CallActivity.md

CallActivity

• Behaviour
  • Passing input to the called process
    • Multi-instance loop context

Behaviour

Call activity will wait for called process to complete.

Process defined in the same definition can be started. If the process is not found the call activity expects to be signaled or cancelled.

Emits activity.call event with calledElement property containing the id of the process. Expressions can be used to resolve the calledElement property value.

If the call activity is cancelled the target process is discarded.

If the target process is discarded the call activity is cancelled.

If the target process throws the call activity is errored. The call activity can catch the error with a boundary error event.

Passing input to the called process

If the call activity run message carries an input property, it is forwarded to the called process and seeded as environment.variables.input, so the called process and its activities can resolve ${environment.variables.input}.

The call activity does not populate input itself — set it during formatting, e.g. from an extension that publishes a format message on enter:

function callInput(activity) {
  if (activity.type !== 'bpmn:CallActivity') return;
  return {
    activate() {
      activity.broker.subscribeTmp(
        'event',
        'activity.enter',
        () => {
          activity.broker
            .getQueue('format-run-q')
            .queueMessage({ routingKey: 'run.input.format' }, { input: { shoeSize: 42 } }, { persistent: false });
        },
        { noAck: true, consumerTag: '_call-input' }
      );
    },
    deactivate() {
      activity.broker.cancel('_call-input');
    },
  };
}

The same applies to an embedded sub process: format input onto the sub process (use the same extension, gated on activity.type === 'bpmn:SubProcess') and it is seeded as environment.variables.input for the sub process execution and its child activities.

Multi-instance loop context

A multi-instance call activity or sub process seeds environment.variables.input of each iteration with its loop context — an object with isSequential, index, and cardinality, plus the iteration item under the loop elementVariable name (default item) for a collection loop. The iteration can then resolve e.g. ${environment.variables.input.item} or ${environment.variables.input.index}.

Any input already formatted onto the iteration content is incorporated into this object and takes precedence over the loop context keys on conflict.