test

N1 Service Provisioning System 4.1 Reference Guide

try Step Examples

Suppose you have a component whose installation consists of resource deployment followed by a restart. In this case, the component is really considered 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>

Try blocks can also be used to model intelligent auto-upgrades. Suppose you are working with version 1.1 of a component, and you have two different install routines depending on whether version 1.0 was previously installed or not (fresh install versus upgrade install). On can model this in a single install block, as follows: 


<installSteps blockName="default">
	<try>
		<block>
			<checkDependency>
				<installedComponent name="foo" version="1.0"/>
			</checkDependency>
			<!-- 1.0 install exists, do upgrade -->
		</block>
		<catch>
			<!-- 1.0 install doesn"t exist, do fresh install -->
		</catch>
	</try>
</installSteps>

The <finally> block is most often used to cleanup temporary resources. The following example creates a temp 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>