Summary

A Job Queue allow you to set a limit on the maximum number of concurrent jobs that can run within the Queue.

In some cases it may be useful to programmatically change this limit. For example, you may want to set a limit during a certain portion of your processing cycle, but remove the limit during other times.

This article explains how to use the adTempus API to make the changes.

Procedure

You will first create a Script Library that contains supporting code.You will then create jobs that runs the script code.

Create the Script Library

1. In the adTempus Console, expand the Scripts folder, then right-click Script Libraries and choose New Script Library....

2. In the Script Library Properties window:

a. Name the library "QueueLimits"

b. Select "VB.NET" for the Language

c. Erase the default script code and paste in the following code:

Imports System.Collections.Generic 
Imports ArcanaDevelopment.adTempus.Client

Public Module QueueLimits
    'Sets the concurrent job limit for the specified queue.
    'Call with jobLimit=0 for no limit
    'See www.arcanadev.com/support/kb/K00000380.aspx for more information
    Public Sub SetQueueLimit(ByVal queueName As String, ByVal jobLimit As Integer )
        Dim session As Scheduler
		Dim queue As JobQueue
        
		'create a new session to the local adTempus instance
        session = CreateSession()
		
		queue=GetQueue(session,queueName)
		If queue Is Nothing Then
			Throw New System.Exception("The specified Queue could not be found")
		End If
	
		queue.MaxConcurrentJobs=jobLimit
		queue.Save()
		adTempus.LogMessage(MessageTypeEnum.Informational,0,"Job limit for Queue """ & queueName & """ set to " & jobLimit)

    End Sub


	'Finds the Queue with the specified name
    Private Function GetQueue(ByVal session As Scheduler, ByVal queueName As String) As JobQueue
		Dim queues As ADTObjects
		queues=session.GetObjectsForClass(ClassIDEnum.CID_JobQueue)
		For Each queue As JobQueue In queues
			If String.Compare(queue.Name,queueName,True)=0 Then
				Return queue
			End If
		Next
		Return Nothing
		
    End Function

	'Creates a new session with the local adTempus instance.
    Private Function CreateSession() As Scheduler
        Dim app As Application
        app = New Application

        'create a new session to the local adTempus instance
        Return app.Connect("", "")
    End Function
End Module

d. Click OK to save the Script Library.

Set Limits from a Script

Once the Script Library has been created you can call the SetQueueLimit method from an adTempus script to set the conccurrent execution limit for a queue.

To use the code defined in the Script Library:

1. Create a new job, or edit an existing job. Keep in mind the following points:

• The new limit will only affect jobs that are submitted for execution after the change is made. The job that runs the script will not be affected, as it will already be running when the change is made.
• The script uses the adTempus API to update the variables. The API is subject to the same security checks as the adTempus Console. Therefore you must run the job under the User Account of a user who has permission within adTempus to modify the Queue that you are updating.

2. On the Steps page of the Job Properties, add a new step, selecting the "Execute a script" option in the Select Task window.

3. In the Script Execution Task Properties window, select the "Execute a script stored in adTempus" option, then click the Select... button.

4. In the Select Script window, click New... to create a new script.

5. In the Script Properties window, select "VB.NET" as the script Language.

6. Under Included Script Libraries, check the "QueueLimits" library.

7. To set the limit call the SetQueueLimit method using the following syntax:

where QueueName is the name of the queue you want to update and JobLimit is the concurrent job limit. Specify a JobLimit of 0 to remove all limits.

The following script sets the limit for the "Default" queue to 2 concurrent jobs:

Imports System
Imports System.Collections
Imports ArcanaDevelopment.adTempus.Server

Public Class UserScript
    Inherits ArcanaDevelopment.adTempus.ScriptEngine.UserScriptBase

    Public Overrides Function Run() As Object
        SetQueueLimit("Default",2)
        Return 0
    End Function
End Class

You can then create another job to reset the limit at the end of the processing cycle, if desired. The following code removes the limit:

Imports System
Imports System.Collections
Imports ArcanaDevelopment.adTempus.Server

Public Class UserScript
    Inherits ArcanaDevelopment.adTempus.ScriptEngine.UserScriptBase

    Public Overrides Function Run() As Object
        SetQueueLimit("Default",0)
        Return 0
    End Function
End Class