Chapter 8. Timers
You can use timers to trigger logic after a certain period or to repeat specific actions at regular intervals. Timers wait for a predefined amount of time before triggering once or repeatedly.
8.1. Supported timers for Red Hat Process Automation Manager
Red Hat Process Automation Manager supports two types of timers:
- Quartz: Recommended for use with Spring Boot and Tomcat
- EJB: Recommended for use with Red Hat JBoss EAP, both on-premise and Red Hat OpenShift Container Platform
Do not use timers for the following business strategies:
- Do not use timers as your process polling strategy. For example, instead of directly calling the external service and adding a 1 second timer, use Fuse to register an asynchronous route. Use the Fuse callback to fire an event for the process to move on once the expected response is received. Create a work item handler as part of your business strategy outside of your Business Process Model and Notation (BPMN) process model and move the timer to the work item handler.
- Do not use timers to enforce safe points or commits during process execution. Timers are designed to represent a period of time (duration) in a business process and not for enforcing engine-specific behavior.
8.2. Configuring timers with delay and period
You can set a timer with delay and a certain period. The delay specifies the waiting time after the node activation, and the period defines the time between the subsequent trigger activation. The period value 0 results in a one-shot timer. You can specify the delay and period expression in [#d][#h][#m][#s][#[ms]] form, indicating the number of days, hours, minutes, seconds, and milliseconds (default). For example, the expression 1h indicates one hour waiting time before triggering the timer again.
8.3. Configuring timers with ISO-8601 date format
You can configure timers with ISO-8601 date format that supports both one-shot timers and repeatable timers. You can define timers as date and time representation, time duration, or repeating intervals. For example:
-
Date
2020-12-24T20:00:00.000+02:00signifies that timer is triggered exactly on Christmas at 8:00 p.m. -
Duration
PT1Ssignifies that timer is triggered once after one second. -
Repeating intervals
R/PT1Ssignifies that timer is triggered every second with any limit. Alternatively,R5/PT1Striggers the timer five times every second.
8.4. Configuring timers with process variables
You can also specify timers using process variables, consisting of the string representation of delay and period or ISO8601 date format. When you specify #{variable}, the engine parses the expression and replaces the expression value with the variable. In a process, you can use timers using the following ways:
- Add a timer event to a process flow. The process activation starts the timer and when the timer is triggered (once or repeatedly), it activates the successor of the timer node. Subsequently, the outgoing connection of a timer with a positive period value is triggered multiple times. When a timer node is canceled, the associated timer is also canceled and no more triggers occur.
- Associate timer as a boundary event with a sub-process or task.
8.5. Updating timers in a running process instance
In some cases, the scheduled timer needs to be rescheduled to accommodate the new requirements, such as changing delay, period, or repeat limit. Updating a timer includes many low-level operations, therefore, Red Hat Process Automation Manager provides the following command to perform the low-level operations related to updating a timer as an atomic operation. The following command ensures that all the operations are performed within the same transaction.
org.jbpm.process.instance.command.UpdateTimerCommand
Only boundary timer events and intermediate timer events are supported to update.
You can reschedule the timer by specifying the two mandatory parameters and one of the three optional parameter sets of the UpdateTimerCommand class.
| Parameter or parameter set | Type |
|---|---|
| process instance ID (Mandatory) |
|
| timer node name (Mandatory) |
|
| delay (Optional) |
|
| period (Optional) |
|
| repeat limit (Optional) |
|
Example rescheduling time event
// Start the process instance and record its ID: long id = kieSession.startProcess(BOUNDARY_PROCESS_NAME).getId(); // Set the timer delay to 3 seconds: kieSession.execute(new UpdateTimerCommand(id, BOUNDARY_TIMER_ATTACHED_TO_NAME, 3));
