation_name = relation.relation_name.replace('-', '_')
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try:
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adapter = self._adapters[relation_name](relation)
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except KeyError:
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adapter = OpenStackOperRelationAdapter(relation)
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return relation_name, adapter
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