December | 2018

Here at work, we’re working on a migration project, from Jenkins (which we’ve been using as a scheduler) to JAMS Scheduler. In Jenkins we have a lot of Groovy scripts, and we have them in source control. So, to make the migration as effortless as possible, we wanted to use them “as-is”, right out of source control.

The solution I found was:

On the JAMS agent, install the subversion command line client
Also on the JAMS agent, install groovy
Create a job that gets (“checks out”) the latest scripts every evening from source control in a specific directory; let’s call it c:\jobs
Create a JAMS Execution Method called Groovy (see below)
Create the Jenkins jobs in JAMS, one by one. In the source box, only write the full path of the groovy script, e.g. c:\jobs\TransferOrders.groovy

#4 is where the magic happens. The execution method is defined as a Powershell method. In the template, there’s code that (suprise) calls groovy. The powershell code is the following (see if you can spot a couple of tricks):

#
# Source: DotJim blog (https://dandraka.com)
# Jim Andrakakis, December 2018
#
Import-Module JAMS

# the job's source is supposed to contain ONLY 
# the full path to the groovy script, without quotes
$groovy = "C:\app\groovy-2.5.4\bin\groovy.bat"
$groovyScript="<<JAMS.Current.Source>>"

Write-Host "[JAMS-GROOVY] Running script $groovyScript via $groovy"
if ((Test-Path -Path $groovy) -ne $true)
{
	Write-Error "[JAMS-GROOVY] Groovy executable $groovy not found, is Groovy installed?"
}
if ((Test-Path -Path $groovyScript) -ne $true)
{
	Write-Error "[JAMS-GROOVY] Source file $groovyScript not found"
}

$currentJob = Get-JAMSEntry {JAMS.JAMSEntry} 
$currentJobParams = $currentJob.Parameters
$currentJobParamNames = $currentJobParams.Keys

foreach($n in $currentJobParamNames)
{
	[string]$v = $currentJobParams[$n].Value
	
	# look for replacement tokens
	# in the form of <<ParamName>>
	foreach($r in $currentJobParamNames)
	{
		if ($v.Contains("<<$r>>"))
        {
            [string]$replVal = $currentJobParams[$r].Value
            $v = $v.Replace("<<$r>>", $replVal)
        }
	}
	
	Write-Host "[JAMS-GROOVY] Setting parameter $n = $v"
	[Environment]::SetEnvironmentVariable($n, $v, "Process")
}

# execute the script in groovy
& $groovy $groovyScript

Write-Host "[JAMS-GROOVY] script finished"

Two tricks to note here:

Almost all our groovy scripts have parameters; Jenkins inserts the parameters as environment variables so the scripts can do:

myVar = System.getenv()['myVar']

The first powershell loop does exactly that; it maps all the job’s parameters, defined or inherited, as environment variables, so the scripts can continue to work happily, no change needed.

The second trick is actually an enhancement. As the scripts get promoted though our environments (development > test > integration test > production) some parts of the parameters change –but not all of them.

For example, let’s say there’s a parameter for an inputDirectory.
In the development server, it has the value c:\documents\dev\input. In test, it’s c:\documents\test\input, in integration test it’s c:\documents\intg\input and in production c:\documents\prod\input.

What we can do now is have a folder-level parameter, defined on the JAMS folder where our job definitions are –which is not transferred from
environment to environment. And we can have job-defined parameters that, using the familiar JAMS <<param>> notation, get their values substituted.

So, for example, let’s say I define a folder parameter named “SERVERLEVEL”, which will have the value of “dev” in development, “test” in test etc. In the job, I define another parameter called inputDirectory. This will have the value c:\documents\<<SERVERLEVEL>>\input.

Et voilà! Now we can promote the jobs from environment to environment, completely unchanged. In Jenkins we couldn’t do that; we had to define different values for parameters in dev, in test etc.

Here’s the export xml of the execution method:

<?xml version="1.0" encoding="utf-8"?>
<JAMSObjects>
  <method
    name="Groovy"
    type="Routine">
    <description><![CDATA[Run a pre-fetched groovy script. The job's source should contain the full path to the groovy script.

Note: in the "Bad regex pattern", the execution methon looks for "Caught:" to try to undertand whether 
groovy encountered an exception or not. Here's an example of the groovy output of a script where
an unhandled exception occured:

Hello, world!
Caught: java.lang.NullPointerException: Cannot invoke method test() on null object
java.lang.NullPointerException: Cannot invoke method test() on null object
        at test1.run(test1.groovy:4)]]></description>
    <template><![CDATA[Import-Module JAMS

# the job's source is supposed to contain ONLY 
# the full path to the groovy script, without quotes
$groovy = "C:\app\groovy-2.5.4\bin\groovy.bat"
$groovyScript="<<JAMS.Current.Source>>"

Write-Host "[JAMS-GROOVY] Running script $groovyScript via $groovy"
if ((Test-Path -Path $groovy) -ne $true)
{
	Write-Error "[JAMS-GROOVY] Groovy executable $groovy not found, is Groovy installed?"
}
if ((Test-Path -Path $groovyScript) -ne $true)
{
	Write-Error "[JAMS-GROOVY] Source file $groovyScript not found"
}

$currentJob = Get-JAMSEntry {JAMS.JAMSEntry} 
$currentJobParams = $currentJob.Parameters
$currentJobParamNames = $currentJobParams.Keys

foreach($n in $currentJobParamNames)
{
	[string]$v = $currentJobParams[$n].Value
	
	# look for replacement tokens
	# in the form of <<ParamName>>
	foreach($r in $currentJobParamNames)
	{
		if ($v.Contains("<<$r>>"))
        {
            [string]$replVal = $currentJobParams[$r].Value
            $v = $v.Replace("<<$r>>", $replVal)
        }
	}
	
	Write-Host "[JAMS-GROOVY] Setting parameter $n = $v"
	[Environment]::SetEnvironmentVariable($n, $v, "Process")
}

# execute the script in groovy
& $groovy $groovyScript

Write-Host "[JAMS-GROOVY] script finished"]]></template>
    <properties>
      <property
        name="HostAssemblyName"
        typename="System.String"
        value="JAMSPSHost" />
      <property
        name="HostClassName"
        typename="System.String"
        value="MVPSI.JAMS.Host.PowerShell.JAMSPSHost" />
      <property
        name="StartAssemblyName"
        typename="System.String"
        value="" />
      <property
        name="StartClassName"
        typename="System.String"
        value="" />
      <property
        name="EditAssemblyName"
        typename="System.String"
        value="" />
      <property
        name="EditClassName"
        typename="System.String"
        value="" />
      <property
        name="ViewAssemblyName"
        typename="System.String"
        value="" />
      <property
        name="ViewClassName"
        typename="System.String"
        value="" />
      <property
        name="BadPattern"
        typename="System.String"
        value="^Caught\:" />
      <property
        name="ExitCodeHandling"
        typename="MVPSI.JAMS.ExitCodeHandling"
        value="ZeroIsGood" />
      <property
        name="GoodPattern"
        typename="System.String"
        value="" />
      <property
        name="SpecificInformational"
        typename="System.String"
        value="" />
      <property
        name="SpecificValues"
        typename="System.String"
        value="" />
      <property
        name="SpecificWarning"
        typename="System.String"
        value="" />
      <property
        name="Force32Bit"
        typename="System.Boolean"
        value="false" />
      <property
        name="ForceV2"
        typename="System.Boolean"
        value="false" />
      <property
        name="HostLocally"
        typename="System.Boolean"
        value="false" />
      <property
        name="Interactive"
        typename="System.Boolean"
        value="false" />
      <property
        name="NoBOM"
        typename="System.Boolean"
        value="false" />
      <property
        name="SourceFormat"
        typename="MVPSI.JAMS.SourceFormat"
        value="Text" />
      <property
        name="EditAfterStart"
        typename="System.Boolean"
        value="false" />
      <property
        name="EditSource"
        typename="System.Boolean"
        value="false" />
      <property
        name="Extension"
        typename="System.String"
        value="ps1" />
      <property
        name="JobModule"
        typename="System.String"
        value="" />
      <property
        name="SnapshotSource"
        typename="System.Boolean"
        value="false" />
      <property
        name="Redirect"
        typename="MVPSI.JAMS.Redirect"
        value="All" />
      <property
        name="HostSubDirectory"
        typename="System.String"
        value="" />
      <property
        name="HostExecutable"
        typename="System.String"
        value="JAMSHost.exe" />
    </properties>
  </method>
</JAMSObjects>

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Monthly Archives: December 2018

Signs that you need coffee, #3

Running Groovy scripts in JAMS Scheduler

I’d be delighted to be proven wrong, but…

Software, Greece, Switzerland. And coffee. LOTS of coffee !