openstack-manuals/doc/hot-reference/generated/functions.xml

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<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xi="http://www.w3.org/2001/XInclude" xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0" xml:id="cloudformation-compatible-functions">
  <!--WARNING: This file is automatically generated. Do not edit it.-->
  <title>CloudFormation Compatible Functions</title>
  <para>There are a number of functions that you can use to help you write
CloudFormation compatible templates.  While most CloudFormation functions are
supported in HOT version '2013-05-23', <emphasis>Fn::Select</emphasis> is the only CloudFormation
function supported in HOT templates since version '2014-10-16' which is
introduced in Juno.</para>
  <para>All of these functions (except <emphasis>Ref</emphasis>) start with <emphasis>Fn::</emphasis>.</para>
  <section xml:id="ref">
    <?dbhtml stop-chunking?>
    <title>Ref</title>
    <para>Returns the value of the named parameter or resource.</para>
    <section xml:id="parameters">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="String">name</term>
          <listitem>
            <para>The name of the resource or parameter.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="usage">
      <title>Usage</title>
      <programlisting>{Ref: my_server}</programlisting>
      <para>Returns the nova instance ID. For example, <literal>d8093de0-850f-4513-b202-7979de6c0d55</literal>.</para>
    </section>
  </section>
  <section xml:id="fn-base64">
    <?dbhtml stop-chunking?>
    <title>Fn::Base64</title>
    <para>This is a placeholder for a function to convert an input string to Base64.
This function in Heat actually performs no conversion.  It is included for
the benefit of CFN templates that convert UserData to Base64.  Heat only
accepts UserData in plain text.</para>
    <section xml:id="id1">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="String">value</term>
          <listitem>
            <para>The string to convert.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id2">
      <title>Usage</title>
      <programlisting>{"Fn::Base64": "convert this string please."}</programlisting>
      <para>Returns the original input string.</para>
    </section>
  </section>
  <section xml:id="fn-findinmap">
    <?dbhtml stop-chunking?>
    <title>Fn::FindInMap</title>
    <para>Returns the value corresponding to keys into a two-level map declared in the
Mappings section.</para>
    <section xml:id="id3">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="String">map_name</term>
          <listitem>
            <para>The logical name of a mapping declared in the Mappings section that
contains the keys and values.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term role="String">top_level_key</term>
          <listitem>
            <para>The top-level key name. It's value is a list of key-value pairs.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term role="String">second_level_key</term>
          <listitem>
            <para>The second-level key name, which is set to one of the keys from the list
assigned to top_level_key.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id4">
      <title>Usage</title>
      <programlisting>Mapping:
  MyContacts:
    jone: {phone: 337, email: a@b.com}
    jim: {phone: 908, email: g@b.com}

{"Fn::FindInMap": ["MyContacts", "jim", "phone" ] }</programlisting>
      <para>Returns <literal>908</literal>.</para>
    </section>
  </section>
  <section xml:id="fn-getatt">
    <?dbhtml stop-chunking?>
    <title>Fn::GetAtt</title>
    <para>Returns an attribute of a resource within the template.</para>
    <section xml:id="id5">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="String">resource</term>
          <listitem>
            <para>The name of the resource.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term role="String">attribute</term>
          <listitem>
            <para>The name of the attribute.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id6">
      <title>Usage</title>
      <programlisting>{Fn::GetAtt: [my_server, PublicIp]}</programlisting>
      <para>Returns an IP address such as <literal>10.0.0.2</literal>.</para>
    </section>
  </section>
  <section xml:id="fn-getazs">
    <?dbhtml stop-chunking?>
    <title>Fn::GetAZs</title>
    <para>Returns the Availability Zones within the given region.</para>
    <para>
      <emphasis>Note: AZ's and regions are not fully implemented in Heat.</emphasis>
    </para>
    <section xml:id="id7">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="String">region</term>
          <listitem>
            <para>The name of the region.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id8">
      <title>Usage</title>
      <programlisting>{Fn::GetAZs: ""}</programlisting>
      <para>Returns the list provided by <literal>nova availability-zone-list</literal>.</para>
    </section>
  </section>
  <section xml:id="fn-join">
    <?dbhtml stop-chunking?>
    <title>Fn::Join</title>
    <para>Like python join, it joins a list of strings with the given delimiter.</para>
    <section xml:id="id9">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="String">delimiter</term>
          <listitem>
            <para>The string to join the list with.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term role="list">list</term>
          <listitem>
            <para>The list to join.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id10">
      <title>Usage</title>
      <programlisting>{Fn::Join: [",", ["beer", "wine", "more beer"]]}</programlisting>
      <para>Returns <literal>beer, wine, more beer</literal>.</para>
    </section>
  </section>
  <section xml:id="fn-select">
    <?dbhtml stop-chunking?>
    <title>Fn::Select</title>
    <para>Select an item from a list.</para>
    <para>
      <emphasis>Heat extension: Select an item from a map</emphasis>
    </para>
    <section xml:id="id11">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="string or integer">selector</term>
          <listitem>
            <para>The number of item in the list or the name of the item in the map.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term role="map or list">collection</term>
          <listitem>
            <para>The collection to select the item from.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id12">
      <title>Usage</title>
      <para>For a list lookup:</para>
      <programlisting>{ "Fn::Select" : [ "2", [ "apples", "grapes", "mangoes" ] ] }</programlisting>
      <para>Returns <literal>mangoes</literal>.</para>
      <para>For a map lookup:</para>
      <programlisting>{ "Fn::Select" : [ "red", {"red": "a", "flu": "b"} ] }</programlisting>
      <para>Returns <literal>a</literal>.</para>
    </section>
  </section>
  <section xml:id="fn-split">
    <?dbhtml stop-chunking?>
    <title>Fn::Split</title>
    <para>This is the reverse of Join. Convert a string into a list based on the
delimiter.</para>
    <section xml:id="id13">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="string">delimiter</term>
          <listitem>
            <para>Matching string to split on.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term role="String">string</term>
          <listitem>
            <para>The string to split.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id14">
      <title>Usage</title>
      <programlisting>{ "Fn::Split" : [ ",", "str1,str2,str3,str4"]}</programlisting>
      <para>Returns <literal>{["str1", "str2", "str3", "str4"]}</literal>.</para>
    </section>
  </section>
  <section xml:id="fn-replace">
    <?dbhtml stop-chunking?>
    <title>Fn::Replace</title>
    <para>Find and replace one string with another.</para>
    <section xml:id="id15">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="map">substitutions</term>
          <listitem>
            <para>A map of substitutions.</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>string: String</term>
          <listitem>
            <para>The string to do the substitutions in.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id16">
      <title>Usage</title>
      <programlisting>{"Fn::Replace": [
 {'$var1': 'foo', '%var2%': 'bar'},
  '$var1 is %var2%'
]}</programlisting>
      <para>Returns <literal>"foo is bar"</literal>.</para>
    </section>
  </section>
  <section xml:id="fn-resourcefacade">
    <?dbhtml stop-chunking?>
    <title>Fn::ResourceFacade</title>
    <variablelist role="definition_list">
      <varlistentry>
        <term>When writing a Template Resource:</term>
        <listitem>
          <itemizedlist>
            <listitem>
              <para>user writes a template that will fill in for a resource (the resource is the facade).</para>
            </listitem>
            <listitem>
              <para>when they are writing their template they need to access the metadata from
the facade.</para>
            </listitem>
          </itemizedlist>
        </listitem>
      </varlistentry>
    </variablelist>
    <section xml:id="id17">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term role="String">attribute_name</term>
          <listitem>
            <para>One of <literal>Metadata</literal>, <literal>DeletionPolicy</literal> or <literal>UpdatePolicy</literal>.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id18">
      <title>Usage</title>
      <programlisting>{'Fn::ResourceFacade': 'Metadata'}
{'Fn::ResourceFacade': 'DeletionPolicy'}
{'Fn::ResourceFacade': 'UpdatePolicy'}</programlisting>
    </section>
    <section xml:id="example">
      <title>Example</title>
      <para>Here is a top level template <literal>top.yaml</literal></para>
      <programlisting>resources:
  my_server:
    type: OS::Nova::Server
    metadata:
      key: value
      some: more stuff</programlisting>
      <para>Here is a resource template <literal>my_actual_server.yaml</literal></para>
      <programlisting>resources:
  _actual_server_:
    type: OS::Nova::Server
    metadata: {'Fn::ResourceFacade': Metadata}</programlisting>
      <para>The environment file <literal>env.yaml</literal></para>
      <programlisting>resource_registry:
  resources:
    my_server:
      "OS::Nova::Server": my_actual_server.yaml</programlisting>
      <para>To use it</para>
      <programlisting>$ heat stack-create -f top.yaml -e env.yaml</programlisting>
      <para>What happened is the metadata in <literal>top.yaml</literal> (key: value, some: more
stuff) gets passed into the resource template via the <link linkend="fn-resourcefacade">Fn::ResourceFacade</link>
function.</para>
    </section>
  </section>
  <section xml:id="fn-memberlisttomap">
    <?dbhtml stop-chunking?>
    <title>Fn::MemberListToMap</title>
    <para>Convert an AWS style member list into a map.</para>
    <section xml:id="id19">
      <title>Parameters</title>
      <variablelist role="definition_list">
        <varlistentry>
          <term>key name: string</term>
          <listitem>
            <para>The name of the key (normally "Name" or "Key").</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>value name: string</term>
          <listitem>
            <para>The name of the value (normally "Value").</para>
          </listitem>
        </varlistentry>
        <varlistentry>
          <term>list: A list of strings</term>
          <listitem>
            <para>The string to convert.</para>
          </listitem>
        </varlistentry>
      </variablelist>
    </section>
    <section xml:id="id20">
      <title>Usage</title>
      <programlisting>{'Fn::MemberListToMap': ['Name', 'Value', ['.member.0.Name=key',
                                           '.member.0.Value=door',
                                           '.member.1.Name=colour',
                                           '.member.1.Value=green']]}</programlisting>
      <para>Returns <literal>{'key': 'door', 'colour': 'green'}</literal>.</para>
    </section>
  </section>
</chapter>