Support user task listeners

[barmac]

What should we do?

Implement user task listeners in Camunda 8

<userTask id="my_user_task" name="my_user_task">
 <extensionElements>
   <zeebe:userTask/>
   <zeebe:taskListeners>
     <zeebe:taskListener eventType="create" type="create_listener" retries="2"/>
     <zeebe:taskListener eventType="assignment" type="assignment_listener"/>
     <zeebe:taskListener eventType="update" type="update_listener" retries="8"/>
     <zeebe:taskListener eventType="complete" type="complete_listener"/>
   </zeebe:taskListeners>
   <zeebe:priorityDefinition/>
   <!--other extension props e.g. assignmentDefinition, priorityDefinition-->
 </extensionElements>
 <!--other props-->
</userTask>

• I can define task listeners on user task
  • type (string, FEEL expression)
  • eventType: complete, assignment
  • retries (string, FEEL expression, default is 3)
• TLs can be used in Camunda 8.7 or newer
• When I switch from Zeebe user task to job worker, the task listeners are removed

Projects:

• feat: support zeebe:TaskListener zeebe-bpmn-moddle#67
• Support zeebe:TaskListener camunda-bpmn-js-behaviors#88
• feat: add task listeners for Zeebe bpmn-io/bpmn-js-properties-panel#1088
• feat: support task listeners bpmnlint-plugin-camunda-compat#181
• Support task listeners linting#123

Why should we do it?

Product hub epic: https://github.com/camunda/product-hub/issues/1316

[barmac]

This is blocked until we clarify the XML structure: https://camunda.slack.com/archives/C0622NWC9LK/p1729161860084329

[barmac]

We clarified the XML structure, but the list of event types needs to be decided upon yet: https://github.com/camunda/product-hub/issues/1822#issuecomment-2419645986

[barmac]

The duplicate listeners won't be rejected by the engine as decided in https://camunda.slack.com/archives/C0622NWC9LK/p1729762326243379?thread_ts=1729176573.663119&cid=C0622NWC9LK
We may consider to have a warning though as it's hard to imagine anybody defines duplicates on purpose.

[barmac]

I updated the event types according to https://camunda.slack.com/archives/C0622NWC9LK/p1730303397300139?thread_ts=1730288591.575289&cid=C0622NWC9LK
Note that the stretch goal is to support more events, so it's not fixed yet.

[barmac]

Task listeners on process are out of scope: https://camunda.slack.com/archives/C0622NWC9LK/p1730311452811039?thread_ts=1730288591.575289&cid=C0622NWC9LK

[barmac]

This is ready now.

[barmac]

We could use this BPMN as an example to open once the feature is implemented:

user-task-listener.bpmn.txt

[misiekhardcore]

@barmac what do you mean? where do you want to put this file?

[barmac]

I prepared this as an example BPMN (cf. https://camunda.slack.com/archives/C0622NWC9LK/p1730909451217819). There's no need to include it anywhere in the source code, but we can use it as way to verify the solution.

[barmac]

We could use this BPMN as an example to open once the feature is implemented:

user-task-listener.bpmn.txt

The file was broken, but replaced it with a fixed one.

[misiekhardcore]

@barmac All the parts of this issue are now done. What are the next steps?

[barmac]

As the feature is implemented in the upstream libraries, we can now move the issue to fixed upstream. Then, to close it, we will need to open and merge a pull request which integrates the respective dependency updates into the Modeler.

[barmac]

I will open an integration PR for this once #4620 is merged.