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 returns the Base64 representation of the input string.</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>{Base64: "convert this string please."}</programlisting>
      <para>Returns the Base64 of the 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>