CODEWITHSUNDEEP
camunda
Dorian McAllister
Dorian McAllister

Reputation: 785

How to update MultiInstance User Task to add/delete Tasks?

We have a business scenario where we would like to have the ability to INCREASE or DELETE tasks within a multi-instance context. I’ve managed to successfully create a mutli-instance User task based on a collection workPartnerList

If a Process is working on a multi instance stage of the workflow - how can I increase or decrease the multi instance state based on the count/values of workPartnerList which can increase or decrease based on updates from the API call. (we need to do this prior to the overall task completion)?

Upvotes: 1

Views: 1971

Answers (1)

rob2universe
rob2universe

Reputation: 7618

I assume you are referring to a parallel multi-instance task.

https://docs.camunda.org/manual/latest/reference/bpmn20/tasks/task-markers/

Another way to define the number of instances is to specify the name of a process variable which is a collection using the loopDataInputRef child element. For each item in the collection, an instance will be created

The creation of the instances happens at the point in time when the execution reaches the parallel multi-instance activity. The number of instances created is determined by the size of the collection at this specific point in time. (A BPMN2 process engine will not automatically keep the task instances in sync with the collection.)

To "delete" task instance you can complete or cancel them (e.g. via an attached boundary event) or us the completion condition.

A multi-instance activity ends when all instances are finished. However, it is possible to specify an expression that is evaluated every time one instance ends. When this expression evaluates to true, all remaining instances are destroyed and the multi-instance activity ends, continuing the process. Such an expression must be defined in the completionCondition child element.

To add additional task instances to a running process instance dynamically you can use for instance event sub processes or attach a boundary event to the task.

https://docs.camunda.org/manual/7.13/reference/bpmn20/events/message-events/#message-boundary-event

Boundary events are catching events that are attached to an activity. This means that while the activity is running, the message boundary event is listening for named message. When this is caught, two things might happen, depending on the configuration of the boundary event:

Interrupting boundary event: The activity is interrupted and the sequence flow going out of the event is followed.

Non-interrupting boundary event: One token stays in the activity and an additional token is created which follows the sequence flow going out of the event.

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If you are willing to approach this on API level then the TaskService allows you to create a new task (with a user defined task id). Example: https://github.com/rob2universe/cam-multi-instance/blob/25f524be6a112deb1b4ae3bb4f28a35422e428e0/src/test/java/org/camunda/bpm/example/ProcessJUnitTest.java#L79

The migration API would even allow you to add additional instances to the already created set of task instances - see: https://docs.camunda.org/manual/latest/user-guide/process-engine/process-instance-modification/#modify-multi-instance-activity-instances

Upvotes: 2

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