OpenStack Orchestration (Heat)
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# vim: tabstop=4 shiftwidth=4 softtabstop=4
# 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
# 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.
import collections
class Attribute(object):
An attribute description and resolved value.
:param resource_name: the logical name of the resource having this
:param attr_name: the name of the attribute
:param description: attribute description
:param resolver: a function that will resolve the value of this attribute
def __init__(self, attr_name, description, resolver):
self._name = attr_name
self._description = description
self._resolve = resolver
def name(self):
:returns: The attribute name
return self._name
def value(self):
:returns: The resolved attribute value
return self._resolve(self._name)
def description(self):
:returns: A description of the attribute
return self._description
def as_output(resource_name, attr_name, description):
:param resource_name: the logical name of a resource
:param attr_name: the name of the attribute
:description: the description of the attribute
:returns: This attribute as a template 'Output' entry
return {
attr_name: {
"Value": '{"Fn::GetAtt": ["%s", "%s"]}' % (resource_name,
"Description": description
def __call__(self):
return self.value
def __str__(self):
return ("Attribute %s: %s" % (, self.value))
class Attributes(collections.Mapping):
"""Models a collection of Resource Attributes."""
def __init__(self, res_name, schema, resolver):
self._resource_name = res_name
self._attributes = dict((k, Attribute(k, v, resolver))
for k, v in schema.items())
def attributes(self):
Get a copy of the attribute definitions in this collection
(as opposed to attribute values); useful for doc and
template format generation
:returns: attribute definitions
# return a deep copy to avoid modification
return dict((k, Attribute(k, v.description, v._resolve)) for k, v
in self._attributes.items())
def as_outputs(resource_name, resource_class):
:param resource_name: logical name of the resource
:param resource_class: resource implementation class
:returns: The attributes of the specified resource_class as a template
Output map
outputs = {}
for name, descr in resource_class.attributes_schema.items():
outputs.update(Attribute.as_output(resource_name, name, descr))
return outputs
def schema_from_outputs(json_snippet):
return dict(("Outputs.%s" % k, v.get("Description"))
for k, v in json_snippet.items())
def __getitem__(self, key):
if key not in self:
raise KeyError('%s: Invalid attribute %s' %
(self._resource_name, key))
return self._attributes[key]()
def __len__(self):
return len(self._attributes)
def __contains__(self, key):
return key in self._attributes
def __iter__(self):
return iter(self._attributes)
def __repr__(self):
return ("Attributes for %s:\n\t" % self._resource_name +