<finally> Element

A child element of the <try> step. <finally> specifies the steps to execute regardless of whether a typical error occurred earlier within the <try> or <catch> steps. An atypical error can be a plan abort or a plan timeout, in which case the steps of the <finally> element are skipped. <finally> can contain any number of steps that are permitted within the scope of the block that contains the <try> step.

The <finally> element is used primarily to specify cleanup steps that should always be run regardless of an error. To run cleanup steps in response to an error, put them in the <catch> element instead.

Example 2–6 Using the <try> Step

In this example, the component installation consists of resource deployment followed by a restart. In this case, the component is considered to be installed after its resources are deployed, and a failure during restart should not affect its installed state. Typical errors can be suppressed during the restart as follows:

<installSteps blockName="default">
    <deployResource/>
    <try>
        <block>
            <call blockName="restart"><thisComponent/></call>
        </block>
        <catch/><!-- suppress all typical errors -->  
    </try>
</installSteps>

You can use <try> blocks to model intelligent auto-upgrades. Version 1.1 of a component has two different installation routines. One performs a fresh installation of the component. The other performs an upgrade installation if Version 1.0 of that component was previously installed. You can model this situation in a single installation block, as follows:

<installSteps blockName="default">
    <try>
        <block>
          <checkDependency>
              <installedComponent name="foo" version="1.0"/>
          </checkDependency>
          <!-- 1.0 installation exists, do upgrade -->
        </block>
        <catch>
          <!-- 1.0 installation doesn't exist, do fresh installation -->
        </catch>
    </try>
</installSteps>

The <finally> block is most often used to clean up temporary resources. The following example creates a temporary file, processes it, and then removes it.

<control blockName="default">
    <varList>
        <var name="file" default="/tmp/file.txt"/>
    </varList>
    <execNative outputFile=":[file]">
        <exec cmd="ls"><arg value="-l"/></exec>
    </execNative>
    <try>
        <block>
            <!-- process file in some way -->
        </block>
        <finally>
            <execNative>
                <exec cmd="rm"><arg value=":[file]"/></exec>
            </execNative>
        </finally>
    </try>
</control>