e11ecb4f43
The documentation says that the 'Fn::Base64' function converts an input string into Base64, while the implementation is actually a pass-through. This patch fixes the documentation to avoid confusions caused to users. Change-Id: I643e73f7ed258da06d09f17a3302a258e3303414 Closes-Bug: 1377323
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6.4 KiB
ReStructuredText
332 lines
6.4 KiB
ReStructuredText
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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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http://www.apache.org/licenses/LICENSE-2.0
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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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===================================
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CloudFormation Compatible Functions
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===================================
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There are a number of functions that you can use to help you write
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CloudFormation compatible templates. While most CloudFormation functions are
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supported in HOT version '2013-05-23', *Fn::Select* is the only CloudFormation
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function supported in HOT templates since version '2014-10-16' which is
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introduced in Juno.
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All of these functions (except *Ref*) start with *Fn::*.
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---
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Ref
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---
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Returns the value of the named parameter or resource.
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Parameters
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~~~~~~~~~~
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name : String
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The name of the resource or parameter.
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Usage
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~~~~~
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::
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{Ref: my_server}
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Returns the nova instance ID. For example, ``d8093de0-850f-4513-b202-7979de6c0d55``.
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----------
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Fn::Base64
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----------
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This is a placeholder for a function to convert an input string to Base64.
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This function in Heat actually performs no conversion. It is included for
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the benefit of CFN templates that convert UserData to Base64. Heat only
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accepts UserData in plain text.
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Parameters
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~~~~~~~~~~
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value : String
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The string to convert.
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Usage
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~~~~~
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::
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{"Fn::Base64": "convert this string please."}
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Returns the original input string.
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-------------
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Fn::FindInMap
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-------------
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Returns the value corresponding to keys into a two-level map declared in the
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Mappings section.
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Parameters
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~~~~~~~~~~
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map_name : String
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The logical name of a mapping declared in the Mappings section that
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contains the keys and values.
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top_level_key : String
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The top-level key name. It's value is a list of key-value pairs.
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second_level_key : String
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The second-level key name, which is set to one of the keys from the list
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assigned to top_level_key.
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Usage
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~~~~~
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::
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Mapping:
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MyContacts:
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jone: {phone: 337, email: a@b.com}
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jim: {phone: 908, email: g@b.com}
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{"Fn::FindInMap": ["MyContacts", "jim", "phone" ] }
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Returns ``908``.
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----------
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Fn::GetAtt
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----------
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Returns an attribute of a resource within the template.
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Parameters
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~~~~~~~~~~
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resource : String
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The name of the resource.
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attribute : String
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The name of the attribute.
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Usage
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~~~~~
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::
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{Fn::GetAtt: [my_server, PublicIp]}
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Returns an IP address such as ``10.0.0.2``.
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----------
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Fn::GetAZs
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----------
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Returns the Availability Zones within the given region.
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*Note: AZ's and regions are not fully implemented in Heat.*
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Parameters
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~~~~~~~~~~
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region : String
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The name of the region.
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Usage
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~~~~~
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::
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{Fn::GetAZs: ""}
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Returns the list provided by ``nova availability-zone-list``.
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--------
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Fn::Join
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--------
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Like python join, it joins a list of strings with the given delimiter.
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Parameters
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~~~~~~~~~~
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delimiter : String
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The string to join the list with.
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list : list
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The list to join.
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Usage
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~~~~~
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::
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{Fn::Join: [",", ["beer", "wine", "more beer"]]}
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Returns ``beer, wine, more beer``.
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----------
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Fn::Select
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----------
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Select an item from a list.
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*Heat extension: Select an item from a map*
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Parameters
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~~~~~~~~~~
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selector : string or integer
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The number of item in the list or the name of the item in the map.
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collection : map or list
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The collection to select the item from.
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Usage
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~~~~~
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For a list lookup:
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::
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{ "Fn::Select" : [ "2", [ "apples", "grapes", "mangoes" ] ] }
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Returns ``mangoes``.
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For a map lookup:
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::
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{ "Fn::Select" : [ "red", {"red": "a", "flu": "b"} ] }
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Returns ``a``.
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---------
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Fn::Split
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---------
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This is the reverse of Join. Convert a string into a list based on the
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delimiter.
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Parameters
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~~~~~~~~~~
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delimiter : string
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Matching string to split on.
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string : String
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The string to split.
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Usage
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~~~~~
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::
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{ "Fn::Split" : [ ",", "str1,str2,str3,str4"]}
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Returns ``{["str1", "str2", "str3", "str4"]}``.
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-----------
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Fn::Replace
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-----------
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Find and replace one string with another.
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Parameters
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~~~~~~~~~~
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substitutions : map
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A map of substitutions.
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string: String
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The string to do the substitutions in.
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Usage
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~~~~~
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::
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{"Fn::Replace": [
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{'$var1': 'foo', '%var2%': 'bar'},
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'$var1 is %var2%'
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]}
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Returns ``"foo is bar"``.
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------------------
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Fn::ResourceFacade
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------------------
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When writing a Template Resource:
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- user writes a template that will fill in for a resource (the resource is the facade).
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- when they are writing their template they need to access the metadata from
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the facade.
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Parameters
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~~~~~~~~~~
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attribute_name : String
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One of ``Metadata``, ``DeletionPolicy`` or ``UpdatePolicy``.
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Usage
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~~~~~
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::
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{'Fn::ResourceFacade': 'Metadata'}
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{'Fn::ResourceFacade': 'DeletionPolicy'}
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{'Fn::ResourceFacade': 'UpdatePolicy'}
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Example
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~~~~~~~
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Here is a top level template ``top.yaml``
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::
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resources:
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my_server:
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type: OS::Nova::Server
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metadata:
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key: value
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some: more stuff
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Here is a resource template ``my_actual_server.yaml``
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::
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resources:
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_actual_server_:
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type: OS::Nova::Server
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metadata: {'Fn::ResourceFacade': Metadata}
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The environment file ``env.yaml``
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::
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resource_registry:
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resources:
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my_server:
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"OS::Nova::Server": my_actual_server.yaml
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To use it
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::
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$ heat stack-create -f top.yaml -e env.yaml
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What happened is the metadata in ``top.yaml`` (key: value, some: more
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stuff) gets passed into the resource template via the `Fn::ResourceFacade`_
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function.
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-------------------
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Fn::MemberListToMap
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-------------------
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Convert an AWS style member list into a map.
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Parameters
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~~~~~~~~~~
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key name: string
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The name of the key (normally "Name" or "Key").
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value name: string
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The name of the value (normally "Value").
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list: A list of strings
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The string to convert.
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Usage
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~~~~~
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::
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{'Fn::MemberListToMap': ['Name', 'Value', ['.member.0.Name=key',
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'.member.0.Value=door',
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'.member.1.Name=colour',
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'.member.1.Value=green']]}
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Returns ``{'key': 'door', 'colour': 'green'}``.
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