The Workflow Scheduler

The Imixs WorkflowScheduler provides a TimerService to schedule workitems based on scheduled Workflow Events. A scheduled Workflow Event can be defined using the Imixs-BPM Modeler by the property tab ‘Timer’. If a workitem is in a status where scheduled events are defined, the WorkflowScheduler will process this workitem automatically based on the model definition. The Workflow Scheduler can be used to automatically process workflow tasks - e.g. a reminder or a escalation task.

The Configuration

The WorkflowSchedulerService expects the scheduling configuration document. The scheduling configuration defines the timer interval to run the workflow scheduler.

A timer configuration can be created with the following item definitions:

<document xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema">
       <item name="type">
            <value xsi:type="xs:string">configuration</value>
        </item> 
       <item name="txtname">
            <value xsi:type="xs:string">org.imixs.workflow.scheduler</value>
        </item> 
       <item name="txtconfiguration">
            <value xsi:type="xs:string">hour=*</value>
            <value xsi:type="xs:string">minute=30</value>
        </item>
        <item name="_enabled">
            <value xsi:type="xs:boolean">true</value>
        </item>  
</document>

Scheduling

The Imixs WorkflowSchedulerService uses a calendar-based syntax for scheduling based on the EJB 3.1 Timer Service specification. The syntax takes its roots from the Unix cron utility. The following attributes can be stored in the txtConfiguration property of the workflowScheulderSercice configuration:

Attriubte Description Possible Values Default Value
second One or more seconds within a minute [0,59] 0
minute One or more minutes within a hour [0,59] 0
hour One or more hours within a day [0,23] 0
dayOfMonth One or more days
within a month
[1,31] or “1st”,“2nd”,“3rd”,….
or “Sun”,“Mon”,“Tue”,“Wed”,“Thu”,“Fri”,“Sat”
or “Last” (the last day in month)
or -x (means x day(s) before the last day of
or the month
*
month One or more month within a year [1,12] or “Jan”,“Feb”,“Mar”,“Apr”,“May”,
“Jun”,“Jul”,“Aug”,“Sep”,“Oct”,“Nov”,“Dec”
*
dayOfWeek One or more days within a week [1,7] or “Sun”,Mon“,”Thu“,”Wed“,”Thu“,”Fri“,”Sat“ ”0“ and ”7" refer to Sunday! *
year A paticular year 4 digit calendar year *
timezone A specific time zone see time zoneinof (or tz) database *
start Start date yyyy/mm/dd
end End date yyyy/mm/dd

Each attribute of an expression supports values in different formats. For example you can define a list of days or a range of years. The the following table with suported value formats:

Format Description Example
Single Value only one possible value year=“2009” or month=“May”
Wildcard all possible values year=““ or dayOfWeek=”
List two or more values year=“2014,2015” or dayOfWeek=“Sat,Sun”
Range range of values second=“1-10” or dayOfWeek=“Mon-Fri”
Increments startignpoint and increment minute=“*/15” or second=“30/10”

So you can configure the scheduler is several ways. Here a some typical exampls for possible configuration:

Every hour

hour=*

Every five minutes with the hour

minute=*/15
hour=*

Every hour from Monday to Friday

hour=*
dayOfWeek=1-5

Every 30 minutes with the hours from 8:00 AM to 5:00 PM, from Monday to Friday

minute=*/30
hour=8-17
dayOfWeek=1-5

Only Sunday on 1:00 AM

hour=1
dayOfWeek=7

The scheudler information is stored in the property ‘txtConfiguration’ as a String List. The configuration entity for the WorkflowSchedulerService holds the following additional information.

property type description
$uniqueid String defines the unique ID the for the corresponding TimerService
txtConfiguration String List Holds information about the calendar based scheduling
statusmessage String last status message (read only)
Schedule String scheduling information (read only)
nextTimeout Date Timestamp for next timeout
timeRemaining Long milisecnds until next timeout
datLastRun Date Timestamp of last sucessfull run (read only)
numInterval int optional- timer interval if no txtConfiguration is defined
datStart Date optional- start date for timer if no txtConfiguration is defined
datStop Date optional- stop date for timer if no txtConfiguration is defined

Note: The properties “statusmessage”, “schedule”, “nextTimeout” and “timeRemaining” are read only and will be updated computed if the method findConfiguration() was called.

Ignored Workitems

The WorkflowSchedulerService processes all kinds of workitems which are assigned to a valid workflow model definition with scheduled events. A workitem is ignored by the WorkflowSchedulerService only in case the workitem type ends with the sufix ‘deleted’

type=workitemdeleted

or the workitem is marked as immutable

$immutable=true

See the DocumentService for details.

The WorkflowSchedulerService EJB

The WorkflowSchedulerService EJB implements the following methods:

public ItemCollection loadConfiguration() ;

public ItemCollection saveConfiguration(ItemCollection configItemCollection)
       throws AccessDeniedException;

public ItemCollection start() throws AccessDeniedException;

public ItemCollection stop() throws AccessDeniedException ;

public boolean isRunning();

The methods “loadConfiguration()” and “saveConfiguration()” can be used to lookup or update the current workflow scheduler configuration entity. The methods “start()” and “stop()” can be used to start or stop the timer service. The method “isRunning()” returns true if the TimerService was started. If the workflowScheduler was started the timerService can be identified by the $UniqueID of the scheduler configuration entity.

Security & Deployment

The ScheduledWorkflowService EJB is embedded into the security concepts of the Imixs Workflow Engine. As the ScheduledWorkflowService needs full access rights to all workitems to perform a scheduled activity the EJB is annotated with the @RunAs declaration:

@DeclareRoles( { "org.imixs.ACCESSLEVEL.MANAGERACCESS" })
@Stateless
@RunAs("org.imixs.ACCESSLEVEL.MANAGERACCESS")
@Remote(org.imixs.workflow.jee.ejb.WorkflowScheduler.class)
public class WorkflowSchedulerService implements WorkflowSchedulerServiceRemote {
 ....
}

This means that the WorkflowSchedulerService EJB need to be deployed with sufficient security role mappings. For Glassfish it is necessary to declare a principal-name which will be used by the EJB Container calling the @TimeOut method. You can use the glassfish specific glassfish-application.xml deployment descriptor in the jee module. To declare a principal-name with manager access use the following example where the userID “IMIXS-WORKFLOW-Service” is mapped to the Role “org.imixs.ACCESSLEVEL.MANAGER” in the realm “imixsrealm”:

<glassfish-application>
....
    <security-role-mapping>
        <role-name>org.imixs.ACCESSLEVEL.MANAGERACCESS</role-name>
        <group-name>Manager</group-name>
        <principal-name>IMIXS-WORKFLOW-Service</principal-name>
    </security-role-mapping>
    <realm>imixsrealm</realm>
 ...
</glassfish-application>

So in this case the TimerService will be performed by the user “Manfred”.

Note: Be careful to declare this role and principal-name with care and a setting which is reasonable in your server environment. For example use a reserved user account like “IMIXS-WORKFLOW-Service” which is not used by persons in your organization.

galssfish-ejb-jar.xml

Using the galssfish-ejb-jar.xml descriptor it is also necessary to add a principal user to the ejb declaration which will be associate to the @RunAs annotation. If no principal is defined in galssfish-ejb-jar.xml, the application server uses a principal from the security-role-mapping. If there is only one principal associated with the role, that principal will be taken as the default run-as principal value. But if there is more than one principal associated with the role, you need to explicitly set the run-as principal in the galssfish-ejb-jar.xml. The following example demonstrates setting the run-as principal in galssfish-ejb-jar.xml:

 ...
<ejb>
    <ejb-name>WorkflowSchedulerService</ejb-name>
    <principal>
       <name>IMIXS-WORKFLOW-Service</name>
    </principal>
</ejb>
 ...